/* * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "code/icBuffer.hpp" #include "gc_implementation/g1/bufferingOopClosure.hpp" #include "gc_implementation/g1/concurrentG1Refine.hpp" #include "gc_implementation/g1/concurrentG1RefineThread.hpp" #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" #include "gc_implementation/g1/g1AllocRegion.inline.hpp" #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" #include "gc_implementation/g1/g1CollectorPolicy.hpp" #include "gc_implementation/g1/g1ErgoVerbose.hpp" #include "gc_implementation/g1/g1EvacFailure.hpp" #include "gc_implementation/g1/g1GCPhaseTimes.hpp" #include "gc_implementation/g1/g1Log.hpp" #include "gc_implementation/g1/g1MarkSweep.hpp" #include "gc_implementation/g1/g1OopClosures.inline.hpp" #include "gc_implementation/g1/g1RemSet.inline.hpp" #include "gc_implementation/g1/heapRegion.inline.hpp" #include "gc_implementation/g1/heapRegionRemSet.hpp" #include "gc_implementation/g1/heapRegionSeq.inline.hpp" #include "gc_implementation/g1/vm_operations_g1.hpp" #include "gc_implementation/shared/isGCActiveMark.hpp" #include "memory/gcLocker.inline.hpp" #include "memory/genOopClosures.inline.hpp" #include "memory/generationSpec.hpp" #include "memory/referenceProcessor.hpp" #include "oops/oop.inline.hpp" #include "oops/oop.pcgc.inline.hpp" #include "runtime/aprofiler.hpp" #include "runtime/vmThread.hpp" size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; // turn it on so that the contents of the young list (scan-only / // to-be-collected) are printed at "strategic" points before / during // / after the collection --- this is useful for debugging #define YOUNG_LIST_VERBOSE 0 // CURRENT STATUS // This file is under construction. Search for "FIXME". // INVARIANTS/NOTES // // All allocation activity covered by the G1CollectedHeap interface is // serialized by acquiring the HeapLock. This happens in mem_allocate // and allocate_new_tlab, which are the "entry" points to the // allocation code from the rest of the JVM. (Note that this does not // apply to TLAB allocation, which is not part of this interface: it // is done by clients of this interface.) // Notes on implementation of parallelism in different tasks. // // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism. // The number of GC workers is passed to heap_region_par_iterate_chunked(). // It does use run_task() which sets _n_workers in the task. // G1ParTask executes g1_process_strong_roots() -> // SharedHeap::process_strong_roots() which calls eventuall to // CardTableModRefBS::par_non_clean_card_iterate_work() which uses // SequentialSubTasksDone. SharedHeap::process_strong_roots() also // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). // // Local to this file. class RefineCardTableEntryClosure: public CardTableEntryClosure { SuspendibleThreadSet* _sts; G1RemSet* _g1rs; ConcurrentG1Refine* _cg1r; bool _concurrent; public: RefineCardTableEntryClosure(SuspendibleThreadSet* sts, G1RemSet* g1rs, ConcurrentG1Refine* cg1r) : _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true) {} bool do_card_ptr(jbyte* card_ptr, int worker_i) { bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false); // This path is executed by the concurrent refine or mutator threads, // concurrently, and so we do not care if card_ptr contains references // that point into the collection set. assert(!oops_into_cset, "should be"); if (_concurrent && _sts->should_yield()) { // Caller will actually yield. return false; } // Otherwise, we finished successfully; return true. return true; } void set_concurrent(bool b) { _concurrent = b; } }; class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { int _calls; G1CollectedHeap* _g1h; CardTableModRefBS* _ctbs; int _histo[256]; public: ClearLoggedCardTableEntryClosure() : _calls(0) { _g1h = G1CollectedHeap::heap(); _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); for (int i = 0; i < 256; i++) _histo[i] = 0; } bool do_card_ptr(jbyte* card_ptr, int worker_i) { if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { _calls++; unsigned char* ujb = (unsigned char*)card_ptr; int ind = (int)(*ujb); _histo[ind]++; *card_ptr = -1; } return true; } int calls() { return _calls; } void print_histo() { gclog_or_tty->print_cr("Card table value histogram:"); for (int i = 0; i < 256; i++) { if (_histo[i] != 0) { gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); } } } }; class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure { int _calls; G1CollectedHeap* _g1h; CardTableModRefBS* _ctbs; public: RedirtyLoggedCardTableEntryClosure() : _calls(0) { _g1h = G1CollectedHeap::heap(); _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); } bool do_card_ptr(jbyte* card_ptr, int worker_i) { if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { _calls++; *card_ptr = 0; } return true; } int calls() { return _calls; } }; class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure { public: bool do_card_ptr(jbyte* card_ptr, int worker_i) { *card_ptr = CardTableModRefBS::dirty_card_val(); return true; } }; YoungList::YoungList(G1CollectedHeap* g1h) : _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { guarantee(check_list_empty(false), "just making sure..."); } void YoungList::push_region(HeapRegion *hr) { assert(!hr->is_young(), "should not already be young"); assert(hr->get_next_young_region() == NULL, "cause it should!"); hr->set_next_young_region(_head); _head = hr; _g1h->g1_policy()->set_region_eden(hr, (int) _length); ++_length; } void YoungList::add_survivor_region(HeapRegion* hr) { assert(hr->is_survivor(), "should be flagged as survivor region"); assert(hr->get_next_young_region() == NULL, "cause it should!"); hr->set_next_young_region(_survivor_head); if (_survivor_head == NULL) { _survivor_tail = hr; } _survivor_head = hr; ++_survivor_length; } void YoungList::empty_list(HeapRegion* list) { while (list != NULL) { HeapRegion* next = list->get_next_young_region(); list->set_next_young_region(NULL); list->uninstall_surv_rate_group(); list->set_not_young(); list = next; } } void YoungList::empty_list() { assert(check_list_well_formed(), "young list should be well formed"); empty_list(_head); _head = NULL; _length = 0; empty_list(_survivor_head); _survivor_head = NULL; _survivor_tail = NULL; _survivor_length = 0; _last_sampled_rs_lengths = 0; assert(check_list_empty(false), "just making sure..."); } bool YoungList::check_list_well_formed() { bool ret = true; uint length = 0; HeapRegion* curr = _head; HeapRegion* last = NULL; while (curr != NULL) { if (!curr->is_young()) { gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " "incorrectly tagged (y: %d, surv: %d)", curr->bottom(), curr->end(), curr->is_young(), curr->is_survivor()); ret = false; } ++length; last = curr; curr = curr->get_next_young_region(); } ret = ret && (length == _length); if (!ret) { gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); gclog_or_tty->print_cr("### list has %u entries, _length is %u", length, _length); } return ret; } bool YoungList::check_list_empty(bool check_sample) { bool ret = true; if (_length != 0) { gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", _length); ret = false; } if (check_sample && _last_sampled_rs_lengths != 0) { gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); ret = false; } if (_head != NULL) { gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); ret = false; } if (!ret) { gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); } return ret; } void YoungList::rs_length_sampling_init() { _sampled_rs_lengths = 0; _curr = _head; } bool YoungList::rs_length_sampling_more() { return _curr != NULL; } void YoungList::rs_length_sampling_next() { assert( _curr != NULL, "invariant" ); size_t rs_length = _curr->rem_set()->occupied(); _sampled_rs_lengths += rs_length; // The current region may not yet have been added to the // incremental collection set (it gets added when it is // retired as the current allocation region). if (_curr->in_collection_set()) { // Update the collection set policy information for this region _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); } _curr = _curr->get_next_young_region(); if (_curr == NULL) { _last_sampled_rs_lengths = _sampled_rs_lengths; // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); } } void YoungList::reset_auxilary_lists() { guarantee( is_empty(), "young list should be empty" ); assert(check_list_well_formed(), "young list should be well formed"); // Add survivor regions to SurvRateGroup. _g1h->g1_policy()->note_start_adding_survivor_regions(); _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); int young_index_in_cset = 0; for (HeapRegion* curr = _survivor_head; curr != NULL; curr = curr->get_next_young_region()) { _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); // The region is a non-empty survivor so let's add it to // the incremental collection set for the next evacuation // pause. _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); young_index_in_cset += 1; } assert((uint) young_index_in_cset == _survivor_length, "post-condition"); _g1h->g1_policy()->note_stop_adding_survivor_regions(); _head = _survivor_head; _length = _survivor_length; if (_survivor_head != NULL) { assert(_survivor_tail != NULL, "cause it shouldn't be"); assert(_survivor_length > 0, "invariant"); _survivor_tail->set_next_young_region(NULL); } // Don't clear the survivor list handles until the start of // the next evacuation pause - we need it in order to re-tag // the survivor regions from this evacuation pause as 'young' // at the start of the next. _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); assert(check_list_well_formed(), "young list should be well formed"); } void YoungList::print() { HeapRegion* lists[] = {_head, _survivor_head}; const char* names[] = {"YOUNG", "SURVIVOR"}; for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); HeapRegion *curr = lists[list]; if (curr == NULL) gclog_or_tty->print_cr(" empty"); while (curr != NULL) { gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d", HR_FORMAT_PARAMS(curr), curr->prev_top_at_mark_start(), curr->next_top_at_mark_start(), curr->age_in_surv_rate_group_cond()); curr = curr->get_next_young_region(); } } gclog_or_tty->print_cr(""); } void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) { // Claim the right to put the region on the dirty cards region list // by installing a self pointer. HeapRegion* next = hr->get_next_dirty_cards_region(); if (next == NULL) { HeapRegion* res = (HeapRegion*) Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), NULL); if (res == NULL) { HeapRegion* head; do { // Put the region to the dirty cards region list. head = _dirty_cards_region_list; next = (HeapRegion*) Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); if (next == head) { assert(hr->get_next_dirty_cards_region() == hr, "hr->get_next_dirty_cards_region() != hr"); if (next == NULL) { // The last region in the list points to itself. hr->set_next_dirty_cards_region(hr); } else { hr->set_next_dirty_cards_region(next); } } } while (next != head); } } } HeapRegion* G1CollectedHeap::pop_dirty_cards_region() { HeapRegion* head; HeapRegion* hr; do { head = _dirty_cards_region_list; if (head == NULL) { return NULL; } HeapRegion* new_head = head->get_next_dirty_cards_region(); if (head == new_head) { // The last region. new_head = NULL; } hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, head); } while (hr != head); assert(hr != NULL, "invariant"); hr->set_next_dirty_cards_region(NULL); return hr; } void G1CollectedHeap::stop_conc_gc_threads() { _cg1r->stop(); _cmThread->stop(); } #ifdef ASSERT // A region is added to the collection set as it is retired // so an address p can point to a region which will be in the // collection set but has not yet been retired. This method // therefore is only accurate during a GC pause after all // regions have been retired. It is used for debugging // to check if an nmethod has references to objects that can // be move during a partial collection. Though it can be // inaccurate, it is sufficient for G1 because the conservative // implementation of is_scavengable() for G1 will indicate that // all nmethods must be scanned during a partial collection. bool G1CollectedHeap::is_in_partial_collection(const void* p) { HeapRegion* hr = heap_region_containing(p); return hr != NULL && hr->in_collection_set(); } #endif // Returns true if the reference points to an object that // can move in an incremental collecction. bool G1CollectedHeap::is_scavengable(const void* p) { G1CollectedHeap* g1h = G1CollectedHeap::heap(); G1CollectorPolicy* g1p = g1h->g1_policy(); HeapRegion* hr = heap_region_containing(p); if (hr == NULL) { // null assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p)); return false; } else { return !hr->isHumongous(); } } void G1CollectedHeap::check_ct_logs_at_safepoint() { DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); // Count the dirty cards at the start. CountNonCleanMemRegionClosure count1(this); ct_bs->mod_card_iterate(&count1); int orig_count = count1.n(); // First clear the logged cards. ClearLoggedCardTableEntryClosure clear; dcqs.set_closure(&clear); dcqs.apply_closure_to_all_completed_buffers(); dcqs.iterate_closure_all_threads(false); clear.print_histo(); // Now ensure that there's no dirty cards. CountNonCleanMemRegionClosure count2(this); ct_bs->mod_card_iterate(&count2); if (count2.n() != 0) { gclog_or_tty->print_cr("Card table has %d entries; %d originally", count2.n(), orig_count); } guarantee(count2.n() == 0, "Card table should be clean."); RedirtyLoggedCardTableEntryClosure redirty; JavaThread::dirty_card_queue_set().set_closure(&redirty); dcqs.apply_closure_to_all_completed_buffers(); dcqs.iterate_closure_all_threads(false); gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", clear.calls(), orig_count); guarantee(redirty.calls() == clear.calls(), "Or else mechanism is broken."); CountNonCleanMemRegionClosure count3(this); ct_bs->mod_card_iterate(&count3); if (count3.n() != orig_count) { gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", orig_count, count3.n()); guarantee(count3.n() >= orig_count, "Should have restored them all."); } JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); } // Private class members. G1CollectedHeap* G1CollectedHeap::_g1h; // Private methods. HeapRegion* G1CollectedHeap::new_region_try_secondary_free_list() { MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); while (!_secondary_free_list.is_empty() || free_regions_coming()) { if (!_secondary_free_list.is_empty()) { if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " "secondary_free_list has %u entries", _secondary_free_list.length()); } // It looks as if there are free regions available on the // secondary_free_list. Let's move them to the free_list and try // again to allocate from it. append_secondary_free_list(); assert(!_free_list.is_empty(), "if the secondary_free_list was not " "empty we should have moved at least one entry to the free_list"); HeapRegion* res = _free_list.remove_head(); if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " "allocated "HR_FORMAT" from secondary_free_list", HR_FORMAT_PARAMS(res)); } return res; } // Wait here until we get notifed either when (a) there are no // more free regions coming or (b) some regions have been moved on // the secondary_free_list. SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); } if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " "could not allocate from secondary_free_list"); } return NULL; } HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) { assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, "the only time we use this to allocate a humongous region is " "when we are allocating a single humongous region"); HeapRegion* res; if (G1StressConcRegionFreeing) { if (!_secondary_free_list.is_empty()) { if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " "forced to look at the secondary_free_list"); } res = new_region_try_secondary_free_list(); if (res != NULL) { return res; } } } res = _free_list.remove_head_or_null(); if (res == NULL) { if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " "res == NULL, trying the secondary_free_list"); } res = new_region_try_secondary_free_list(); } if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { // Currently, only attempts to allocate GC alloc regions set // do_expand to true. So, we should only reach here during a // safepoint. If this assumption changes we might have to // reconsider the use of _expand_heap_after_alloc_failure. assert(SafepointSynchronize::is_at_safepoint(), "invariant"); ergo_verbose1(ErgoHeapSizing, "attempt heap expansion", ergo_format_reason("region allocation request failed") ergo_format_byte("allocation request"), word_size * HeapWordSize); if (expand(word_size * HeapWordSize)) { // Given that expand() succeeded in expanding the heap, and we // always expand the heap by an amount aligned to the heap // region size, the free list should in theory not be empty. So // it would probably be OK to use remove_head(). But the extra // check for NULL is unlikely to be a performance issue here (we // just expanded the heap!) so let's just be conservative and // use remove_head_or_null(). res = _free_list.remove_head_or_null(); } else { _expand_heap_after_alloc_failure = false; } } return res; } uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions, size_t word_size) { assert(isHumongous(word_size), "word_size should be humongous"); assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); uint first = G1_NULL_HRS_INDEX; if (num_regions == 1) { // Only one region to allocate, no need to go through the slower // path. The caller will attempt the expasion if this fails, so // let's not try to expand here too. HeapRegion* hr = new_region(word_size, false /* do_expand */); if (hr != NULL) { first = hr->hrs_index(); } else { first = G1_NULL_HRS_INDEX; } } else { // We can't allocate humongous regions while cleanupComplete() is // running, since some of the regions we find to be empty might not // yet be added to the free list and it is not straightforward to // know which list they are on so that we can remove them. Note // that we only need to do this if we need to allocate more than // one region to satisfy the current humongous allocation // request. If we are only allocating one region we use the common // region allocation code (see above). wait_while_free_regions_coming(); append_secondary_free_list_if_not_empty_with_lock(); if (free_regions() >= num_regions) { first = _hrs.find_contiguous(num_regions); if (first != G1_NULL_HRS_INDEX) { for (uint i = first; i < first + num_regions; ++i) { HeapRegion* hr = region_at(i); assert(hr->is_empty(), "sanity"); assert(is_on_master_free_list(hr), "sanity"); hr->set_pending_removal(true); } _free_list.remove_all_pending(num_regions); } } } return first; } HeapWord* G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, uint num_regions, size_t word_size) { assert(first != G1_NULL_HRS_INDEX, "pre-condition"); assert(isHumongous(word_size), "word_size should be humongous"); assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); // Index of last region in the series + 1. uint last = first + num_regions; // We need to initialize the region(s) we just discovered. This is // a bit tricky given that it can happen concurrently with // refinement threads refining cards on these regions and // potentially wanting to refine the BOT as they are scanning // those cards (this can happen shortly after a cleanup; see CR // 6991377). So we have to set up the region(s) carefully and in // a specific order. // The word size sum of all the regions we will allocate. size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; assert(word_size <= word_size_sum, "sanity"); // This will be the "starts humongous" region. HeapRegion* first_hr = region_at(first); // The header of the new object will be placed at the bottom of // the first region. HeapWord* new_obj = first_hr->bottom(); // This will be the new end of the first region in the series that // should also match the end of the last region in the seriers. HeapWord* new_end = new_obj + word_size_sum; // This will be the new top of the first region that will reflect // this allocation. HeapWord* new_top = new_obj + word_size; // First, we need to zero the header of the space that we will be // allocating. When we update top further down, some refinement // threads might try to scan the region. By zeroing the header we // ensure that any thread that will try to scan the region will // come across the zero klass word and bail out. // // NOTE: It would not have been correct to have used // CollectedHeap::fill_with_object() and make the space look like // an int array. The thread that is doing the allocation will // later update the object header to a potentially different array // type and, for a very short period of time, the klass and length // fields will be inconsistent. This could cause a refinement // thread to calculate the object size incorrectly. Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); // We will set up the first region as "starts humongous". This // will also update the BOT covering all the regions to reflect // that there is a single object that starts at the bottom of the // first region. first_hr->set_startsHumongous(new_top, new_end); // Then, if there are any, we will set up the "continues // humongous" regions. HeapRegion* hr = NULL; for (uint i = first + 1; i < last; ++i) { hr = region_at(i); hr->set_continuesHumongous(first_hr); } // If we have "continues humongous" regions (hr != NULL), then the // end of the last one should match new_end. assert(hr == NULL || hr->end() == new_end, "sanity"); // Up to this point no concurrent thread would have been able to // do any scanning on any region in this series. All the top // fields still point to bottom, so the intersection between // [bottom,top] and [card_start,card_end] will be empty. Before we // update the top fields, we'll do a storestore to make sure that // no thread sees the update to top before the zeroing of the // object header and the BOT initialization. OrderAccess::storestore(); // Now that the BOT and the object header have been initialized, // we can update top of the "starts humongous" region. assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), "new_top should be in this region"); first_hr->set_top(new_top); if (_hr_printer.is_active()) { HeapWord* bottom = first_hr->bottom(); HeapWord* end = first_hr->orig_end(); if ((first + 1) == last) { // the series has a single humongous region _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); } else { // the series has more than one humongous regions _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); } } // Now, we will update the top fields of the "continues humongous" // regions. The reason we need to do this is that, otherwise, // these regions would look empty and this will confuse parts of // G1. For example, the code that looks for a consecutive number // of empty regions will consider them empty and try to // re-allocate them. We can extend is_empty() to also include // !continuesHumongous(), but it is easier to just update the top // fields here. The way we set top for all regions (i.e., top == // end for all regions but the last one, top == new_top for the // last one) is actually used when we will free up the humongous // region in free_humongous_region(). hr = NULL; for (uint i = first + 1; i < last; ++i) { hr = region_at(i); if ((i + 1) == last) { // last continues humongous region assert(hr->bottom() < new_top && new_top <= hr->end(), "new_top should fall on this region"); hr->set_top(new_top); _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); } else { // not last one assert(new_top > hr->end(), "new_top should be above this region"); hr->set_top(hr->end()); _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); } } // If we have continues humongous regions (hr != NULL), then the // end of the last one should match new_end and its top should // match new_top. assert(hr == NULL || (hr->end() == new_end && hr->top() == new_top), "sanity"); assert(first_hr->used() == word_size * HeapWordSize, "invariant"); _summary_bytes_used += first_hr->used(); _humongous_set.add(first_hr); return new_obj; } // If could fit into free regions w/o expansion, try. // Otherwise, if can expand, do so. // Otherwise, if using ex regions might help, try with ex given back. HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); verify_region_sets_optional(); size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords); uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords); uint x_num = expansion_regions(); uint fs = _hrs.free_suffix(); uint first = humongous_obj_allocate_find_first(num_regions, word_size); if (first == G1_NULL_HRS_INDEX) { // The only thing we can do now is attempt expansion. if (fs + x_num >= num_regions) { // If the number of regions we're trying to allocate for this // object is at most the number of regions in the free suffix, // then the call to humongous_obj_allocate_find_first() above // should have succeeded and we wouldn't be here. // // We should only be trying to expand when the free suffix is // not sufficient for the object _and_ we have some expansion // room available. assert(num_regions > fs, "earlier allocation should have succeeded"); ergo_verbose1(ErgoHeapSizing, "attempt heap expansion", ergo_format_reason("humongous allocation request failed") ergo_format_byte("allocation request"), word_size * HeapWordSize); if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { // Even though the heap was expanded, it might not have // reached the desired size. So, we cannot assume that the // allocation will succeed. first = humongous_obj_allocate_find_first(num_regions, word_size); } } } HeapWord* result = NULL; if (first != G1_NULL_HRS_INDEX) { result = humongous_obj_allocate_initialize_regions(first, num_regions, word_size); assert(result != NULL, "it should always return a valid result"); // A successful humongous object allocation changes the used space // information of the old generation so we need to recalculate the // sizes and update the jstat counters here. g1mm()->update_sizes(); } verify_region_sets_optional(); return result; } HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { assert_heap_not_locked_and_not_at_safepoint(); assert(!isHumongous(word_size), "we do not allow humongous TLABs"); unsigned int dummy_gc_count_before; return attempt_allocation(word_size, &dummy_gc_count_before); } HeapWord* G1CollectedHeap::mem_allocate(size_t word_size, bool* gc_overhead_limit_was_exceeded) { assert_heap_not_locked_and_not_at_safepoint(); // Loop until the allocation is satisified, or unsatisfied after GC. for (int try_count = 1; /* we'll return */; try_count += 1) { unsigned int gc_count_before; HeapWord* result = NULL; if (!isHumongous(word_size)) { result = attempt_allocation(word_size, &gc_count_before); } else { result = attempt_allocation_humongous(word_size, &gc_count_before); } if (result != NULL) { return result; } // Create the garbage collection operation... VM_G1CollectForAllocation op(gc_count_before, word_size); // ...and get the VM thread to execute it. VMThread::execute(&op); if (op.prologue_succeeded() && op.pause_succeeded()) { // If the operation was successful we'll return the result even // if it is NULL. If the allocation attempt failed immediately // after a Full GC, it's unlikely we'll be able to allocate now. HeapWord* result = op.result(); if (result != NULL && !isHumongous(word_size)) { // Allocations that take place on VM operations do not do any // card dirtying and we have to do it here. We only have to do // this for non-humongous allocations, though. dirty_young_block(result, word_size); } return result; } else { assert(op.result() == NULL, "the result should be NULL if the VM op did not succeed"); } // Give a warning if we seem to be looping forever. if ((QueuedAllocationWarningCount > 0) && (try_count % QueuedAllocationWarningCount == 0)) { warning("G1CollectedHeap::mem_allocate retries %d times", try_count); } } ShouldNotReachHere(); return NULL; } HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, unsigned int *gc_count_before_ret) { // Make sure you read the note in attempt_allocation_humongous(). assert_heap_not_locked_and_not_at_safepoint(); assert(!isHumongous(word_size), "attempt_allocation_slow() should not " "be called for humongous allocation requests"); // We should only get here after the first-level allocation attempt // (attempt_allocation()) failed to allocate. // We will loop until a) we manage to successfully perform the // allocation or b) we successfully schedule a collection which // fails to perform the allocation. b) is the only case when we'll // return NULL. HeapWord* result = NULL; for (int try_count = 1; /* we'll return */; try_count += 1) { bool should_try_gc; unsigned int gc_count_before; { MutexLockerEx x(Heap_lock); result = _mutator_alloc_region.attempt_allocation_locked(word_size, false /* bot_updates */); if (result != NULL) { return result; } // If we reach here, attempt_allocation_locked() above failed to // allocate a new region. So the mutator alloc region should be NULL. assert(_mutator_alloc_region.get() == NULL, "only way to get here"); if (GC_locker::is_active_and_needs_gc()) { if (g1_policy()->can_expand_young_list()) { // No need for an ergo verbose message here, // can_expand_young_list() does this when it returns true. result = _mutator_alloc_region.attempt_allocation_force(word_size, false /* bot_updates */); if (result != NULL) { return result; } } should_try_gc = false; } else { // The GCLocker may not be active but the GCLocker initiated // GC may not yet have been performed (GCLocker::needs_gc() // returns true). In this case we do not try this GC and // wait until the GCLocker initiated GC is performed, and // then retry the allocation. if (GC_locker::needs_gc()) { should_try_gc = false; } else { // Read the GC count while still holding the Heap_lock. gc_count_before = total_collections(); should_try_gc = true; } } } if (should_try_gc) { bool succeeded; result = do_collection_pause(word_size, gc_count_before, &succeeded); if (result != NULL) { assert(succeeded, "only way to get back a non-NULL result"); return result; } if (succeeded) { // If we get here we successfully scheduled a collection which // failed to allocate. No point in trying to allocate // further. We'll just return NULL. MutexLockerEx x(Heap_lock); *gc_count_before_ret = total_collections(); return NULL; } } else { // The GCLocker is either active or the GCLocker initiated // GC has not yet been performed. Stall until it is and // then retry the allocation. GC_locker::stall_until_clear(); } // We can reach here if we were unsuccessul in scheduling a // collection (because another thread beat us to it) or if we were // stalled due to the GC locker. In either can we should retry the // allocation attempt in case another thread successfully // performed a collection and reclaimed enough space. We do the // first attempt (without holding the Heap_lock) here and the // follow-on attempt will be at the start of the next loop // iteration (after taking the Heap_lock). result = _mutator_alloc_region.attempt_allocation(word_size, false /* bot_updates */); if (result != NULL) { return result; } // Give a warning if we seem to be looping forever. if ((QueuedAllocationWarningCount > 0) && (try_count % QueuedAllocationWarningCount == 0)) { warning("G1CollectedHeap::attempt_allocation_slow() " "retries %d times", try_count); } } ShouldNotReachHere(); return NULL; } HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, unsigned int * gc_count_before_ret) { // The structure of this method has a lot of similarities to // attempt_allocation_slow(). The reason these two were not merged // into a single one is that such a method would require several "if // allocation is not humongous do this, otherwise do that" // conditional paths which would obscure its flow. In fact, an early // version of this code did use a unified method which was harder to // follow and, as a result, it had subtle bugs that were hard to // track down. So keeping these two methods separate allows each to // be more readable. It will be good to keep these two in sync as // much as possible. assert_heap_not_locked_and_not_at_safepoint(); assert(isHumongous(word_size), "attempt_allocation_humongous() " "should only be called for humongous allocations"); // Humongous objects can exhaust the heap quickly, so we should check if we // need to start a marking cycle at each humongous object allocation. We do // the check before we do the actual allocation. The reason for doing it // before the allocation is that we avoid having to keep track of the newly // allocated memory while we do a GC. if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", word_size)) { collect(GCCause::_g1_humongous_allocation); } // We will loop until a) we manage to successfully perform the // allocation or b) we successfully schedule a collection which // fails to perform the allocation. b) is the only case when we'll // return NULL. HeapWord* result = NULL; for (int try_count = 1; /* we'll return */; try_count += 1) { bool should_try_gc; unsigned int gc_count_before; { MutexLockerEx x(Heap_lock); // Given that humongous objects are not allocated in young // regions, we'll first try to do the allocation without doing a // collection hoping that there's enough space in the heap. result = humongous_obj_allocate(word_size); if (result != NULL) { return result; } if (GC_locker::is_active_and_needs_gc()) { should_try_gc = false; } else { // The GCLocker may not be active but the GCLocker initiated // GC may not yet have been performed (GCLocker::needs_gc() // returns true). In this case we do not try this GC and // wait until the GCLocker initiated GC is performed, and // then retry the allocation. if (GC_locker::needs_gc()) { should_try_gc = false; } else { // Read the GC count while still holding the Heap_lock. gc_count_before = total_collections(); should_try_gc = true; } } } if (should_try_gc) { // If we failed to allocate the humongous object, we should try to // do a collection pause (if we're allowed) in case it reclaims // enough space for the allocation to succeed after the pause. bool succeeded; result = do_collection_pause(word_size, gc_count_before, &succeeded); if (result != NULL) { assert(succeeded, "only way to get back a non-NULL result"); return result; } if (succeeded) { // If we get here we successfully scheduled a collection which // failed to allocate. No point in trying to allocate // further. We'll just return NULL. MutexLockerEx x(Heap_lock); *gc_count_before_ret = total_collections(); return NULL; } } else { // The GCLocker is either active or the GCLocker initiated // GC has not yet been performed. Stall until it is and // then retry the allocation. GC_locker::stall_until_clear(); } // We can reach here if we were unsuccessul in scheduling a // collection (because another thread beat us to it) or if we were // stalled due to the GC locker. In either can we should retry the // allocation attempt in case another thread successfully // performed a collection and reclaimed enough space. Give a // warning if we seem to be looping forever. if ((QueuedAllocationWarningCount > 0) && (try_count % QueuedAllocationWarningCount == 0)) { warning("G1CollectedHeap::attempt_allocation_humongous() " "retries %d times", try_count); } } ShouldNotReachHere(); return NULL; } HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, bool expect_null_mutator_alloc_region) { assert_at_safepoint(true /* should_be_vm_thread */); assert(_mutator_alloc_region.get() == NULL || !expect_null_mutator_alloc_region, "the current alloc region was unexpectedly found to be non-NULL"); if (!isHumongous(word_size)) { return _mutator_alloc_region.attempt_allocation_locked(word_size, false /* bot_updates */); } else { HeapWord* result = humongous_obj_allocate(word_size); if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { g1_policy()->set_initiate_conc_mark_if_possible(); } return result; } ShouldNotReachHere(); } class PostMCRemSetClearClosure: public HeapRegionClosure { G1CollectedHeap* _g1h; ModRefBarrierSet* _mr_bs; public: PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : _g1h(g1h), _mr_bs(mr_bs) { } bool doHeapRegion(HeapRegion* r) { if (r->continuesHumongous()) { return false; } _g1h->reset_gc_time_stamps(r); HeapRegionRemSet* hrrs = r->rem_set(); if (hrrs != NULL) hrrs->clear(); // You might think here that we could clear just the cards // corresponding to the used region. But no: if we leave a dirty card // in a region we might allocate into, then it would prevent that card // from being enqueued, and cause it to be missed. // Re: the performance cost: we shouldn't be doing full GC anyway! _mr_bs->clear(MemRegion(r->bottom(), r->end())); return false; } }; void G1CollectedHeap::clear_rsets_post_compaction() { PostMCRemSetClearClosure rs_clear(this, mr_bs()); heap_region_iterate(&rs_clear); } class RebuildRSOutOfRegionClosure: public HeapRegionClosure { G1CollectedHeap* _g1h; UpdateRSOopClosure _cl; int _worker_i; public: RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : _cl(g1->g1_rem_set(), worker_i), _worker_i(worker_i), _g1h(g1) { } bool doHeapRegion(HeapRegion* r) { if (!r->continuesHumongous()) { _cl.set_from(r); r->oop_iterate(&_cl); } return false; } }; class ParRebuildRSTask: public AbstractGangTask { G1CollectedHeap* _g1; public: ParRebuildRSTask(G1CollectedHeap* g1) : AbstractGangTask("ParRebuildRSTask"), _g1(g1) { } void work(uint worker_id) { RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, _g1->workers()->active_workers(), HeapRegion::RebuildRSClaimValue); } }; class PostCompactionPrinterClosure: public HeapRegionClosure { private: G1HRPrinter* _hr_printer; public: bool doHeapRegion(HeapRegion* hr) { assert(!hr->is_young(), "not expecting to find young regions"); // We only generate output for non-empty regions. if (!hr->is_empty()) { if (!hr->isHumongous()) { _hr_printer->post_compaction(hr, G1HRPrinter::Old); } else if (hr->startsHumongous()) { if (hr->region_num() == 1) { // single humongous region _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); } else { _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); } } else { assert(hr->continuesHumongous(), "only way to get here"); _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); } } return false; } PostCompactionPrinterClosure(G1HRPrinter* hr_printer) : _hr_printer(hr_printer) { } }; void G1CollectedHeap::print_hrs_post_compaction() { PostCompactionPrinterClosure cl(hr_printer()); heap_region_iterate(&cl); } double G1CollectedHeap::verify(bool guard, const char* msg) { double verify_time_ms = 0.0; if (guard && total_collections() >= VerifyGCStartAt) { double verify_start = os::elapsedTime(); HandleMark hm; // Discard invalid handles created during verification gclog_or_tty->print(msg); prepare_for_verify(); Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking); verify_time_ms = (os::elapsedTime() - verify_start) * 1000; } return verify_time_ms; } void G1CollectedHeap::verify_before_gc() { double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); } void G1CollectedHeap::verify_after_gc() { double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); } bool G1CollectedHeap::do_collection(bool explicit_gc, bool clear_all_soft_refs, size_t word_size) { assert_at_safepoint(true /* should_be_vm_thread */); if (GC_locker::check_active_before_gc()) { return false; } SvcGCMarker sgcm(SvcGCMarker::FULL); ResourceMark rm; print_heap_before_gc(); size_t metadata_prev_used = MetaspaceAux::used_in_bytes(); HRSPhaseSetter x(HRSPhaseFullGC); verify_region_sets_optional(); const bool do_clear_all_soft_refs = clear_all_soft_refs || collector_policy()->should_clear_all_soft_refs(); ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); { IsGCActiveMark x; // Timing assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty); TraceCollectorStats tcs(g1mm()->full_collection_counters()); TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); double start = os::elapsedTime(); g1_policy()->record_full_collection_start(); // Note: When we have a more flexible GC logging framework that // allows us to add optional attributes to a GC log record we // could consider timing and reporting how long we wait in the // following two methods. wait_while_free_regions_coming(); // If we start the compaction before the CM threads finish // scanning the root regions we might trip them over as we'll // be moving objects / updating references. So let's wait until // they are done. By telling them to abort, they should complete // early. _cm->root_regions()->abort(); _cm->root_regions()->wait_until_scan_finished(); append_secondary_free_list_if_not_empty_with_lock(); gc_prologue(true); increment_total_collections(true /* full gc */); increment_old_marking_cycles_started(); size_t g1h_prev_used = used(); assert(used() == recalculate_used(), "Should be equal"); verify_before_gc(); pre_full_gc_dump(); COMPILER2_PRESENT(DerivedPointerTable::clear()); // Disable discovery and empty the discovered lists // for the CM ref processor. ref_processor_cm()->disable_discovery(); ref_processor_cm()->abandon_partial_discovery(); ref_processor_cm()->verify_no_references_recorded(); // Abandon current iterations of concurrent marking and concurrent // refinement, if any are in progress. We have to do this before // wait_until_scan_finished() below. concurrent_mark()->abort(); // Make sure we'll choose a new allocation region afterwards. release_mutator_alloc_region(); abandon_gc_alloc_regions(); g1_rem_set()->cleanupHRRS(); // We should call this after we retire any currently active alloc // regions so that all the ALLOC / RETIRE events are generated // before the start GC event. _hr_printer.start_gc(true /* full */, (size_t) total_collections()); // We may have added regions to the current incremental collection // set between the last GC or pause and now. We need to clear the // incremental collection set and then start rebuilding it afresh // after this full GC. abandon_collection_set(g1_policy()->inc_cset_head()); g1_policy()->clear_incremental_cset(); g1_policy()->stop_incremental_cset_building(); tear_down_region_sets(false /* free_list_only */); g1_policy()->set_gcs_are_young(true); // See the comments in g1CollectedHeap.hpp and // G1CollectedHeap::ref_processing_init() about // how reference processing currently works in G1. // Temporarily make discovery by the STW ref processor single threaded (non-MT). ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); // Temporarily clear the STW ref processor's _is_alive_non_header field. ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); ref_processor_stw()->setup_policy(do_clear_all_soft_refs); // Do collection work { HandleMark hm; // Discard invalid handles created during gc G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); } assert(free_regions() == 0, "we should not have added any free regions"); rebuild_region_sets(false /* free_list_only */); // Enqueue any discovered reference objects that have // not been removed from the discovered lists. ref_processor_stw()->enqueue_discovered_references(); COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); MemoryService::track_memory_usage(); verify_after_gc(); assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); ref_processor_stw()->verify_no_references_recorded(); // Delete metaspaces for unloaded class loaders and clean up loader_data graph ClassLoaderDataGraph::purge(); // Note: since we've just done a full GC, concurrent // marking is no longer active. Therefore we need not // re-enable reference discovery for the CM ref processor. // That will be done at the start of the next marking cycle. assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); ref_processor_cm()->verify_no_references_recorded(); reset_gc_time_stamp(); // Since everything potentially moved, we will clear all remembered // sets, and clear all cards. Later we will rebuild remebered // sets. We will also reset the GC time stamps of the regions. clear_rsets_post_compaction(); check_gc_time_stamps(); // Resize the heap if necessary. resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); if (_hr_printer.is_active()) { // We should do this after we potentially resize the heap so // that all the COMMIT / UNCOMMIT events are generated before // the end GC event. print_hrs_post_compaction(); _hr_printer.end_gc(true /* full */, (size_t) total_collections()); } if (_cg1r->use_cache()) { _cg1r->clear_and_record_card_counts(); _cg1r->clear_hot_cache(); } // Rebuild remembered sets of all regions. if (G1CollectedHeap::use_parallel_gc_threads()) { uint n_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), workers()->active_workers(), Threads::number_of_non_daemon_threads()); assert(UseDynamicNumberOfGCThreads || n_workers == workers()->total_workers(), "If not dynamic should be using all the workers"); workers()->set_active_workers(n_workers); // Set parallel threads in the heap (_n_par_threads) only // before a parallel phase and always reset it to 0 after // the phase so that the number of parallel threads does // no get carried forward to a serial phase where there // may be code that is "possibly_parallel". set_par_threads(n_workers); ParRebuildRSTask rebuild_rs_task(this); assert(check_heap_region_claim_values( HeapRegion::InitialClaimValue), "sanity check"); assert(UseDynamicNumberOfGCThreads || workers()->active_workers() == workers()->total_workers(), "Unless dynamic should use total workers"); // Use the most recent number of active workers assert(workers()->active_workers() > 0, "Active workers not properly set"); set_par_threads(workers()->active_workers()); workers()->run_task(&rebuild_rs_task); set_par_threads(0); assert(check_heap_region_claim_values( HeapRegion::RebuildRSClaimValue), "sanity check"); reset_heap_region_claim_values(); } else { RebuildRSOutOfRegionClosure rebuild_rs(this); heap_region_iterate(&rebuild_rs); } if (G1Log::fine()) { print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity()); } if (true) { // FIXME MetaspaceGC::compute_new_size(); } // Start a new incremental collection set for the next pause assert(g1_policy()->collection_set() == NULL, "must be"); g1_policy()->start_incremental_cset_building(); // Clear the _cset_fast_test bitmap in anticipation of adding // regions to the incremental collection set for the next // evacuation pause. clear_cset_fast_test(); init_mutator_alloc_region(); double end = os::elapsedTime(); g1_policy()->record_full_collection_end(); #ifdef TRACESPINNING ParallelTaskTerminator::print_termination_counts(); #endif gc_epilogue(true); // Discard all rset updates JavaThread::dirty_card_queue_set().abandon_logs(); assert(!G1DeferredRSUpdate || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); _young_list->reset_sampled_info(); // At this point there should be no regions in the // entire heap tagged as young. assert( check_young_list_empty(true /* check_heap */), "young list should be empty at this point"); // Update the number of full collections that have been completed. increment_old_marking_cycles_completed(false /* concurrent */); _hrs.verify_optional(); verify_region_sets_optional(); print_heap_after_gc(); // We must call G1MonitoringSupport::update_sizes() in the same scoping level // as an active TraceMemoryManagerStats object (i.e. before the destructor for the // TraceMemoryManagerStats is called) so that the G1 memory pools are updated // before any GC notifications are raised. g1mm()->update_sizes(); } post_full_gc_dump(); return true; } void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { // do_collection() will return whether it succeeded in performing // the GC. Currently, there is no facility on the // do_full_collection() API to notify the caller than the collection // did not succeed (e.g., because it was locked out by the GC // locker). So, right now, we'll ignore the return value. bool dummy = do_collection(true, /* explicit_gc */ clear_all_soft_refs, 0 /* word_size */); } // This code is mostly copied from TenuredGeneration. void G1CollectedHeap:: resize_if_necessary_after_full_collection(size_t word_size) { assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); // Include the current allocation, if any, and bytes that will be // pre-allocated to support collections, as "used". const size_t used_after_gc = used(); const size_t capacity_after_gc = capacity(); const size_t free_after_gc = capacity_after_gc - used_after_gc; // This is enforced in arguments.cpp. assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "otherwise the code below doesn't make sense"); // We don't have floating point command-line arguments const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; const double maximum_used_percentage = 1.0 - minimum_free_percentage; const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; const double minimum_used_percentage = 1.0 - maximum_free_percentage; const size_t min_heap_size = collector_policy()->min_heap_byte_size(); const size_t max_heap_size = collector_policy()->max_heap_byte_size(); // We have to be careful here as these two calculations can overflow // 32-bit size_t's. double used_after_gc_d = (double) used_after_gc; double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; // Let's make sure that they are both under the max heap size, which // by default will make them fit into a size_t. double desired_capacity_upper_bound = (double) max_heap_size; minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, desired_capacity_upper_bound); maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, desired_capacity_upper_bound); // We can now safely turn them into size_t's. size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; // This assert only makes sense here, before we adjust them // with respect to the min and max heap size. assert(minimum_desired_capacity <= maximum_desired_capacity, err_msg("minimum_desired_capacity = "SIZE_FORMAT", " "maximum_desired_capacity = "SIZE_FORMAT, minimum_desired_capacity, maximum_desired_capacity)); // Should not be greater than the heap max size. No need to adjust // it with respect to the heap min size as it's a lower bound (i.e., // we'll try to make the capacity larger than it, not smaller). minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); // Should not be less than the heap min size. No need to adjust it // with respect to the heap max size as it's an upper bound (i.e., // we'll try to make the capacity smaller than it, not greater). maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); if (capacity_after_gc < minimum_desired_capacity) { // Don't expand unless it's significant size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; ergo_verbose4(ErgoHeapSizing, "attempt heap expansion", ergo_format_reason("capacity lower than " "min desired capacity after Full GC") ergo_format_byte("capacity") ergo_format_byte("occupancy") ergo_format_byte_perc("min desired capacity"), capacity_after_gc, used_after_gc, minimum_desired_capacity, (double) MinHeapFreeRatio); expand(expand_bytes); // No expansion, now see if we want to shrink } else if (capacity_after_gc > maximum_desired_capacity) { // Capacity too large, compute shrinking size size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; ergo_verbose4(ErgoHeapSizing, "attempt heap shrinking", ergo_format_reason("capacity higher than " "max desired capacity after Full GC") ergo_format_byte("capacity") ergo_format_byte("occupancy") ergo_format_byte_perc("max desired capacity"), capacity_after_gc, used_after_gc, maximum_desired_capacity, (double) MaxHeapFreeRatio); shrink(shrink_bytes); } } HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size, bool* succeeded) { assert_at_safepoint(true /* should_be_vm_thread */); *succeeded = true; // Let's attempt the allocation first. HeapWord* result = attempt_allocation_at_safepoint(word_size, false /* expect_null_mutator_alloc_region */); if (result != NULL) { assert(*succeeded, "sanity"); return result; } // In a G1 heap, we're supposed to keep allocation from failing by // incremental pauses. Therefore, at least for now, we'll favor // expansion over collection. (This might change in the future if we can // do something smarter than full collection to satisfy a failed alloc.) result = expand_and_allocate(word_size); if (result != NULL) { assert(*succeeded, "sanity"); return result; } // Expansion didn't work, we'll try to do a Full GC. bool gc_succeeded = do_collection(false, /* explicit_gc */ false, /* clear_all_soft_refs */ word_size); if (!gc_succeeded) { *succeeded = false; return NULL; } // Retry the allocation result = attempt_allocation_at_safepoint(word_size, true /* expect_null_mutator_alloc_region */); if (result != NULL) { assert(*succeeded, "sanity"); return result; } // Then, try a Full GC that will collect all soft references. gc_succeeded = do_collection(false, /* explicit_gc */ true, /* clear_all_soft_refs */ word_size); if (!gc_succeeded) { *succeeded = false; return NULL; } // Retry the allocation once more result = attempt_allocation_at_safepoint(word_size, true /* expect_null_mutator_alloc_region */); if (result != NULL) { assert(*succeeded, "sanity"); return result; } assert(!collector_policy()->should_clear_all_soft_refs(), "Flag should have been handled and cleared prior to this point"); // What else? We might try synchronous finalization later. If the total // space available is large enough for the allocation, then a more // complete compaction phase than we've tried so far might be // appropriate. assert(*succeeded, "sanity"); return NULL; } // Attempting to expand the heap sufficiently // to support an allocation of the given "word_size". If // successful, perform the allocation and return the address of the // allocated block, or else "NULL". HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { assert_at_safepoint(true /* should_be_vm_thread */); verify_region_sets_optional(); size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); ergo_verbose1(ErgoHeapSizing, "attempt heap expansion", ergo_format_reason("allocation request failed") ergo_format_byte("allocation request"), word_size * HeapWordSize); if (expand(expand_bytes)) { _hrs.verify_optional(); verify_region_sets_optional(); return attempt_allocation_at_safepoint(word_size, false /* expect_null_mutator_alloc_region */); } return NULL; } void G1CollectedHeap::update_committed_space(HeapWord* old_end, HeapWord* new_end) { assert(old_end != new_end, "don't call this otherwise"); assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); // Update the committed mem region. _g1_committed.set_end(new_end); // Tell the card table about the update. Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); // Tell the BOT about the update. _bot_shared->resize(_g1_committed.word_size()); } bool G1CollectedHeap::expand(size_t expand_bytes) { size_t old_mem_size = _g1_storage.committed_size(); size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); aligned_expand_bytes = align_size_up(aligned_expand_bytes, HeapRegion::GrainBytes); ergo_verbose2(ErgoHeapSizing, "expand the heap", ergo_format_byte("requested expansion amount") ergo_format_byte("attempted expansion amount"), expand_bytes, aligned_expand_bytes); // First commit the memory. HeapWord* old_end = (HeapWord*) _g1_storage.high(); bool successful = _g1_storage.expand_by(aligned_expand_bytes); if (successful) { // Then propagate this update to the necessary data structures. HeapWord* new_end = (HeapWord*) _g1_storage.high(); update_committed_space(old_end, new_end); FreeRegionList expansion_list("Local Expansion List"); MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); assert(mr.start() == old_end, "post-condition"); // mr might be a smaller region than what was requested if // expand_by() was unable to allocate the HeapRegion instances assert(mr.end() <= new_end, "post-condition"); size_t actual_expand_bytes = mr.byte_size(); assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), "post-condition"); if (actual_expand_bytes < aligned_expand_bytes) { // We could not expand _hrs to the desired size. In this case we // need to shrink the committed space accordingly. assert(mr.end() < new_end, "invariant"); size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; // First uncommit the memory. _g1_storage.shrink_by(diff_bytes); // Then propagate this update to the necessary data structures. update_committed_space(new_end, mr.end()); } _free_list.add_as_tail(&expansion_list); if (_hr_printer.is_active()) { HeapWord* curr = mr.start(); while (curr < mr.end()) { HeapWord* curr_end = curr + HeapRegion::GrainWords; _hr_printer.commit(curr, curr_end); curr = curr_end; } assert(curr == mr.end(), "post-condition"); } g1_policy()->record_new_heap_size(n_regions()); } else { ergo_verbose0(ErgoHeapSizing, "did not expand the heap", ergo_format_reason("heap expansion operation failed")); // The expansion of the virtual storage space was unsuccessful. // Let's see if it was because we ran out of swap. if (G1ExitOnExpansionFailure && _g1_storage.uncommitted_size() >= aligned_expand_bytes) { // We had head room... vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion"); } } return successful; } void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { size_t old_mem_size = _g1_storage.committed_size(); size_t aligned_shrink_bytes = ReservedSpace::page_align_size_down(shrink_bytes); aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, HeapRegion::GrainBytes); uint num_regions_deleted = 0; MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted); HeapWord* old_end = (HeapWord*) _g1_storage.high(); assert(mr.end() == old_end, "post-condition"); ergo_verbose3(ErgoHeapSizing, "shrink the heap", ergo_format_byte("requested shrinking amount") ergo_format_byte("aligned shrinking amount") ergo_format_byte("attempted shrinking amount"), shrink_bytes, aligned_shrink_bytes, mr.byte_size()); if (mr.byte_size() > 0) { if (_hr_printer.is_active()) { HeapWord* curr = mr.end(); while (curr > mr.start()) { HeapWord* curr_end = curr; curr -= HeapRegion::GrainWords; _hr_printer.uncommit(curr, curr_end); } assert(curr == mr.start(), "post-condition"); } _g1_storage.shrink_by(mr.byte_size()); HeapWord* new_end = (HeapWord*) _g1_storage.high(); assert(mr.start() == new_end, "post-condition"); _expansion_regions += num_regions_deleted; update_committed_space(old_end, new_end); HeapRegionRemSet::shrink_heap(n_regions()); g1_policy()->record_new_heap_size(n_regions()); } else { ergo_verbose0(ErgoHeapSizing, "did not shrink the heap", ergo_format_reason("heap shrinking operation failed")); } } void G1CollectedHeap::shrink(size_t shrink_bytes) { verify_region_sets_optional(); // We should only reach here at the end of a Full GC which means we // should not not be holding to any GC alloc regions. The method // below will make sure of that and do any remaining clean up. abandon_gc_alloc_regions(); // Instead of tearing down / rebuilding the free lists here, we // could instead use the remove_all_pending() method on free_list to // remove only the ones that we need to remove. tear_down_region_sets(true /* free_list_only */); shrink_helper(shrink_bytes); rebuild_region_sets(true /* free_list_only */); _hrs.verify_optional(); verify_region_sets_optional(); } // Public methods. #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away #pragma warning( disable:4355 ) // 'this' : used in base member initializer list #endif // _MSC_VER G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : SharedHeap(policy_), _g1_policy(policy_), _dirty_card_queue_set(false), _into_cset_dirty_card_queue_set(false), _is_alive_closure_cm(this), _is_alive_closure_stw(this), _ref_processor_cm(NULL), _ref_processor_stw(NULL), _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), _bot_shared(NULL), _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL), _evac_failure_scan_stack(NULL) , _mark_in_progress(false), _cg1r(NULL), _summary_bytes_used(0), _g1mm(NULL), _refine_cte_cl(NULL), _full_collection(false), _free_list("Master Free List"), _secondary_free_list("Secondary Free List"), _old_set("Old Set"), _humongous_set("Master Humongous Set"), _free_regions_coming(false), _young_list(new YoungList(this)), _gc_time_stamp(0), _retained_old_gc_alloc_region(NULL), _survivor_plab_stats(YoungPLABSize, PLABWeight), _old_plab_stats(OldPLABSize, PLABWeight), _expand_heap_after_alloc_failure(true), _surviving_young_words(NULL), _old_marking_cycles_started(0), _old_marking_cycles_completed(0), _in_cset_fast_test(NULL), _in_cset_fast_test_base(NULL), _dirty_cards_region_list(NULL), _worker_cset_start_region(NULL), _worker_cset_start_region_time_stamp(NULL) { _g1h = this; // To catch bugs. if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { vm_exit_during_initialization("Failed necessary allocation."); } _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; int n_queues = MAX2((int)ParallelGCThreads, 1); _task_queues = new RefToScanQueueSet(n_queues); int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); assert(n_rem_sets > 0, "Invariant."); HeapRegionRemSetIterator** iter_arr = NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC); for (int i = 0; i < n_queues; i++) { iter_arr[i] = new HeapRegionRemSetIterator(); } _rem_set_iterator = iter_arr; _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); for (int i = 0; i < n_queues; i++) { RefToScanQueue* q = new RefToScanQueue(); q->initialize(); _task_queues->register_queue(i, q); } clear_cset_start_regions(); // Initialize the G1EvacuationFailureALot counters and flags. NOT_PRODUCT(reset_evacuation_should_fail();) guarantee(_task_queues != NULL, "task_queues allocation failure."); } jint G1CollectedHeap::initialize() { CollectedHeap::pre_initialize(); os::enable_vtime(); G1Log::init(); // Necessary to satisfy locking discipline assertions. MutexLocker x(Heap_lock); // We have to initialize the printer before committing the heap, as // it will be used then. _hr_printer.set_active(G1PrintHeapRegions); // While there are no constraints in the GC code that HeapWordSize // be any particular value, there are multiple other areas in the // system which believe this to be true (e.g. oop->object_size in some // cases incorrectly returns the size in wordSize units rather than // HeapWordSize). guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); size_t init_byte_size = collector_policy()->initial_heap_byte_size(); size_t max_byte_size = collector_policy()->max_heap_byte_size(); // Ensure that the sizes are properly aligned. Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); _cg1r = new ConcurrentG1Refine(); // Reserve the maximum. // When compressed oops are enabled, the preferred heap base // is calculated by subtracting the requested size from the // 32Gb boundary and using the result as the base address for // heap reservation. If the requested size is not aligned to // HeapRegion::GrainBytes (i.e. the alignment that is passed // into the ReservedHeapSpace constructor) then the actual // base of the reserved heap may end up differing from the // address that was requested (i.e. the preferred heap base). // If this happens then we could end up using a non-optimal // compressed oops mode. // Since max_byte_size is aligned to the size of a heap region (checked // above). Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, HeapRegion::GrainBytes); // It is important to do this in a way such that concurrent readers can't // temporarily think somethings in the heap. (I've actually seen this // happen in asserts: DLD.) _reserved.set_word_size(0); _reserved.set_start((HeapWord*)heap_rs.base()); _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); // Create the gen rem set (and barrier set) for the entire reserved region. _rem_set = collector_policy()->create_rem_set(_reserved, 2); set_barrier_set(rem_set()->bs()); if (barrier_set()->is_a(BarrierSet::ModRef)) { _mr_bs = (ModRefBarrierSet*)_barrier_set; } else { vm_exit_during_initialization("G1 requires a mod ref bs."); return JNI_ENOMEM; } // Also create a G1 rem set. if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); } else { vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); return JNI_ENOMEM; } // Carve out the G1 part of the heap. ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), g1_rs.size()/HeapWordSize); _g1_storage.initialize(g1_rs, 0); _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); _hrs.initialize((HeapWord*) _g1_reserved.start(), (HeapWord*) _g1_reserved.end(), _expansion_regions); // 6843694 - ensure that the maximum region index can fit // in the remembered set structures. const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, "too many cards per region"); HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); _bot_shared = new G1BlockOffsetSharedArray(_reserved, heap_word_size(init_byte_size)); _g1h = this; _in_cset_fast_test_length = max_regions(); _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC); // We're biasing _in_cset_fast_test to avoid subtracting the // beginning of the heap every time we want to index; basically // it's the same with what we do with the card table. _in_cset_fast_test = _in_cset_fast_test_base - ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); // Clear the _cset_fast_test bitmap in anticipation of adding // regions to the incremental collection set for the first // evacuation pause. clear_cset_fast_test(); // Create the ConcurrentMark data structure and thread. // (Must do this late, so that "max_regions" is defined.) _cm = new ConcurrentMark(this, heap_rs); if (_cm == NULL || !_cm->completed_initialization()) { vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); return JNI_ENOMEM; } _cmThread = _cm->cmThread(); // Initialize the from_card cache structure of HeapRegionRemSet. HeapRegionRemSet::init_heap(max_regions()); // Now expand into the initial heap size. if (!expand(init_byte_size)) { vm_shutdown_during_initialization("Failed to allocate initial heap."); return JNI_ENOMEM; } // Perform any initialization actions delegated to the policy. g1_policy()->init(); _refine_cte_cl = new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), g1_rem_set(), concurrent_g1_refine()); JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, SATB_Q_FL_lock, G1SATBProcessCompletedThreshold, Shared_SATB_Q_lock); JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, DirtyCardQ_FL_lock, concurrent_g1_refine()->yellow_zone(), concurrent_g1_refine()->red_zone(), Shared_DirtyCardQ_lock); if (G1DeferredRSUpdate) { dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, DirtyCardQ_FL_lock, -1, // never trigger processing -1, // no limit on length Shared_DirtyCardQ_lock, &JavaThread::dirty_card_queue_set()); } // Initialize the card queue set used to hold cards containing // references into the collection set. _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, DirtyCardQ_FL_lock, -1, // never trigger processing -1, // no limit on length Shared_DirtyCardQ_lock, &JavaThread::dirty_card_queue_set()); // In case we're keeping closure specialization stats, initialize those // counts and that mechanism. SpecializationStats::clear(); // Do later initialization work for concurrent refinement. _cg1r->init(); // Here we allocate the dummy full region that is required by the // G1AllocRegion class. If we don't pass an address in the reserved // space here, lots of asserts fire. HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, _g1_reserved.start()); // We'll re-use the same region whether the alloc region will // require BOT updates or not and, if it doesn't, then a non-young // region will complain that it cannot support allocations without // BOT updates. So we'll tag the dummy region as young to avoid that. dummy_region->set_young(); // Make sure it's full. dummy_region->set_top(dummy_region->end()); G1AllocRegion::setup(this, dummy_region); init_mutator_alloc_region(); // Do create of the monitoring and management support so that // values in the heap have been properly initialized. _g1mm = new G1MonitoringSupport(this); return JNI_OK; } void G1CollectedHeap::ref_processing_init() { // Reference processing in G1 currently works as follows: // // * There are two reference processor instances. One is // used to record and process discovered references // during concurrent marking; the other is used to // record and process references during STW pauses // (both full and incremental). // * Both ref processors need to 'span' the entire heap as // the regions in the collection set may be dotted around. // // * For the concurrent marking ref processor: // * Reference discovery is enabled at initial marking. // * Reference discovery is disabled and the discovered // references processed etc during remarking. // * Reference discovery is MT (see below). // * Reference discovery requires a barrier (see below). // * Reference processing may or may not be MT // (depending on the value of ParallelRefProcEnabled // and ParallelGCThreads). // * A full GC disables reference discovery by the CM // ref processor and abandons any entries on it's // discovered lists. // // * For the STW processor: // * Non MT discovery is enabled at the start of a full GC. // * Processing and enqueueing during a full GC is non-MT. // * During a full GC, references are processed after marking. // // * Discovery (may or may not be MT) is enabled at the start // of an incremental evacuation pause. // * References are processed near the end of a STW evacuation pause. // * For both types of GC: // * Discovery is atomic - i.e. not concurrent. // * Reference discovery will not need a barrier. SharedHeap::ref_processing_init(); MemRegion mr = reserved_region(); // Concurrent Mark ref processor _ref_processor_cm = new ReferenceProcessor(mr, // span ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing (int) ParallelGCThreads, // degree of mt processing (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery (int) MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery false, // Reference discovery is not atomic &_is_alive_closure_cm, // is alive closure // (for efficiency/performance) true); // Setting next fields of discovered // lists requires a barrier. // STW ref processor _ref_processor_stw = new ReferenceProcessor(mr, // span ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing MAX2((int)ParallelGCThreads, 1), // degree of mt processing (ParallelGCThreads > 1), // mt discovery MAX2((int)ParallelGCThreads, 1), // degree of mt discovery true, // Reference discovery is atomic &_is_alive_closure_stw, // is alive closure // (for efficiency/performance) false); // Setting next fields of discovered // lists requires a barrier. } size_t G1CollectedHeap::capacity() const { return _g1_committed.byte_size(); } void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { assert(!hr->continuesHumongous(), "pre-condition"); hr->reset_gc_time_stamp(); if (hr->startsHumongous()) { uint first_index = hr->hrs_index() + 1; uint last_index = hr->last_hc_index(); for (uint i = first_index; i < last_index; i += 1) { HeapRegion* chr = region_at(i); assert(chr->continuesHumongous(), "sanity"); chr->reset_gc_time_stamp(); } } } #ifndef PRODUCT class CheckGCTimeStampsHRClosure : public HeapRegionClosure { private: unsigned _gc_time_stamp; bool _failures; public: CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : _gc_time_stamp(gc_time_stamp), _failures(false) { } virtual bool doHeapRegion(HeapRegion* hr) { unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); if (_gc_time_stamp != region_gc_time_stamp) { gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " "expected %d", HR_FORMAT_PARAMS(hr), region_gc_time_stamp, _gc_time_stamp); _failures = true; } return false; } bool failures() { return _failures; } }; void G1CollectedHeap::check_gc_time_stamps() { CheckGCTimeStampsHRClosure cl(_gc_time_stamp); heap_region_iterate(&cl); guarantee(!cl.failures(), "all GC time stamps should have been reset"); } #endif // PRODUCT void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, DirtyCardQueue* into_cset_dcq, bool concurrent, int worker_i) { // Clean cards in the hot card cache concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq); DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); int n_completed_buffers = 0; while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { n_completed_buffers++; } g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); dcqs.clear_n_completed_buffers(); assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); } // Computes the sum of the storage used by the various regions. size_t G1CollectedHeap::used() const { assert(Heap_lock->owner() != NULL, "Should be owned on this thread's behalf."); size_t result = _summary_bytes_used; // Read only once in case it is set to NULL concurrently HeapRegion* hr = _mutator_alloc_region.get(); if (hr != NULL) result += hr->used(); return result; } size_t G1CollectedHeap::used_unlocked() const { size_t result = _summary_bytes_used; return result; } class SumUsedClosure: public HeapRegionClosure { size_t _used; public: SumUsedClosure() : _used(0) {} bool doHeapRegion(HeapRegion* r) { if (!r->continuesHumongous()) { _used += r->used(); } return false; } size_t result() { return _used; } }; size_t G1CollectedHeap::recalculate_used() const { SumUsedClosure blk; heap_region_iterate(&blk); return blk.result(); } size_t G1CollectedHeap::unsafe_max_alloc() { if (free_regions() > 0) return HeapRegion::GrainBytes; // otherwise, is there space in the current allocation region? // We need to store the current allocation region in a local variable // here. The problem is that this method doesn't take any locks and // there may be other threads which overwrite the current allocation // region field. attempt_allocation(), for example, sets it to NULL // and this can happen *after* the NULL check here but before the call // to free(), resulting in a SIGSEGV. Note that this doesn't appear // to be a problem in the optimized build, since the two loads of the // current allocation region field are optimized away. HeapRegion* hr = _mutator_alloc_region.get(); if (hr == NULL) { return 0; } return hr->free(); } bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { switch (cause) { case GCCause::_gc_locker: return GCLockerInvokesConcurrent; case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; case GCCause::_g1_humongous_allocation: return true; default: return false; } } #ifndef PRODUCT void G1CollectedHeap::allocate_dummy_regions() { // Let's fill up most of the region size_t word_size = HeapRegion::GrainWords - 1024; // And as a result the region we'll allocate will be humongous. guarantee(isHumongous(word_size), "sanity"); for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { // Let's use the existing mechanism for the allocation HeapWord* dummy_obj = humongous_obj_allocate(word_size); if (dummy_obj != NULL) { MemRegion mr(dummy_obj, word_size); CollectedHeap::fill_with_object(mr); } else { // If we can't allocate once, we probably cannot allocate // again. Let's get out of the loop. break; } } } #endif // !PRODUCT void G1CollectedHeap::increment_old_marking_cycles_started() { assert(_old_marking_cycles_started == _old_marking_cycles_completed || _old_marking_cycles_started == _old_marking_cycles_completed + 1, err_msg("Wrong marking cycle count (started: %d, completed: %d)", _old_marking_cycles_started, _old_marking_cycles_completed)); _old_marking_cycles_started++; } void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); // We assume that if concurrent == true, then the caller is a // concurrent thread that was joined the Suspendible Thread // Set. If there's ever a cheap way to check this, we should add an // assert here. // Given that this method is called at the end of a Full GC or of a // concurrent cycle, and those can be nested (i.e., a Full GC can // interrupt a concurrent cycle), the number of full collections // completed should be either one (in the case where there was no // nesting) or two (when a Full GC interrupted a concurrent cycle) // behind the number of full collections started. // This is the case for the inner caller, i.e. a Full GC. assert(concurrent || (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || (_old_marking_cycles_started == _old_marking_cycles_completed + 2), err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " "is inconsistent with _old_marking_cycles_completed = %u", _old_marking_cycles_started, _old_marking_cycles_completed)); // This is the case for the outer caller, i.e. the concurrent cycle. assert(!concurrent || (_old_marking_cycles_started == _old_marking_cycles_completed + 1), err_msg("for outer caller (concurrent cycle): " "_old_marking_cycles_started = %u " "is inconsistent with _old_marking_cycles_completed = %u", _old_marking_cycles_started, _old_marking_cycles_completed)); _old_marking_cycles_completed += 1; // We need to clear the "in_progress" flag in the CM thread before // we wake up any waiters (especially when ExplicitInvokesConcurrent // is set) so that if a waiter requests another System.gc() it doesn't // incorrectly see that a marking cyle is still in progress. if (concurrent) { _cmThread->clear_in_progress(); } // This notify_all() will ensure that a thread that called // System.gc() with (with ExplicitGCInvokesConcurrent set or not) // and it's waiting for a full GC to finish will be woken up. It is // waiting in VM_G1IncCollectionPause::doit_epilogue(). FullGCCount_lock->notify_all(); } void G1CollectedHeap::collect(GCCause::Cause cause) { assert_heap_not_locked(); unsigned int gc_count_before; unsigned int old_marking_count_before; bool retry_gc; do { retry_gc = false; { MutexLocker ml(Heap_lock); // Read the GC count while holding the Heap_lock gc_count_before = total_collections(); old_marking_count_before = _old_marking_cycles_started; } if (should_do_concurrent_full_gc(cause)) { // Schedule an initial-mark evacuation pause that will start a // concurrent cycle. We're setting word_size to 0 which means that // we are not requesting a post-GC allocation. VM_G1IncCollectionPause op(gc_count_before, 0, /* word_size */ true, /* should_initiate_conc_mark */ g1_policy()->max_pause_time_ms(), cause); VMThread::execute(&op); if (!op.pause_succeeded()) { if (old_marking_count_before == _old_marking_cycles_started) { retry_gc = op.should_retry_gc(); } else { // A Full GC happened while we were trying to schedule the // initial-mark GC. No point in starting a new cycle given // that the whole heap was collected anyway. } if (retry_gc) { if (GC_locker::is_active_and_needs_gc()) { GC_locker::stall_until_clear(); } } } } else { if (cause == GCCause::_gc_locker DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { // Schedule a standard evacuation pause. We're setting word_size // to 0 which means that we are not requesting a post-GC allocation. VM_G1IncCollectionPause op(gc_count_before, 0, /* word_size */ false, /* should_initiate_conc_mark */ g1_policy()->max_pause_time_ms(), cause); VMThread::execute(&op); } else { // Schedule a Full GC. VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); VMThread::execute(&op); } } } while (retry_gc); } bool G1CollectedHeap::is_in(const void* p) const { if (_g1_committed.contains(p)) { // Given that we know that p is in the committed space, // heap_region_containing_raw() should successfully // return the containing region. HeapRegion* hr = heap_region_containing_raw(p); return hr->is_in(p); } else { return false; } } // Iteration functions. // Iterates an OopClosure over all ref-containing fields of objects // within a HeapRegion. class IterateOopClosureRegionClosure: public HeapRegionClosure { MemRegion _mr; ExtendedOopClosure* _cl; public: IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) : _mr(mr), _cl(cl) {} bool doHeapRegion(HeapRegion* r) { if (!r->continuesHumongous()) { r->oop_iterate(_cl); } return false; } }; void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { IterateOopClosureRegionClosure blk(_g1_committed, cl); heap_region_iterate(&blk); } void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { IterateOopClosureRegionClosure blk(mr, cl); heap_region_iterate(&blk); } // Iterates an ObjectClosure over all objects within a HeapRegion. class IterateObjectClosureRegionClosure: public HeapRegionClosure { ObjectClosure* _cl; public: IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} bool doHeapRegion(HeapRegion* r) { if (! r->continuesHumongous()) { r->object_iterate(_cl); } return false; } }; void G1CollectedHeap::object_iterate(ObjectClosure* cl) { IterateObjectClosureRegionClosure blk(cl); heap_region_iterate(&blk); } void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { // FIXME: is this right? guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); } // Calls a SpaceClosure on a HeapRegion. class SpaceClosureRegionClosure: public HeapRegionClosure { SpaceClosure* _cl; public: SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} bool doHeapRegion(HeapRegion* r) { _cl->do_space(r); return false; } }; void G1CollectedHeap::space_iterate(SpaceClosure* cl) { SpaceClosureRegionClosure blk(cl); heap_region_iterate(&blk); } void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { _hrs.iterate(cl); } void G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, uint worker_id, uint no_of_par_workers, jint claim_value) { const uint regions = n_regions(); const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1); assert(UseDynamicNumberOfGCThreads || no_of_par_workers == workers()->total_workers(), "Non dynamic should use fixed number of workers"); // try to spread out the starting points of the workers const HeapRegion* start_hr = start_region_for_worker(worker_id, no_of_par_workers); const uint start_index = start_hr->hrs_index(); // each worker will actually look at all regions for (uint count = 0; count < regions; ++count) { const uint index = (start_index + count) % regions; assert(0 <= index && index < regions, "sanity"); HeapRegion* r = region_at(index); // we'll ignore "continues humongous" regions (we'll process them // when we come across their corresponding "start humongous" // region) and regions already claimed if (r->claim_value() == claim_value || r->continuesHumongous()) { continue; } // OK, try to claim it if (r->claimHeapRegion(claim_value)) { // success! assert(!r->continuesHumongous(), "sanity"); if (r->startsHumongous()) { // If the region is "starts humongous" we'll iterate over its // "continues humongous" first; in fact we'll do them // first. The order is important. In on case, calling the // closure on the "starts humongous" region might de-allocate // and clear all its "continues humongous" regions and, as a // result, we might end up processing them twice. So, we'll do // them first (notice: most closures will ignore them anyway) and // then we'll do the "starts humongous" region. for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { HeapRegion* chr = region_at(ch_index); // if the region has already been claimed or it's not // "continues humongous" we're done if (chr->claim_value() == claim_value || !chr->continuesHumongous()) { break; } // Noone should have claimed it directly. We can given // that we claimed its "starts humongous" region. assert(chr->claim_value() != claim_value, "sanity"); assert(chr->humongous_start_region() == r, "sanity"); if (chr->claimHeapRegion(claim_value)) { // we should always be able to claim it; noone else should // be trying to claim this region bool res2 = cl->doHeapRegion(chr); assert(!res2, "Should not abort"); // Right now, this holds (i.e., no closure that actually // does something with "continues humongous" regions // clears them). We might have to weaken it in the future, // but let's leave these two asserts here for extra safety. assert(chr->continuesHumongous(), "should still be the case"); assert(chr->humongous_start_region() == r, "sanity"); } else { guarantee(false, "we should not reach here"); } } } assert(!r->continuesHumongous(), "sanity"); bool res = cl->doHeapRegion(r); assert(!res, "Should not abort"); } } } class ResetClaimValuesClosure: public HeapRegionClosure { public: bool doHeapRegion(HeapRegion* r) { r->set_claim_value(HeapRegion::InitialClaimValue); return false; } }; void G1CollectedHeap::reset_heap_region_claim_values() { ResetClaimValuesClosure blk; heap_region_iterate(&blk); } void G1CollectedHeap::reset_cset_heap_region_claim_values() { ResetClaimValuesClosure blk; collection_set_iterate(&blk); } #ifdef ASSERT // This checks whether all regions in the heap have the correct claim // value. I also piggy-backed on this a check to ensure that the // humongous_start_region() information on "continues humongous" // regions is correct. class CheckClaimValuesClosure : public HeapRegionClosure { private: jint _claim_value; uint _failures; HeapRegion* _sh_region; public: CheckClaimValuesClosure(jint claim_value) : _claim_value(claim_value), _failures(0), _sh_region(NULL) { } bool doHeapRegion(HeapRegion* r) { if (r->claim_value() != _claim_value) { gclog_or_tty->print_cr("Region " HR_FORMAT ", " "claim value = %d, should be %d", HR_FORMAT_PARAMS(r), r->claim_value(), _claim_value); ++_failures; } if (!r->isHumongous()) { _sh_region = NULL; } else if (r->startsHumongous()) { _sh_region = r; } else if (r->continuesHumongous()) { if (r->humongous_start_region() != _sh_region) { gclog_or_tty->print_cr("Region " HR_FORMAT ", " "HS = "PTR_FORMAT", should be "PTR_FORMAT, HR_FORMAT_PARAMS(r), r->humongous_start_region(), _sh_region); ++_failures; } } return false; } uint failures() { return _failures; } }; bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { CheckClaimValuesClosure cl(claim_value); heap_region_iterate(&cl); return cl.failures() == 0; } class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { private: jint _claim_value; uint _failures; public: CheckClaimValuesInCSetHRClosure(jint claim_value) : _claim_value(claim_value), _failures(0) { } uint failures() { return _failures; } bool doHeapRegion(HeapRegion* hr) { assert(hr->in_collection_set(), "how?"); assert(!hr->isHumongous(), "H-region in CSet"); if (hr->claim_value() != _claim_value) { gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " "claim value = %d, should be %d", HR_FORMAT_PARAMS(hr), hr->claim_value(), _claim_value); _failures += 1; } return false; } }; bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { CheckClaimValuesInCSetHRClosure cl(claim_value); collection_set_iterate(&cl); return cl.failures() == 0; } #endif // ASSERT // Clear the cached CSet starting regions and (more importantly) // the time stamps. Called when we reset the GC time stamp. void G1CollectedHeap::clear_cset_start_regions() { assert(_worker_cset_start_region != NULL, "sanity"); assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); int n_queues = MAX2((int)ParallelGCThreads, 1); for (int i = 0; i < n_queues; i++) { _worker_cset_start_region[i] = NULL; _worker_cset_start_region_time_stamp[i] = 0; } } // Given the id of a worker, obtain or calculate a suitable // starting region for iterating over the current collection set. HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) { assert(get_gc_time_stamp() > 0, "should have been updated by now"); HeapRegion* result = NULL; unsigned gc_time_stamp = get_gc_time_stamp(); if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { // Cached starting region for current worker was set // during the current pause - so it's valid. // Note: the cached starting heap region may be NULL // (when the collection set is empty). result = _worker_cset_start_region[worker_i]; assert(result == NULL || result->in_collection_set(), "sanity"); return result; } // The cached entry was not valid so let's calculate // a suitable starting heap region for this worker. // We want the parallel threads to start their collection // set iteration at different collection set regions to // avoid contention. // If we have: // n collection set regions // p threads // Then thread t will start at region floor ((t * n) / p) result = g1_policy()->collection_set(); if (G1CollectedHeap::use_parallel_gc_threads()) { uint cs_size = g1_policy()->cset_region_length(); uint active_workers = workers()->active_workers(); assert(UseDynamicNumberOfGCThreads || active_workers == workers()->total_workers(), "Unless dynamic should use total workers"); uint end_ind = (cs_size * worker_i) / active_workers; uint start_ind = 0; if (worker_i > 0 && _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { // Previous workers starting region is valid // so let's iterate from there start_ind = (cs_size * (worker_i - 1)) / active_workers; result = _worker_cset_start_region[worker_i - 1]; } for (uint i = start_ind; i < end_ind; i++) { result = result->next_in_collection_set(); } } // Note: the calculated starting heap region may be NULL // (when the collection set is empty). assert(result == NULL || result->in_collection_set(), "sanity"); assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, "should be updated only once per pause"); _worker_cset_start_region[worker_i] = result; OrderAccess::storestore(); _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; return result; } HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, uint no_of_par_workers) { uint worker_num = G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; assert(UseDynamicNumberOfGCThreads || no_of_par_workers == workers()->total_workers(), "Non dynamic should use fixed number of workers"); const uint start_index = n_regions() * worker_i / worker_num; return region_at(start_index); } void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { HeapRegion* r = g1_policy()->collection_set(); while (r != NULL) { HeapRegion* next = r->next_in_collection_set(); if (cl->doHeapRegion(r)) { cl->incomplete(); return; } r = next; } } void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *cl) { if (r == NULL) { // The CSet is empty so there's nothing to do. return; } assert(r->in_collection_set(), "Start region must be a member of the collection set."); HeapRegion* cur = r; while (cur != NULL) { HeapRegion* next = cur->next_in_collection_set(); if (cl->doHeapRegion(cur) && false) { cl->incomplete(); return; } cur = next; } cur = g1_policy()->collection_set(); while (cur != r) { HeapRegion* next = cur->next_in_collection_set(); if (cl->doHeapRegion(cur) && false) { cl->incomplete(); return; } cur = next; } } CompactibleSpace* G1CollectedHeap::first_compactible_space() { return n_regions() > 0 ? region_at(0) : NULL; } Space* G1CollectedHeap::space_containing(const void* addr) const { Space* res = heap_region_containing(addr); return res; } HeapWord* G1CollectedHeap::block_start(const void* addr) const { Space* sp = space_containing(addr); if (sp != NULL) { return sp->block_start(addr); } return NULL; } size_t G1CollectedHeap::block_size(const HeapWord* addr) const { Space* sp = space_containing(addr); assert(sp != NULL, "block_size of address outside of heap"); return sp->block_size(addr); } bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { Space* sp = space_containing(addr); return sp->block_is_obj(addr); } bool G1CollectedHeap::supports_tlab_allocation() const { return true; } size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { return HeapRegion::GrainBytes; } size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { // Return the remaining space in the cur alloc region, but not less than // the min TLAB size. // Also, this value can be at most the humongous object threshold, // since we can't allow tlabs to grow big enough to accomodate // humongous objects. HeapRegion* hr = _mutator_alloc_region.get(); size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; if (hr == NULL) { return max_tlab_size; } else { return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); } } size_t G1CollectedHeap::max_capacity() const { return _g1_reserved.byte_size(); } jlong G1CollectedHeap::millis_since_last_gc() { // assert(false, "NYI"); return 0; } void G1CollectedHeap::prepare_for_verify() { if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { ensure_parsability(false); } g1_rem_set()->prepare_for_verify(); } bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo) { switch (vo) { case VerifyOption_G1UsePrevMarking: return hr->obj_allocated_since_prev_marking(obj); case VerifyOption_G1UseNextMarking: return hr->obj_allocated_since_next_marking(obj); case VerifyOption_G1UseMarkWord: return false; default: ShouldNotReachHere(); } return false; // keep some compilers happy } HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { switch (vo) { case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); case VerifyOption_G1UseMarkWord: return NULL; default: ShouldNotReachHere(); } return NULL; // keep some compilers happy } bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { switch (vo) { case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); default: ShouldNotReachHere(); } return false; // keep some compilers happy } const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { switch (vo) { case VerifyOption_G1UsePrevMarking: return "PTAMS"; case VerifyOption_G1UseNextMarking: return "NTAMS"; case VerifyOption_G1UseMarkWord: return "NONE"; default: ShouldNotReachHere(); } return NULL; // keep some compilers happy } class VerifyLivenessOopClosure: public OopClosure { G1CollectedHeap* _g1h; VerifyOption _vo; public: VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): _g1h(g1h), _vo(vo) { } void do_oop(narrowOop *p) { do_oop_work(p); } void do_oop( oop *p) { do_oop_work(p); } template void do_oop_work(T *p) { oop obj = oopDesc::load_decode_heap_oop(p); guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), "Dead object referenced by a not dead object"); } }; class VerifyObjsInRegionClosure: public ObjectClosure { private: G1CollectedHeap* _g1h; size_t _live_bytes; HeapRegion *_hr; VerifyOption _vo; public: // _vo == UsePrevMarking -> use "prev" marking information, // _vo == UseNextMarking -> use "next" marking information, // _vo == UseMarkWord -> use mark word from object header. VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) : _live_bytes(0), _hr(hr), _vo(vo) { _g1h = G1CollectedHeap::heap(); } void do_object(oop o) { VerifyLivenessOopClosure isLive(_g1h, _vo); assert(o != NULL, "Huh?"); if (!_g1h->is_obj_dead_cond(o, _vo)) { // If the object is alive according to the mark word, // then verify that the marking information agrees. // Note we can't verify the contra-positive of the // above: if the object is dead (according to the mark // word), it may not be marked, or may have been marked // but has since became dead, or may have been allocated // since the last marking. if (_vo == VerifyOption_G1UseMarkWord) { guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); } o->oop_iterate_no_header(&isLive); if (!_hr->obj_allocated_since_prev_marking(o)) { size_t obj_size = o->size(); // Make sure we don't overflow _live_bytes += (obj_size * HeapWordSize); } } } size_t live_bytes() { return _live_bytes; } }; class PrintObjsInRegionClosure : public ObjectClosure { HeapRegion *_hr; G1CollectedHeap *_g1; public: PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { _g1 = G1CollectedHeap::heap(); }; void do_object(oop o) { if (o != NULL) { HeapWord *start = (HeapWord *) o; size_t word_sz = o->size(); gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", (void*) o, word_sz, _g1->isMarkedPrev(o), _g1->isMarkedNext(o), _hr->obj_allocated_since_prev_marking(o)); HeapWord *end = start + word_sz; HeapWord *cur; int *val; for (cur = start; cur < end; cur++) { val = (int *) cur; gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); } } } }; class VerifyRegionClosure: public HeapRegionClosure { private: bool _par; VerifyOption _vo; bool _failures; public: // _vo == UsePrevMarking -> use "prev" marking information, // _vo == UseNextMarking -> use "next" marking information, // _vo == UseMarkWord -> use mark word from object header. VerifyRegionClosure(bool par, VerifyOption vo) : _par(par), _vo(vo), _failures(false) {} bool failures() { return _failures; } bool doHeapRegion(HeapRegion* r) { if (!r->continuesHumongous()) { bool failures = false; r->verify(_vo, &failures); if (failures) { _failures = true; } else { VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); r->object_iterate(¬_dead_yet_cl); if (_vo != VerifyOption_G1UseNextMarking) { if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " "max_live_bytes "SIZE_FORMAT" " "< calculated "SIZE_FORMAT, r->bottom(), r->end(), r->max_live_bytes(), not_dead_yet_cl.live_bytes()); _failures = true; } } else { // When vo == UseNextMarking we cannot currently do a sanity // check on the live bytes as the calculation has not been // finalized yet. } } } return false; // stop the region iteration if we hit a failure } }; class YoungRefCounterClosure : public OopClosure { G1CollectedHeap* _g1h; int _count; public: YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } void do_oop(narrowOop* p) { ShouldNotReachHere(); } int count() { return _count; } void reset_count() { _count = 0; }; }; class VerifyKlassClosure: public KlassClosure { YoungRefCounterClosure _young_ref_counter_closure; OopClosure *_oop_closure; public: VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} void do_klass(Klass* k) { k->oops_do(_oop_closure); _young_ref_counter_closure.reset_count(); k->oops_do(&_young_ref_counter_closure); if (_young_ref_counter_closure.count() > 0) { guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); } } }; // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can // pass it as the perm_blk to SharedHeap::process_strong_roots. // When process_strong_roots stop calling perm_blk->younger_refs_iterate // we can change this closure to extend the simpler OopClosure. class VerifyRootsClosure: public OopsInGenClosure { private: G1CollectedHeap* _g1h; VerifyOption _vo; bool _failures; public: // _vo == UsePrevMarking -> use "prev" marking information, // _vo == UseNextMarking -> use "next" marking information, // _vo == UseMarkWord -> use mark word from object header. VerifyRootsClosure(VerifyOption vo) : _g1h(G1CollectedHeap::heap()), _vo(vo), _failures(false) { } bool failures() { return _failures; } template void do_oop_nv(T* p) { T heap_oop = oopDesc::load_heap_oop(p); if (!oopDesc::is_null(heap_oop)) { oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); if (_g1h->is_obj_dead_cond(obj, _vo)) { gclog_or_tty->print_cr("Root location "PTR_FORMAT" " "points to dead obj "PTR_FORMAT, p, (void*) obj); if (_vo == VerifyOption_G1UseMarkWord) { gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); } obj->print_on(gclog_or_tty); _failures = true; } } } void do_oop(oop* p) { do_oop_nv(p); } void do_oop(narrowOop* p) { do_oop_nv(p); } }; // This is the task used for parallel heap verification. class G1ParVerifyTask: public AbstractGangTask { private: G1CollectedHeap* _g1h; VerifyOption _vo; bool _failures; public: // _vo == UsePrevMarking -> use "prev" marking information, // _vo == UseNextMarking -> use "next" marking information, // _vo == UseMarkWord -> use mark word from object header. G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : AbstractGangTask("Parallel verify task"), _g1h(g1h), _vo(vo), _failures(false) { } bool failures() { return _failures; } void work(uint worker_id) { HandleMark hm; VerifyRegionClosure blk(true, _vo); _g1h->heap_region_par_iterate_chunked(&blk, worker_id, _g1h->workers()->active_workers(), HeapRegion::ParVerifyClaimValue); if (blk.failures()) { _failures = true; } } }; void G1CollectedHeap::verify(bool silent) { verify(silent, VerifyOption_G1UsePrevMarking); } void G1CollectedHeap::verify(bool silent, VerifyOption vo) { if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { if (!silent) { gclog_or_tty->print("Roots "); } VerifyRootsClosure rootsCl(vo); assert(Thread::current()->is_VM_thread(), "Expected to be executed serially by the VM thread at this point"); CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); VerifyKlassClosure klassCl(this, &rootsCl); // We apply the relevant closures to all the oops in the // system dictionary, the string table and the code cache. const int so = SO_AllClasses | SO_Strings | SO_CodeCache; // Need cleared claim bits for the strong roots processing ClassLoaderDataGraph::clear_claimed_marks(); process_strong_roots(true, // activate StrongRootsScope false, // we set "is scavenging" to false, // so we don't reset the dirty cards. ScanningOption(so), // roots scanning options &rootsCl, &blobsCl, &klassCl ); bool failures = rootsCl.failures(); if (vo != VerifyOption_G1UseMarkWord) { // If we're verifying during a full GC then the region sets // will have been torn down at the start of the GC. Therefore // verifying the region sets will fail. So we only verify // the region sets when not in a full GC. if (!silent) { gclog_or_tty->print("HeapRegionSets "); } verify_region_sets(); } if (!silent) { gclog_or_tty->print("HeapRegions "); } if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity check"); G1ParVerifyTask task(this, vo); assert(UseDynamicNumberOfGCThreads || workers()->active_workers() == workers()->total_workers(), "If not dynamic should be using all the workers"); int n_workers = workers()->active_workers(); set_par_threads(n_workers); workers()->run_task(&task); set_par_threads(0); if (task.failures()) { failures = true; } // Checks that the expected amount of parallel work was done. // The implication is that n_workers is > 0. assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), "sanity check"); reset_heap_region_claim_values(); assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity check"); } else { VerifyRegionClosure blk(false, vo); heap_region_iterate(&blk); if (blk.failures()) { failures = true; } } if (!silent) gclog_or_tty->print("RemSet "); rem_set()->verify(); if (failures) { gclog_or_tty->print_cr("Heap:"); // It helps to have the per-region information in the output to // help us track down what went wrong. This is why we call // print_extended_on() instead of print_on(). print_extended_on(gclog_or_tty); gclog_or_tty->print_cr(""); #ifndef PRODUCT if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { concurrent_mark()->print_reachable("at-verification-failure", vo, false /* all */); } #endif gclog_or_tty->flush(); } guarantee(!failures, "there should not have been any failures"); } else { if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) "); } } class PrintRegionClosure: public HeapRegionClosure { outputStream* _st; public: PrintRegionClosure(outputStream* st) : _st(st) {} bool doHeapRegion(HeapRegion* r) { r->print_on(_st); return false; } }; void G1CollectedHeap::print_on(outputStream* st) const { st->print(" %-20s", "garbage-first heap"); st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", capacity()/K, used_unlocked()/K); st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", _g1_storage.low_boundary(), _g1_storage.high(), _g1_storage.high_boundary()); st->cr(); st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); uint young_regions = _young_list->length(); st->print("%u young (" SIZE_FORMAT "K), ", young_regions, (size_t) young_regions * HeapRegion::GrainBytes / K); uint survivor_regions = g1_policy()->recorded_survivor_regions(); st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, (size_t) survivor_regions * HeapRegion::GrainBytes / K); st->cr(); MetaspaceAux::print_on(st); } void G1CollectedHeap::print_extended_on(outputStream* st) const { print_on(st); // Print the per-region information. st->cr(); st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " "HS=humongous(starts), HC=humongous(continues), " "CS=collection set, F=free, TS=gc time stamp, " "PTAMS=previous top-at-mark-start, " "NTAMS=next top-at-mark-start)"); PrintRegionClosure blk(st); heap_region_iterate(&blk); } void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { if (G1CollectedHeap::use_parallel_gc_threads()) { workers()->print_worker_threads_on(st); } _cmThread->print_on(st); st->cr(); _cm->print_worker_threads_on(st); _cg1r->print_worker_threads_on(st); } void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { if (G1CollectedHeap::use_parallel_gc_threads()) { workers()->threads_do(tc); } tc->do_thread(_cmThread); _cg1r->threads_do(tc); } void G1CollectedHeap::print_tracing_info() const { // We'll overload this to mean "trace GC pause statistics." if (TraceGen0Time || TraceGen1Time) { // The "G1CollectorPolicy" is keeping track of these stats, so delegate // to that. g1_policy()->print_tracing_info(); } if (G1SummarizeRSetStats) { g1_rem_set()->print_summary_info(); } if (G1SummarizeConcMark) { concurrent_mark()->print_summary_info(); } g1_policy()->print_yg_surv_rate_info(); SpecializationStats::print(); } #ifndef PRODUCT // Helpful for debugging RSet issues. class PrintRSetsClosure : public HeapRegionClosure { private: const char* _msg; size_t _occupied_sum; public: bool doHeapRegion(HeapRegion* r) { HeapRegionRemSet* hrrs = r->rem_set(); size_t occupied = hrrs->occupied(); _occupied_sum += occupied; gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, HR_FORMAT_PARAMS(r)); if (occupied == 0) { gclog_or_tty->print_cr(" RSet is empty"); } else { hrrs->print(); } gclog_or_tty->print_cr("----------"); return false; } PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { gclog_or_tty->cr(); gclog_or_tty->print_cr("========================================"); gclog_or_tty->print_cr(msg); gclog_or_tty->cr(); } ~PrintRSetsClosure() { gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); gclog_or_tty->print_cr("========================================"); gclog_or_tty->cr(); } }; void G1CollectedHeap::print_cset_rsets() { PrintRSetsClosure cl("Printing CSet RSets"); collection_set_iterate(&cl); } void G1CollectedHeap::print_all_rsets() { PrintRSetsClosure cl("Printing All RSets");; heap_region_iterate(&cl); } #endif // PRODUCT G1CollectedHeap* G1CollectedHeap::heap() { assert(_sh->kind() == CollectedHeap::G1CollectedHeap, "not a garbage-first heap"); return _g1h; } void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { // always_do_update_barrier = false; assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); // Call allocation profiler AllocationProfiler::iterate_since_last_gc(); // Fill TLAB's and such ensure_parsability(true); } void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { // FIXME: what is this about? // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" // is set. COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), "derived pointer present")); // always_do_update_barrier = true; // We have just completed a GC. Update the soft reference // policy with the new heap occupancy Universe::update_heap_info_at_gc(); } HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, unsigned int gc_count_before, bool* succeeded) { assert_heap_not_locked_and_not_at_safepoint(); g1_policy()->record_stop_world_start(); VM_G1IncCollectionPause op(gc_count_before, word_size, false, /* should_initiate_conc_mark */ g1_policy()->max_pause_time_ms(), GCCause::_g1_inc_collection_pause); VMThread::execute(&op); HeapWord* result = op.result(); bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); assert(result == NULL || ret_succeeded, "the result should be NULL if the VM did not succeed"); *succeeded = ret_succeeded; assert_heap_not_locked(); return result; } void G1CollectedHeap::doConcurrentMark() { MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); if (!_cmThread->in_progress()) { _cmThread->set_started(); CGC_lock->notify(); } } size_t G1CollectedHeap::pending_card_num() { size_t extra_cards = 0; JavaThread *curr = Threads::first(); while (curr != NULL) { DirtyCardQueue& dcq = curr->dirty_card_queue(); extra_cards += dcq.size(); curr = curr->next(); } DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); size_t buffer_size = dcqs.buffer_size(); size_t buffer_num = dcqs.completed_buffers_num(); // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes // in bytes - not the number of 'entries'. We need to convert // into a number of cards. return (buffer_size * buffer_num + extra_cards) / oopSize; } size_t G1CollectedHeap::cards_scanned() { return g1_rem_set()->cardsScanned(); } void G1CollectedHeap::setup_surviving_young_words() { assert(_surviving_young_words == NULL, "pre-condition"); uint array_length = g1_policy()->young_cset_region_length(); _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); if (_surviving_young_words == NULL) { vm_exit_out_of_memory(sizeof(size_t) * array_length, "Not enough space for young surv words summary."); } memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); #ifdef ASSERT for (uint i = 0; i < array_length; ++i) { assert( _surviving_young_words[i] == 0, "memset above" ); } #endif // !ASSERT } void G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); uint array_length = g1_policy()->young_cset_region_length(); for (uint i = 0; i < array_length; ++i) { _surviving_young_words[i] += surv_young_words[i]; } } void G1CollectedHeap::cleanup_surviving_young_words() { guarantee( _surviving_young_words != NULL, "pre-condition" ); FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); _surviving_young_words = NULL; } #ifdef ASSERT class VerifyCSetClosure: public HeapRegionClosure { public: bool doHeapRegion(HeapRegion* hr) { // Here we check that the CSet region's RSet is ready for parallel // iteration. The fields that we'll verify are only manipulated // when the region is part of a CSet and is collected. Afterwards, // we reset these fields when we clear the region's RSet (when the // region is freed) so they are ready when the region is // re-allocated. The only exception to this is if there's an // evacuation failure and instead of freeing the region we leave // it in the heap. In that case, we reset these fields during // evacuation failure handling. guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); // Here's a good place to add any other checks we'd like to // perform on CSet regions. return false; } }; #endif // ASSERT #if TASKQUEUE_STATS void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { st->print_raw_cr("GC Task Stats"); st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); } void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { print_taskqueue_stats_hdr(st); TaskQueueStats totals; const int n = workers() != NULL ? workers()->total_workers() : 1; for (int i = 0; i < n; ++i) { st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); totals += task_queue(i)->stats; } st->print_raw("tot "); totals.print(st); st->cr(); DEBUG_ONLY(totals.verify()); } void G1CollectedHeap::reset_taskqueue_stats() { const int n = workers() != NULL ? workers()->total_workers() : 1; for (int i = 0; i < n; ++i) { task_queue(i)->stats.reset(); } } #endif // TASKQUEUE_STATS void G1CollectedHeap::log_gc_header() { if (!G1Log::fine()) { return; } gclog_or_tty->date_stamp(PrintGCDateStamps); gclog_or_tty->stamp(PrintGCTimeStamps); GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)") .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); gclog_or_tty->print("[%s", (const char*)gc_cause_str); } void G1CollectedHeap::log_gc_footer(double pause_time_sec) { if (!G1Log::fine()) { return; } if (G1Log::finer()) { if (evacuation_failed()) { gclog_or_tty->print(" (to-space exhausted)"); } gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); g1_policy()->phase_times()->note_gc_end(); g1_policy()->phase_times()->print(pause_time_sec); g1_policy()->print_detailed_heap_transition(); } else { if (evacuation_failed()) { gclog_or_tty->print("--"); } g1_policy()->print_heap_transition(); gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); } gclog_or_tty->flush(); } bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { assert_at_safepoint(true /* should_be_vm_thread */); guarantee(!is_gc_active(), "collection is not reentrant"); if (GC_locker::check_active_before_gc()) { return false; } SvcGCMarker sgcm(SvcGCMarker::MINOR); ResourceMark rm; print_heap_before_gc(); HRSPhaseSetter x(HRSPhaseEvacuation); verify_region_sets_optional(); verify_dirty_young_regions(); // This call will decide whether this pause is an initial-mark // pause. If it is, during_initial_mark_pause() will return true // for the duration of this pause. g1_policy()->decide_on_conc_mark_initiation(); // We do not allow initial-mark to be piggy-backed on a mixed GC. assert(!g1_policy()->during_initial_mark_pause() || g1_policy()->gcs_are_young(), "sanity"); // We also do not allow mixed GCs during marking. assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); // Record whether this pause is an initial mark. When the current // thread has completed its logging output and it's safe to signal // the CM thread, the flag's value in the policy has been reset. bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); // Inner scope for scope based logging, timers, and stats collection { if (g1_policy()->during_initial_mark_pause()) { // We are about to start a marking cycle, so we increment the // full collection counter. increment_old_marking_cycles_started(); } TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? workers()->active_workers() : 1); double pause_start_sec = os::elapsedTime(); g1_policy()->phase_times()->note_gc_start(active_workers); log_gc_header(); TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); // If the secondary_free_list is not empty, append it to the // free_list. No need to wait for the cleanup operation to finish; // the region allocation code will check the secondary_free_list // and wait if necessary. If the G1StressConcRegionFreeing flag is // set, skip this step so that the region allocation code has to // get entries from the secondary_free_list. if (!G1StressConcRegionFreeing) { append_secondary_free_list_if_not_empty_with_lock(); } assert(check_young_list_well_formed(), "young list should be well formed"); // Don't dynamically change the number of GC threads this early. A value of // 0 is used to indicate serial work. When parallel work is done, // it will be set. { // Call to jvmpi::post_class_unload_events must occur outside of active GC IsGCActiveMark x; gc_prologue(false); increment_total_collections(false /* full gc */); increment_gc_time_stamp(); verify_before_gc(); COMPILER2_PRESENT(DerivedPointerTable::clear()); // Please see comment in g1CollectedHeap.hpp and // G1CollectedHeap::ref_processing_init() to see how // reference processing currently works in G1. // Enable discovery in the STW reference processor ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); { // We want to temporarily turn off discovery by the // CM ref processor, if necessary, and turn it back on // on again later if we do. Using a scoped // NoRefDiscovery object will do this. NoRefDiscovery no_cm_discovery(ref_processor_cm()); // Forget the current alloc region (we might even choose it to be part // of the collection set!). release_mutator_alloc_region(); // We should call this after we retire the mutator alloc // region(s) so that all the ALLOC / RETIRE events are generated // before the start GC event. _hr_printer.start_gc(false /* full */, (size_t) total_collections()); // This timing is only used by the ergonomics to handle our pause target. // It is unclear why this should not include the full pause. We will // investigate this in CR 7178365. // // Preserving the old comment here if that helps the investigation: // // The elapsed time induced by the start time below deliberately elides // the possible verification above. double sample_start_time_sec = os::elapsedTime(); size_t start_used_bytes = used(); #if YOUNG_LIST_VERBOSE gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); _young_list->print(); g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); #endif // YOUNG_LIST_VERBOSE g1_policy()->record_collection_pause_start(sample_start_time_sec, start_used_bytes); double scan_wait_start = os::elapsedTime(); // We have to wait until the CM threads finish scanning the // root regions as it's the only way to ensure that all the // objects on them have been correctly scanned before we start // moving them during the GC. bool waited = _cm->root_regions()->wait_until_scan_finished(); double wait_time_ms = 0.0; if (waited) { double scan_wait_end = os::elapsedTime(); wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; } g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); #if YOUNG_LIST_VERBOSE gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); _young_list->print(); #endif // YOUNG_LIST_VERBOSE if (g1_policy()->during_initial_mark_pause()) { concurrent_mark()->checkpointRootsInitialPre(); } #if YOUNG_LIST_VERBOSE gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); _young_list->print(); g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); #endif // YOUNG_LIST_VERBOSE g1_policy()->finalize_cset(target_pause_time_ms); _cm->note_start_of_gc(); // We should not verify the per-thread SATB buffers given that // we have not filtered them yet (we'll do so during the // GC). We also call this after finalize_cset() to // ensure that the CSet has been finalized. _cm->verify_no_cset_oops(true /* verify_stacks */, true /* verify_enqueued_buffers */, false /* verify_thread_buffers */, true /* verify_fingers */); if (_hr_printer.is_active()) { HeapRegion* hr = g1_policy()->collection_set(); while (hr != NULL) { G1HRPrinter::RegionType type; if (!hr->is_young()) { type = G1HRPrinter::Old; } else if (hr->is_survivor()) { type = G1HRPrinter::Survivor; } else { type = G1HRPrinter::Eden; } _hr_printer.cset(hr); hr = hr->next_in_collection_set(); } } #ifdef ASSERT VerifyCSetClosure cl; collection_set_iterate(&cl); #endif // ASSERT setup_surviving_young_words(); // Initialize the GC alloc regions. init_gc_alloc_regions(); // Actually do the work... evacuate_collection_set(); // We do this to mainly verify the per-thread SATB buffers // (which have been filtered by now) since we didn't verify // them earlier. No point in re-checking the stacks / enqueued // buffers given that the CSet has not changed since last time // we checked. _cm->verify_no_cset_oops(false /* verify_stacks */, false /* verify_enqueued_buffers */, true /* verify_thread_buffers */, true /* verify_fingers */); free_collection_set(g1_policy()->collection_set()); g1_policy()->clear_collection_set(); cleanup_surviving_young_words(); // Start a new incremental collection set for the next pause. g1_policy()->start_incremental_cset_building(); // Clear the _cset_fast_test bitmap in anticipation of adding // regions to the incremental collection set for the next // evacuation pause. clear_cset_fast_test(); _young_list->reset_sampled_info(); // Don't check the whole heap at this point as the // GC alloc regions from this pause have been tagged // as survivors and moved on to the survivor list. // Survivor regions will fail the !is_young() check. assert(check_young_list_empty(false /* check_heap */), "young list should be empty"); #if YOUNG_LIST_VERBOSE gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); _young_list->print(); #endif // YOUNG_LIST_VERBOSE g1_policy()->record_survivor_regions(_young_list->survivor_length(), _young_list->first_survivor_region(), _young_list->last_survivor_region()); _young_list->reset_auxilary_lists(); if (evacuation_failed()) { _summary_bytes_used = recalculate_used(); } else { // The "used" of the the collection set have already been subtracted // when they were freed. Add in the bytes evacuated. _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); } if (g1_policy()->during_initial_mark_pause()) { // We have to do this before we notify the CM threads that // they can start working to make sure that all the // appropriate initialization is done on the CM object. concurrent_mark()->checkpointRootsInitialPost(); set_marking_started(); // Note that we don't actually trigger the CM thread at // this point. We do that later when we're sure that // the current thread has completed its logging output. } allocate_dummy_regions(); #if YOUNG_LIST_VERBOSE gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); _young_list->print(); g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); #endif // YOUNG_LIST_VERBOSE init_mutator_alloc_region(); { size_t expand_bytes = g1_policy()->expansion_amount(); if (expand_bytes > 0) { size_t bytes_before = capacity(); // No need for an ergo verbose message here, // expansion_amount() does this when it returns a value > 0. if (!expand(expand_bytes)) { // We failed to expand the heap so let's verify that // committed/uncommitted amount match the backing store assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); } } } // We redo the verificaiton but now wrt to the new CSet which // has just got initialized after the previous CSet was freed. _cm->verify_no_cset_oops(true /* verify_stacks */, true /* verify_enqueued_buffers */, true /* verify_thread_buffers */, true /* verify_fingers */); _cm->note_end_of_gc(); // This timing is only used by the ergonomics to handle our pause target. // It is unclear why this should not include the full pause. We will // investigate this in CR 7178365. double sample_end_time_sec = os::elapsedTime(); double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; g1_policy()->record_collection_pause_end(pause_time_ms); MemoryService::track_memory_usage(); // In prepare_for_verify() below we'll need to scan the deferred // update buffers to bring the RSets up-to-date if // G1HRRSFlushLogBuffersOnVerify has been set. While scanning // the update buffers we'll probably need to scan cards on the // regions we just allocated to (i.e., the GC alloc // regions). However, during the last GC we called // set_saved_mark() on all the GC alloc regions, so card // scanning might skip the [saved_mark_word()...top()] area of // those regions (i.e., the area we allocated objects into // during the last GC). But it shouldn't. Given that // saved_mark_word() is conditional on whether the GC time stamp // on the region is current or not, by incrementing the GC time // stamp here we invalidate all the GC time stamps on all the // regions and saved_mark_word() will simply return top() for // all the regions. This is a nicer way of ensuring this rather // than iterating over the regions and fixing them. In fact, the // GC time stamp increment here also ensures that // saved_mark_word() will return top() between pauses, i.e., // during concurrent refinement. So we don't need the // is_gc_active() check to decided which top to use when // scanning cards (see CR 7039627). increment_gc_time_stamp(); verify_after_gc(); assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); ref_processor_stw()->verify_no_references_recorded(); // CM reference discovery will be re-enabled if necessary. } // We should do this after we potentially expand the heap so // that all the COMMIT events are generated before the end GC // event, and after we retire the GC alloc regions so that all // RETIRE events are generated before the end GC event. _hr_printer.end_gc(false /* full */, (size_t) total_collections()); if (mark_in_progress()) { concurrent_mark()->update_g1_committed(); } #ifdef TRACESPINNING ParallelTaskTerminator::print_termination_counts(); #endif gc_epilogue(false); } // Print the remainder of the GC log output. log_gc_footer(os::elapsedTime() - pause_start_sec); // It is not yet to safe to tell the concurrent mark to // start as we have some optional output below. We don't want the // output from the concurrent mark thread interfering with this // logging output either. _hrs.verify_optional(); verify_region_sets_optional(); TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); print_heap_after_gc(); // We must call G1MonitoringSupport::update_sizes() in the same scoping level // as an active TraceMemoryManagerStats object (i.e. before the destructor for the // TraceMemoryManagerStats is called) so that the G1 memory pools are updated // before any GC notifications are raised. g1mm()->update_sizes(); } if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { g1_rem_set()->print_summary_info(); } // It should now be safe to tell the concurrent mark thread to start // without its logging output interfering with the logging output // that came from the pause. if (should_start_conc_mark) { // CAUTION: after the doConcurrentMark() call below, // the concurrent marking thread(s) could be running // concurrently with us. Make sure that anything after // this point does not assume that we are the only GC thread // running. Note: of course, the actual marking work will // not start until the safepoint itself is released in // ConcurrentGCThread::safepoint_desynchronize(). doConcurrentMark(); } return true; } size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) { size_t gclab_word_size; switch (purpose) { case GCAllocForSurvived: gclab_word_size = _survivor_plab_stats.desired_plab_sz(); break; case GCAllocForTenured: gclab_word_size = _old_plab_stats.desired_plab_sz(); break; default: assert(false, "unknown GCAllocPurpose"); gclab_word_size = _old_plab_stats.desired_plab_sz(); break; } // Prevent humongous PLAB sizes for two reasons: // * PLABs are allocated using a similar paths as oops, but should // never be in a humongous region // * Allowing humongous PLABs needlessly churns the region free lists return MIN2(_humongous_object_threshold_in_words, gclab_word_size); } void G1CollectedHeap::init_mutator_alloc_region() { assert(_mutator_alloc_region.get() == NULL, "pre-condition"); _mutator_alloc_region.init(); } void G1CollectedHeap::release_mutator_alloc_region() { _mutator_alloc_region.release(); assert(_mutator_alloc_region.get() == NULL, "post-condition"); } void G1CollectedHeap::init_gc_alloc_regions() { assert_at_safepoint(true /* should_be_vm_thread */); _survivor_gc_alloc_region.init(); _old_gc_alloc_region.init(); HeapRegion* retained_region = _retained_old_gc_alloc_region; _retained_old_gc_alloc_region = NULL; // We will discard the current GC alloc region if: // a) it's in the collection set (it can happen!), // b) it's already full (no point in using it), // c) it's empty (this means that it was emptied during // a cleanup and it should be on the free list now), or // d) it's humongous (this means that it was emptied // during a cleanup and was added to the free list, but // has been subseqently used to allocate a humongous // object that may be less than the region size). if (retained_region != NULL && !retained_region->in_collection_set() && !(retained_region->top() == retained_region->end()) && !retained_region->is_empty() && !retained_region->isHumongous()) { retained_region->set_saved_mark(); // The retained region was added to the old region set when it was // retired. We have to remove it now, since we don't allow regions // we allocate to in the region sets. We'll re-add it later, when // it's retired again. _old_set.remove(retained_region); bool during_im = g1_policy()->during_initial_mark_pause(); retained_region->note_start_of_copying(during_im); _old_gc_alloc_region.set(retained_region); _hr_printer.reuse(retained_region); } } void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers) { _survivor_gc_alloc_region.release(); // If we have an old GC alloc region to release, we'll save it in // _retained_old_gc_alloc_region. If we don't // _retained_old_gc_alloc_region will become NULL. This is what we // want either way so no reason to check explicitly for either // condition. _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); if (ResizePLAB) { _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); } } void G1CollectedHeap::abandon_gc_alloc_regions() { assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); _retained_old_gc_alloc_region = NULL; } void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { _drain_in_progress = false; set_evac_failure_closure(cl); _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray(40, true); } void G1CollectedHeap::finalize_for_evac_failure() { assert(_evac_failure_scan_stack != NULL && _evac_failure_scan_stack->length() == 0, "Postcondition"); assert(!_drain_in_progress, "Postcondition"); delete _evac_failure_scan_stack; _evac_failure_scan_stack = NULL; } void G1CollectedHeap::remove_self_forwarding_pointers() { assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); G1ParRemoveSelfForwardPtrsTask rsfp_task(this); if (G1CollectedHeap::use_parallel_gc_threads()) { set_par_threads(); workers()->run_task(&rsfp_task); set_par_threads(0); } else { rsfp_task.work(0); } assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); // Reset the claim values in the regions in the collection set. reset_cset_heap_region_claim_values(); assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); // Now restore saved marks, if any. if (_objs_with_preserved_marks != NULL) { assert(_preserved_marks_of_objs != NULL, "Both or none."); guarantee(_objs_with_preserved_marks->length() == _preserved_marks_of_objs->length(), "Both or none."); for (int i = 0; i < _objs_with_preserved_marks->length(); i++) { oop obj = _objs_with_preserved_marks->at(i); markOop m = _preserved_marks_of_objs->at(i); obj->set_mark(m); } // Delete the preserved marks growable arrays (allocated on the C heap). delete _objs_with_preserved_marks; delete _preserved_marks_of_objs; _objs_with_preserved_marks = NULL; _preserved_marks_of_objs = NULL; } } void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { _evac_failure_scan_stack->push(obj); } void G1CollectedHeap::drain_evac_failure_scan_stack() { assert(_evac_failure_scan_stack != NULL, "precondition"); while (_evac_failure_scan_stack->length() > 0) { oop obj = _evac_failure_scan_stack->pop(); _evac_failure_closure->set_region(heap_region_containing(obj)); obj->oop_iterate_backwards(_evac_failure_closure); } } oop G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop old) { assert(obj_in_cs(old), err_msg("obj: "PTR_FORMAT" should still be in the CSet", (HeapWord*) old)); markOop m = old->mark(); oop forward_ptr = old->forward_to_atomic(old); if (forward_ptr == NULL) { // Forward-to-self succeeded. if (_evac_failure_closure != cl) { MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); assert(!_drain_in_progress, "Should only be true while someone holds the lock."); // Set the global evac-failure closure to the current thread's. assert(_evac_failure_closure == NULL, "Or locking has failed."); set_evac_failure_closure(cl); // Now do the common part. handle_evacuation_failure_common(old, m); // Reset to NULL. set_evac_failure_closure(NULL); } else { // The lock is already held, and this is recursive. assert(_drain_in_progress, "This should only be the recursive case."); handle_evacuation_failure_common(old, m); } return old; } else { // Forward-to-self failed. Either someone else managed to allocate // space for this object (old != forward_ptr) or they beat us in // self-forwarding it (old == forward_ptr). assert(old == forward_ptr || !obj_in_cs(forward_ptr), err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " "should not be in the CSet", (HeapWord*) old, (HeapWord*) forward_ptr)); return forward_ptr; } } void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { set_evacuation_failed(true); preserve_mark_if_necessary(old, m); HeapRegion* r = heap_region_containing(old); if (!r->evacuation_failed()) { r->set_evacuation_failed(true); _hr_printer.evac_failure(r); } push_on_evac_failure_scan_stack(old); if (!_drain_in_progress) { // prevent recursion in copy_to_survivor_space() _drain_in_progress = true; drain_evac_failure_scan_stack(); _drain_in_progress = false; } } void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { assert(evacuation_failed(), "Oversaving!"); // We want to call the "for_promotion_failure" version only in the // case of a promotion failure. if (m->must_be_preserved_for_promotion_failure(obj)) { if (_objs_with_preserved_marks == NULL) { assert(_preserved_marks_of_objs == NULL, "Both or none."); _objs_with_preserved_marks = new (ResourceObj::C_HEAP, mtGC) GrowableArray(40, true); _preserved_marks_of_objs = new (ResourceObj::C_HEAP, mtGC) GrowableArray(40, true); } _objs_with_preserved_marks->push(obj); _preserved_marks_of_objs->push(m); } } HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size) { if (purpose == GCAllocForSurvived) { HeapWord* result = survivor_attempt_allocation(word_size); if (result != NULL) { return result; } else { // Let's try to allocate in the old gen in case we can fit the // object there. return old_attempt_allocation(word_size); } } else { assert(purpose == GCAllocForTenured, "sanity"); HeapWord* result = old_attempt_allocation(word_size); if (result != NULL) { return result; } else { // Let's try to allocate in the survivors in case we can fit the // object there. return survivor_attempt_allocation(word_size); } } ShouldNotReachHere(); // Trying to keep some compilers happy. return NULL; } G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : ParGCAllocBuffer(gclab_word_size), _retired(false) { } G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num) : _g1h(g1h), _refs(g1h->task_queue(queue_num)), _dcq(&g1h->dirty_card_queue_set()), _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), _g1_rem(g1h->g1_rem_set()), _hash_seed(17), _queue_num(queue_num), _term_attempts(0), _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), _age_table(false), _strong_roots_time(0), _term_time(0), _alloc_buffer_waste(0), _undo_waste(0) { // we allocate G1YoungSurvRateNumRegions plus one entries, since // we "sacrifice" entry 0 to keep track of surviving bytes for // non-young regions (where the age is -1) // We also add a few elements at the beginning and at the end in // an attempt to eliminate cache contention uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); uint array_length = PADDING_ELEM_NUM + real_length + PADDING_ELEM_NUM; _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); if (_surviving_young_words_base == NULL) vm_exit_out_of_memory(array_length * sizeof(size_t), "Not enough space for young surv histo."); _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; _start = os::elapsedTime(); } void G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) { st->print_raw_cr("GC Termination Stats"); st->print_raw_cr(" elapsed --strong roots-- -------termination-------" " ------waste (KiB)------"); st->print_raw_cr("thr ms ms % ms % attempts" " total alloc undo"); st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" " ------- ------- -------"); } void G1ParScanThreadState::print_termination_stats(int i, outputStream* const st) const { const double elapsed_ms = elapsed_time() * 1000.0; const double s_roots_ms = strong_roots_time() * 1000.0; const double term_ms = term_time() * 1000.0; st->print_cr("%3d %9.2f %9.2f %6.2f " "%9.2f %6.2f " SIZE_FORMAT_W(8) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, term_ms, term_ms * 100 / elapsed_ms, term_attempts(), (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, alloc_buffer_waste() * HeapWordSize / K, undo_waste() * HeapWordSize / K); } #ifdef ASSERT bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { assert(ref != NULL, "invariant"); assert(UseCompressedOops, "sanity"); assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); oop p = oopDesc::load_decode_heap_oop(ref); assert(_g1h->is_in_g1_reserved(p), err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); return true; } bool G1ParScanThreadState::verify_ref(oop* ref) const { assert(ref != NULL, "invariant"); if (has_partial_array_mask(ref)) { // Must be in the collection set--it's already been copied. oop p = clear_partial_array_mask(ref); assert(_g1h->obj_in_cs(p), err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); } else { oop p = oopDesc::load_decode_heap_oop(ref); assert(_g1h->is_in_g1_reserved(p), err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); } return true; } bool G1ParScanThreadState::verify_task(StarTask ref) const { if (ref.is_narrow()) { return verify_ref((narrowOop*) ref); } else { return verify_ref((oop*) ref); } } #endif // ASSERT void G1ParScanThreadState::trim_queue() { assert(_evac_cl != NULL, "not set"); assert(_evac_failure_cl != NULL, "not set"); assert(_partial_scan_cl != NULL, "not set"); StarTask ref; do { // Drain the overflow stack first, so other threads can steal. while (refs()->pop_overflow(ref)) { deal_with_reference(ref); } while (refs()->pop_local(ref)) { deal_with_reference(ref); } } while (!refs()->is_empty()); } G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) : _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), _par_scan_state(par_scan_state), _worker_id(par_scan_state->queue_num()), _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()), _mark_in_progress(_g1->mark_in_progress()) { } template void G1ParCopyClosure::mark_object(oop obj) { #ifdef ASSERT HeapRegion* hr = _g1->heap_region_containing(obj); assert(hr != NULL, "sanity"); assert(!hr->in_collection_set(), "should not mark objects in the CSet"); #endif // ASSERT // We know that the object is not moving so it's safe to read its size. _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); } template void G1ParCopyClosure ::mark_forwarded_object(oop from_obj, oop to_obj) { #ifdef ASSERT assert(from_obj->is_forwarded(), "from obj should be forwarded"); assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); assert(from_obj != to_obj, "should not be self-forwarded"); HeapRegion* from_hr = _g1->heap_region_containing(from_obj); assert(from_hr != NULL, "sanity"); assert(from_hr->in_collection_set(), "from obj should be in the CSet"); HeapRegion* to_hr = _g1->heap_region_containing(to_obj); assert(to_hr != NULL, "sanity"); assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); #endif // ASSERT // The object might be in the process of being copied by another // worker so we cannot trust that its to-space image is // well-formed. So we have to read its size from its from-space // image which we know should not be changing. _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); } template oop G1ParCopyClosure ::copy_to_survivor_space(oop old) { size_t word_sz = old->size(); HeapRegion* from_region = _g1->heap_region_containing_raw(old); // +1 to make the -1 indexes valid... int young_index = from_region->young_index_in_cset()+1; assert( (from_region->is_young() && young_index > 0) || (!from_region->is_young() && young_index == 0), "invariant" ); G1CollectorPolicy* g1p = _g1->g1_policy(); markOop m = old->mark(); int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() : m->age(); GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, word_sz); HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); #ifndef PRODUCT // Should this evacuation fail? if (_g1->evacuation_should_fail()) { if (obj_ptr != NULL) { _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); obj_ptr = NULL; } } #endif // !PRODUCT if (obj_ptr == NULL) { // This will either forward-to-self, or detect that someone else has // installed a forwarding pointer. OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); return _g1->handle_evacuation_failure_par(cl, old); } oop obj = oop(obj_ptr); // We're going to allocate linearly, so might as well prefetch ahead. Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); oop forward_ptr = old->forward_to_atomic(obj); if (forward_ptr == NULL) { Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); if (g1p->track_object_age(alloc_purpose)) { // We could simply do obj->incr_age(). However, this causes a // performance issue. obj->incr_age() will first check whether // the object has a displaced mark by checking its mark word; // getting the mark word from the new location of the object // stalls. So, given that we already have the mark word and we // are about to install it anyway, it's better to increase the // age on the mark word, when the object does not have a // displaced mark word. We're not expecting many objects to have // a displaced marked word, so that case is not optimized // further (it could be...) and we simply call obj->incr_age(). if (m->has_displaced_mark_helper()) { // in this case, we have to install the mark word first, // otherwise obj looks to be forwarded (the old mark word, // which contains the forward pointer, was copied) obj->set_mark(m); obj->incr_age(); } else { m = m->incr_age(); obj->set_mark(m); } _par_scan_state->age_table()->add(obj, word_sz); } else { obj->set_mark(m); } size_t* surv_young_words = _par_scan_state->surviving_young_words(); surv_young_words[young_index] += word_sz; if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { // We keep track of the next start index in the length field of // the to-space object. The actual length can be found in the // length field of the from-space object. arrayOop(obj)->set_length(0); oop* old_p = set_partial_array_mask(old); _par_scan_state->push_on_queue(old_p); } else { // No point in using the slower heap_region_containing() method, // given that we know obj is in the heap. _scanner.set_region(_g1->heap_region_containing_raw(obj)); obj->oop_iterate_backwards(&_scanner); } } else { _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); obj = forward_ptr; } return obj; } template void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { if (_g1->heap_region_containing_raw(new_obj)->is_young()) { _scanned_klass->record_modified_oops(); } } template template void G1ParCopyClosure ::do_oop_work(T* p) { oop obj = oopDesc::load_decode_heap_oop(p); assert(barrier != G1BarrierRS || obj != NULL, "Precondition: G1BarrierRS implies obj is non-NULL"); assert(_worker_id == _par_scan_state->queue_num(), "sanity"); // here the null check is implicit in the cset_fast_test() test if (_g1->in_cset_fast_test(obj)) { oop forwardee; if (obj->is_forwarded()) { forwardee = obj->forwardee(); } else { forwardee = copy_to_survivor_space(obj); } assert(forwardee != NULL, "forwardee should not be NULL"); oopDesc::encode_store_heap_oop(p, forwardee); if (do_mark_object && forwardee != obj) { // If the object is self-forwarded we don't need to explicitly // mark it, the evacuation failure protocol will do so. mark_forwarded_object(obj, forwardee); } // When scanning the RS, we only care about objs in CS. if (barrier == G1BarrierRS) { _par_scan_state->update_rs(_from, p, _worker_id); } else if (barrier == G1BarrierKlass) { do_klass_barrier(p, forwardee); } } else { // The object is not in collection set. If we're a root scanning // closure during an initial mark pause (i.e. do_mark_object will // be true) then attempt to mark the object. if (do_mark_object && _g1->is_in_g1_reserved(obj)) { mark_object(obj); } } if (barrier == G1BarrierEvac && obj != NULL) { _par_scan_state->update_rs(_from, p, _worker_id); } if (do_gen_barrier && obj != NULL) { par_do_barrier(p); } } template void G1ParCopyClosure::do_oop_work(oop* p); template void G1ParCopyClosure::do_oop_work(narrowOop* p); template void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { assert(has_partial_array_mask(p), "invariant"); oop from_obj = clear_partial_array_mask(p); assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap."); assert(from_obj->is_objArray(), "must be obj array"); objArrayOop from_obj_array = objArrayOop(from_obj); // The from-space object contains the real length. int length = from_obj_array->length(); assert(from_obj->is_forwarded(), "must be forwarded"); oop to_obj = from_obj->forwardee(); assert(from_obj != to_obj, "should not be chunking self-forwarded objects"); objArrayOop to_obj_array = objArrayOop(to_obj); // We keep track of the next start index in the length field of the // to-space object. int next_index = to_obj_array->length(); assert(0 <= next_index && next_index < length, err_msg("invariant, next index: %d, length: %d", next_index, length)); int start = next_index; int end = length; int remainder = end - start; // We'll try not to push a range that's smaller than ParGCArrayScanChunk. if (remainder > 2 * ParGCArrayScanChunk) { end = start + ParGCArrayScanChunk; to_obj_array->set_length(end); // Push the remainder before we process the range in case another // worker has run out of things to do and can steal it. oop* from_obj_p = set_partial_array_mask(from_obj); _par_scan_state->push_on_queue(from_obj_p); } else { assert(length == end, "sanity"); // We'll process the final range for this object. Restore the length // so that the heap remains parsable in case of evacuation failure. to_obj_array->set_length(end); } _scanner.set_region(_g1->heap_region_containing_raw(to_obj)); // Process indexes [start,end). It will also process the header // along with the first chunk (i.e., the chunk with start == 0). // Note that at this point the length field of to_obj_array is not // correct given that we are using it to keep track of the next // start index. oop_iterate_range() (thankfully!) ignores the length // field and only relies on the start / end parameters. It does // however return the size of the object which will be incorrect. So // we have to ignore it even if we wanted to use it. to_obj_array->oop_iterate_range(&_scanner, start, end); } class G1ParEvacuateFollowersClosure : public VoidClosure { protected: G1CollectedHeap* _g1h; G1ParScanThreadState* _par_scan_state; RefToScanQueueSet* _queues; ParallelTaskTerminator* _terminator; G1ParScanThreadState* par_scan_state() { return _par_scan_state; } RefToScanQueueSet* queues() { return _queues; } ParallelTaskTerminator* terminator() { return _terminator; } public: G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, G1ParScanThreadState* par_scan_state, RefToScanQueueSet* queues, ParallelTaskTerminator* terminator) : _g1h(g1h), _par_scan_state(par_scan_state), _queues(queues), _terminator(terminator) {} void do_void(); private: inline bool offer_termination(); }; bool G1ParEvacuateFollowersClosure::offer_termination() { G1ParScanThreadState* const pss = par_scan_state(); pss->start_term_time(); const bool res = terminator()->offer_termination(); pss->end_term_time(); return res; } void G1ParEvacuateFollowersClosure::do_void() { StarTask stolen_task; G1ParScanThreadState* const pss = par_scan_state(); pss->trim_queue(); do { while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { assert(pss->verify_task(stolen_task), "sanity"); if (stolen_task.is_narrow()) { pss->deal_with_reference((narrowOop*) stolen_task); } else { pss->deal_with_reference((oop*) stolen_task); } // We've just processed a reference and we might have made // available new entries on the queues. So we have to make sure // we drain the queues as necessary. pss->trim_queue(); } } while (!offer_termination()); pss->retire_alloc_buffers(); } class G1KlassScanClosure : public KlassClosure { G1ParCopyHelper* _closure; bool _process_only_dirty; int _count; public: G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} void do_klass(Klass* klass) { // If the klass has not been dirtied we know that there's // no references into the young gen and we can skip it. if (!_process_only_dirty || klass->has_modified_oops()) { // Clean the klass since we're going to scavenge all the metadata. klass->clear_modified_oops(); // Tell the closure that this klass is the Klass to scavenge // and is the one to dirty if oops are left pointing into the young gen. _closure->set_scanned_klass(klass); klass->oops_do(_closure); _closure->set_scanned_klass(NULL); } _count++; } }; class G1ParTask : public AbstractGangTask { protected: G1CollectedHeap* _g1h; RefToScanQueueSet *_queues; ParallelTaskTerminator _terminator; uint _n_workers; Mutex _stats_lock; Mutex* stats_lock() { return &_stats_lock; } size_t getNCards() { return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) / G1BlockOffsetSharedArray::N_bytes; } public: G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues) : AbstractGangTask("G1 collection"), _g1h(g1h), _queues(task_queues), _terminator(0, _queues), _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) {} RefToScanQueueSet* queues() { return _queues; } RefToScanQueue *work_queue(int i) { return queues()->queue(i); } ParallelTaskTerminator* terminator() { return &_terminator; } virtual void set_for_termination(int active_workers) { // This task calls set_n_termination() in par_non_clean_card_iterate_work() // in the young space (_par_seq_tasks) in the G1 heap // for SequentialSubTasksDone. // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap // both of which need setting by set_n_termination(). _g1h->SharedHeap::set_n_termination(active_workers); _g1h->set_n_termination(active_workers); terminator()->reset_for_reuse(active_workers); _n_workers = active_workers; } void work(uint worker_id) { if (worker_id >= _n_workers) return; // no work needed this round double start_time_ms = os::elapsedTime() * 1000.0; _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); { ResourceMark rm; HandleMark hm; ReferenceProcessor* rp = _g1h->ref_processor_stw(); G1ParScanThreadState pss(_g1h, worker_id); G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp); G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp); pss.set_evac_closure(&scan_evac_cl); pss.set_evac_failure_closure(&evac_failure_cl); pss.set_partial_scan_closure(&partial_scan_cl); G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); bool only_young = _g1h->g1_policy()->gcs_are_young(); G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); OopClosure* scan_root_cl = &only_scan_root_cl; G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; if (_g1h->g1_policy()->during_initial_mark_pause()) { // We also need to mark copied objects. scan_root_cl = &scan_mark_root_cl; scan_klasses_cl = &scan_mark_klasses_cl_s; } G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; pss.start_strong_roots(); _g1h->g1_process_strong_roots(/* is scavenging */ true, SharedHeap::ScanningOption(so), scan_root_cl, &push_heap_rs_cl, scan_klasses_cl, worker_id); pss.end_strong_roots(); { double start = os::elapsedTime(); G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); evac.do_void(); double elapsed_ms = (os::elapsedTime()-start)*1000.0; double term_ms = pss.term_time()*1000.0; _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); } _g1h->g1_policy()->record_thread_age_table(pss.age_table()); _g1h->update_surviving_young_words(pss.surviving_young_words()+1); if (ParallelGCVerbose) { MutexLocker x(stats_lock()); pss.print_termination_stats(worker_id); } assert(pss.refs()->is_empty(), "should be empty"); // Close the inner scope so that the ResourceMark and HandleMark // destructors are executed here and are included as part of the // "GC Worker Time". } double end_time_ms = os::elapsedTime() * 1000.0; _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); } }; // *** Common G1 Evacuation Stuff // Closures that support the filtering of CodeBlobs scanned during // external root scanning. // Closure applied to reference fields in code blobs (specifically nmethods) // to determine whether an nmethod contains references that point into // the collection set. Used as a predicate when walking code roots so // that only nmethods that point into the collection set are added to the // 'marked' list. class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure { class G1PointsIntoCSOopClosure : public OopClosure { G1CollectedHeap* _g1; bool _points_into_cs; public: G1PointsIntoCSOopClosure(G1CollectedHeap* g1) : _g1(g1), _points_into_cs(false) { } bool points_into_cs() const { return _points_into_cs; } template void do_oop_nv(T* p) { if (!_points_into_cs) { T heap_oop = oopDesc::load_heap_oop(p); if (!oopDesc::is_null(heap_oop) && _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) { _points_into_cs = true; } } } virtual void do_oop(oop* p) { do_oop_nv(p); } virtual void do_oop(narrowOop* p) { do_oop_nv(p); } }; G1CollectedHeap* _g1; public: G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) : CodeBlobToOopClosure(cl, true), _g1(g1) { } virtual void do_code_blob(CodeBlob* cb) { nmethod* nm = cb->as_nmethod_or_null(); if (nm != NULL && !(nm->test_oops_do_mark())) { G1PointsIntoCSOopClosure predicate_cl(_g1); nm->oops_do(&predicate_cl); if (predicate_cl.points_into_cs()) { // At least one of the reference fields or the oop relocations // in the nmethod points into the collection set. We have to // 'mark' this nmethod. // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob() // or MarkingCodeBlobClosure::do_code_blob() change. if (!nm->test_set_oops_do_mark()) { do_newly_marked_nmethod(nm); } } } } }; // This method is run in a GC worker. void G1CollectedHeap:: g1_process_strong_roots(bool is_scavenging, ScanningOption so, OopClosure* scan_non_heap_roots, OopsInHeapRegionClosure* scan_rs, G1KlassScanClosure* scan_klasses, int worker_i) { // First scan the strong roots double ext_roots_start = os::elapsedTime(); double closure_app_time_sec = 0.0; BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); // Walk the code cache w/o buffering, because StarTask cannot handle // unaligned oop locations. G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots); process_strong_roots(false, // no scoping; this is parallel code is_scavenging, so, &buf_scan_non_heap_roots, &eager_scan_code_roots, scan_klasses ); // Now the CM ref_processor roots. if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { // We need to treat the discovered reference lists of the // concurrent mark ref processor as roots and keep entries // (which are added by the marking threads) on them live // until they can be processed at the end of marking. ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); } // Finish up any enqueued closure apps (attributed as object copy time). buf_scan_non_heap_roots.done(); double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); double ext_root_time_ms = ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); // During conc marking we have to filter the per-thread SATB buffers // to make sure we remove any oops into the CSet (which will show up // as implicitly live). double satb_filtering_ms = 0.0; if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { if (mark_in_progress()) { double satb_filter_start = os::elapsedTime(); JavaThread::satb_mark_queue_set().filter_thread_buffers(); satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; } } g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); // Now scan the complement of the collection set. if (scan_rs != NULL) { g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); } _process_strong_tasks->all_tasks_completed(); } void G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure, OopClosure* non_root_closure) { CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure); } // Weak Reference Processing support // An always "is_alive" closure that is used to preserve referents. // If the object is non-null then it's alive. Used in the preservation // of referent objects that are pointed to by reference objects // discovered by the CM ref processor. class G1AlwaysAliveClosure: public BoolObjectClosure { G1CollectedHeap* _g1; public: G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} void do_object(oop p) { assert(false, "Do not call."); } bool do_object_b(oop p) { if (p != NULL) { return true; } return false; } }; bool G1STWIsAliveClosure::do_object_b(oop p) { // An object is reachable if it is outside the collection set, // or is inside and copied. return !_g1->obj_in_cs(p) || p->is_forwarded(); } // Non Copying Keep Alive closure class G1KeepAliveClosure: public OopClosure { G1CollectedHeap* _g1; public: G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } void do_oop( oop* p) { oop obj = *p; if (_g1->obj_in_cs(obj)) { assert( obj->is_forwarded(), "invariant" ); *p = obj->forwardee(); } } }; // Copying Keep Alive closure - can be called from both // serial and parallel code as long as different worker // threads utilize different G1ParScanThreadState instances // and different queues. class G1CopyingKeepAliveClosure: public OopClosure { G1CollectedHeap* _g1h; OopClosure* _copy_non_heap_obj_cl; OopsInHeapRegionClosure* _copy_metadata_obj_cl; G1ParScanThreadState* _par_scan_state; public: G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, OopClosure* non_heap_obj_cl, OopsInHeapRegionClosure* metadata_obj_cl, G1ParScanThreadState* pss): _g1h(g1h), _copy_non_heap_obj_cl(non_heap_obj_cl), _copy_metadata_obj_cl(metadata_obj_cl), _par_scan_state(pss) {} virtual void do_oop(narrowOop* p) { do_oop_work(p); } virtual void do_oop( oop* p) { do_oop_work(p); } template void do_oop_work(T* p) { oop obj = oopDesc::load_decode_heap_oop(p); if (_g1h->obj_in_cs(obj)) { // If the referent object has been forwarded (either copied // to a new location or to itself in the event of an // evacuation failure) then we need to update the reference // field and, if both reference and referent are in the G1 // heap, update the RSet for the referent. // // If the referent has not been forwarded then we have to keep // it alive by policy. Therefore we have copy the referent. // // If the reference field is in the G1 heap then we can push // on the PSS queue. When the queue is drained (after each // phase of reference processing) the object and it's followers // will be copied, the reference field set to point to the // new location, and the RSet updated. Otherwise we need to // use the the non-heap or metadata closures directly to copy // the refernt object and update the pointer, while avoiding // updating the RSet. if (_g1h->is_in_g1_reserved(p)) { _par_scan_state->push_on_queue(p); } else { assert(!ClassLoaderDataGraph::contains((address)p), err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " PTR_FORMAT, p)); _copy_non_heap_obj_cl->do_oop(p); } } } }; // Serial drain queue closure. Called as the 'complete_gc' // closure for each discovered list in some of the // reference processing phases. class G1STWDrainQueueClosure: public VoidClosure { protected: G1CollectedHeap* _g1h; G1ParScanThreadState* _par_scan_state; G1ParScanThreadState* par_scan_state() { return _par_scan_state; } public: G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : _g1h(g1h), _par_scan_state(pss) { } void do_void() { G1ParScanThreadState* const pss = par_scan_state(); pss->trim_queue(); } }; // Parallel Reference Processing closures // Implementation of AbstractRefProcTaskExecutor for parallel reference // processing during G1 evacuation pauses. class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { private: G1CollectedHeap* _g1h; RefToScanQueueSet* _queues; FlexibleWorkGang* _workers; int _active_workers; public: G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, FlexibleWorkGang* workers, RefToScanQueueSet *task_queues, int n_workers) : _g1h(g1h), _queues(task_queues), _workers(workers), _active_workers(n_workers) { assert(n_workers > 0, "shouldn't call this otherwise"); } // Executes the given task using concurrent marking worker threads. virtual void execute(ProcessTask& task); virtual void execute(EnqueueTask& task); }; // Gang task for possibly parallel reference processing class G1STWRefProcTaskProxy: public AbstractGangTask { typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; ProcessTask& _proc_task; G1CollectedHeap* _g1h; RefToScanQueueSet *_task_queues; ParallelTaskTerminator* _terminator; public: G1STWRefProcTaskProxy(ProcessTask& proc_task, G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, ParallelTaskTerminator* terminator) : AbstractGangTask("Process reference objects in parallel"), _proc_task(proc_task), _g1h(g1h), _task_queues(task_queues), _terminator(terminator) {} virtual void work(uint worker_id) { // The reference processing task executed by a single worker. ResourceMark rm; HandleMark hm; G1STWIsAliveClosure is_alive(_g1h); G1ParScanThreadState pss(_g1h, worker_id); G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); pss.set_evac_closure(&scan_evac_cl); pss.set_evac_failure_closure(&evac_failure_cl); pss.set_partial_scan_closure(&partial_scan_cl); G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; if (_g1h->g1_policy()->during_initial_mark_pause()) { // We also need to mark copied objects. copy_non_heap_cl = ©_mark_non_heap_cl; copy_metadata_cl = ©_mark_metadata_cl; } // Keep alive closure. G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); // Complete GC closure G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); // Call the reference processing task's work routine. _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); // Note we cannot assert that the refs array is empty here as not all // of the processing tasks (specifically phase2 - pp2_work) execute // the complete_gc closure (which ordinarily would drain the queue) so // the queue may not be empty. } }; // Driver routine for parallel reference processing. // Creates an instance of the ref processing gang // task and has the worker threads execute it. void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { assert(_workers != NULL, "Need parallel worker threads."); ParallelTaskTerminator terminator(_active_workers, _queues); G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); _g1h->set_par_threads(_active_workers); _workers->run_task(&proc_task_proxy); _g1h->set_par_threads(0); } // Gang task for parallel reference enqueueing. class G1STWRefEnqueueTaskProxy: public AbstractGangTask { typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; EnqueueTask& _enq_task; public: G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : AbstractGangTask("Enqueue reference objects in parallel"), _enq_task(enq_task) { } virtual void work(uint worker_id) { _enq_task.work(worker_id); } }; // Driver routine for parallel reference enqueing. // Creates an instance of the ref enqueueing gang // task and has the worker threads execute it. void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { assert(_workers != NULL, "Need parallel worker threads."); G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); _g1h->set_par_threads(_active_workers); _workers->run_task(&enq_task_proxy); _g1h->set_par_threads(0); } // End of weak reference support closures // Abstract task used to preserve (i.e. copy) any referent objects // that are in the collection set and are pointed to by reference // objects discovered by the CM ref processor. class G1ParPreserveCMReferentsTask: public AbstractGangTask { protected: G1CollectedHeap* _g1h; RefToScanQueueSet *_queues; ParallelTaskTerminator _terminator; uint _n_workers; public: G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : AbstractGangTask("ParPreserveCMReferents"), _g1h(g1h), _queues(task_queues), _terminator(workers, _queues), _n_workers(workers) { } void work(uint worker_id) { ResourceMark rm; HandleMark hm; G1ParScanThreadState pss(_g1h, worker_id); G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); pss.set_evac_closure(&scan_evac_cl); pss.set_evac_failure_closure(&evac_failure_cl); pss.set_partial_scan_closure(&partial_scan_cl); assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; if (_g1h->g1_policy()->during_initial_mark_pause()) { // We also need to mark copied objects. copy_non_heap_cl = ©_mark_non_heap_cl; copy_metadata_cl = ©_mark_metadata_cl; } // Is alive closure G1AlwaysAliveClosure always_alive(_g1h); // Copying keep alive closure. Applied to referent objects that need // to be copied. G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); ReferenceProcessor* rp = _g1h->ref_processor_cm(); uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); uint stride = MIN2(MAX2(_n_workers, 1U), limit); // limit is set using max_num_q() - which was set using ParallelGCThreads. // So this must be true - but assert just in case someone decides to // change the worker ids. assert(0 <= worker_id && worker_id < limit, "sanity"); assert(!rp->discovery_is_atomic(), "check this code"); // Select discovered lists [i, i+stride, i+2*stride,...,limit) for (uint idx = worker_id; idx < limit; idx += stride) { DiscoveredList& ref_list = rp->discovered_refs()[idx]; DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); while (iter.has_next()) { // Since discovery is not atomic for the CM ref processor, we // can see some null referent objects. iter.load_ptrs(DEBUG_ONLY(true)); oop ref = iter.obj(); // This will filter nulls. if (iter.is_referent_alive()) { iter.make_referent_alive(); } iter.move_to_next(); } } // Drain the queue - which may cause stealing G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); drain_queue.do_void(); // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure assert(pss.refs()->is_empty(), "should be"); } }; // Weak Reference processing during an evacuation pause (part 1). void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { double ref_proc_start = os::elapsedTime(); ReferenceProcessor* rp = _ref_processor_stw; assert(rp->discovery_enabled(), "should have been enabled"); // Any reference objects, in the collection set, that were 'discovered' // by the CM ref processor should have already been copied (either by // applying the external root copy closure to the discovered lists, or // by following an RSet entry). // // But some of the referents, that are in the collection set, that these // reference objects point to may not have been copied: the STW ref // processor would have seen that the reference object had already // been 'discovered' and would have skipped discovering the reference, // but would not have treated the reference object as a regular oop. // As a reult the copy closure would not have been applied to the // referent object. // // We need to explicitly copy these referent objects - the references // will be processed at the end of remarking. // // We also need to do this copying before we process the reference // objects discovered by the STW ref processor in case one of these // referents points to another object which is also referenced by an // object discovered by the STW ref processor. assert(!G1CollectedHeap::use_parallel_gc_threads() || no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers"); set_par_threads(no_of_gc_workers); G1ParPreserveCMReferentsTask keep_cm_referents(this, no_of_gc_workers, _task_queues); if (G1CollectedHeap::use_parallel_gc_threads()) { workers()->run_task(&keep_cm_referents); } else { keep_cm_referents.work(0); } set_par_threads(0); // Closure to test whether a referent is alive. G1STWIsAliveClosure is_alive(this); // Even when parallel reference processing is enabled, the processing // of JNI refs is serial and performed serially by the current thread // rather than by a worker. The following PSS will be used for processing // JNI refs. // Use only a single queue for this PSS. G1ParScanThreadState pss(this, 0); // We do not embed a reference processor in the copying/scanning // closures while we're actually processing the discovered // reference objects. G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL); G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL); pss.set_evac_closure(&scan_evac_cl); pss.set_evac_failure_closure(&evac_failure_cl); pss.set_partial_scan_closure(&partial_scan_cl); assert(pss.refs()->is_empty(), "pre-condition"); G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; if (_g1h->g1_policy()->during_initial_mark_pause()) { // We also need to mark copied objects. copy_non_heap_cl = ©_mark_non_heap_cl; copy_metadata_cl = ©_mark_metadata_cl; } // Keep alive closure. G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); // Serial Complete GC closure G1STWDrainQueueClosure drain_queue(this, &pss); // Setup the soft refs policy... rp->setup_policy(false); if (!rp->processing_is_mt()) { // Serial reference processing... rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, NULL); } else { // Parallel reference processing assert(rp->num_q() == no_of_gc_workers, "sanity"); assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor); } // We have completed copying any necessary live referent objects // (that were not copied during the actual pause) so we can // retire any active alloc buffers pss.retire_alloc_buffers(); assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); double ref_proc_time = os::elapsedTime() - ref_proc_start; g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); } // Weak Reference processing during an evacuation pause (part 2). void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { double ref_enq_start = os::elapsedTime(); ReferenceProcessor* rp = _ref_processor_stw; assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); // Now enqueue any remaining on the discovered lists on to // the pending list. if (!rp->processing_is_mt()) { // Serial reference processing... rp->enqueue_discovered_references(); } else { // Parallel reference enqueuing assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active workers"); assert(rp->num_q() == no_of_gc_workers, "sanity"); assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); rp->enqueue_discovered_references(&par_task_executor); } rp->verify_no_references_recorded(); assert(!rp->discovery_enabled(), "should have been disabled"); // FIXME // CM's reference processing also cleans up the string and symbol tables. // Should we do that here also? We could, but it is a serial operation // and could signicantly increase the pause time. double ref_enq_time = os::elapsedTime() - ref_enq_start; g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); } void G1CollectedHeap::evacuate_collection_set() { _expand_heap_after_alloc_failure = true; set_evacuation_failed(false); // Should G1EvacuationFailureALot be in effect for this GC? NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) g1_rem_set()->prepare_for_oops_into_collection_set_do(); concurrent_g1_refine()->set_use_cache(false); concurrent_g1_refine()->clear_hot_cache_claimed_index(); uint n_workers; if (G1CollectedHeap::use_parallel_gc_threads()) { n_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), workers()->active_workers(), Threads::number_of_non_daemon_threads()); assert(UseDynamicNumberOfGCThreads || n_workers == workers()->total_workers(), "If not dynamic should be using all the workers"); workers()->set_active_workers(n_workers); set_par_threads(n_workers); } else { assert(n_par_threads() == 0, "Should be the original non-parallel value"); n_workers = 1; } G1ParTask g1_par_task(this, _task_queues); init_for_evac_failure(NULL); rem_set()->prepare_for_younger_refs_iterate(true); assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); double start_par_time_sec = os::elapsedTime(); double end_par_time_sec; { StrongRootsScope srs(this); if (G1CollectedHeap::use_parallel_gc_threads()) { // The individual threads will set their evac-failure closures. if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); // These tasks use ShareHeap::_process_strong_tasks assert(UseDynamicNumberOfGCThreads || workers()->active_workers() == workers()->total_workers(), "If not dynamic should be using all the workers"); workers()->run_task(&g1_par_task); } else { g1_par_task.set_for_termination(n_workers); g1_par_task.work(0); } end_par_time_sec = os::elapsedTime(); // Closing the inner scope will execute the destructor // for the StrongRootsScope object. We record the current // elapsed time before closing the scope so that time // taken for the SRS destructor is NOT included in the // reported parallel time. } double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; g1_policy()->phase_times()->record_par_time(par_time_ms); double code_root_fixup_time_ms = (os::elapsedTime() - end_par_time_sec) * 1000.0; g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); set_par_threads(0); // Process any discovered reference objects - we have // to do this _before_ we retire the GC alloc regions // as we may have to copy some 'reachable' referent // objects (and their reachable sub-graphs) that were // not copied during the pause. process_discovered_references(n_workers); // Weak root processing. // Note: when JSR 292 is enabled and code blobs can contain // non-perm oops then we will need to process the code blobs // here too. { G1STWIsAliveClosure is_alive(this); G1KeepAliveClosure keep_alive(this); JNIHandles::weak_oops_do(&is_alive, &keep_alive); } release_gc_alloc_regions(n_workers); g1_rem_set()->cleanup_after_oops_into_collection_set_do(); concurrent_g1_refine()->clear_hot_cache(); concurrent_g1_refine()->set_use_cache(true); finalize_for_evac_failure(); if (evacuation_failed()) { remove_self_forwarding_pointers(); // Reset the G1EvacuationFailureALot counters and flags // Note: the values are reset only when an actual // evacuation failure occurs. NOT_PRODUCT(reset_evacuation_should_fail();) } // Enqueue any remaining references remaining on the STW // reference processor's discovered lists. We need to do // this after the card table is cleaned (and verified) as // the act of enqueuing entries on to the pending list // will log these updates (and dirty their associated // cards). We need these updates logged to update any // RSets. enqueue_discovered_references(n_workers); if (G1DeferredRSUpdate) { RedirtyLoggedCardTableEntryFastClosure redirty; dirty_card_queue_set().set_closure(&redirty); dirty_card_queue_set().apply_closure_to_all_completed_buffers(); DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); dcq.merge_bufferlists(&dirty_card_queue_set()); assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); } COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); } void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, size_t* pre_used, FreeRegionList* free_list, OldRegionSet* old_proxy_set, HumongousRegionSet* humongous_proxy_set, HRRSCleanupTask* hrrs_cleanup_task, bool par) { if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { if (hr->isHumongous()) { assert(hr->startsHumongous(), "we should only see starts humongous"); free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); } else { _old_set.remove_with_proxy(hr, old_proxy_set); free_region(hr, pre_used, free_list, par); } } else { hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); } } void G1CollectedHeap::free_region(HeapRegion* hr, size_t* pre_used, FreeRegionList* free_list, bool par) { assert(!hr->isHumongous(), "this is only for non-humongous regions"); assert(!hr->is_empty(), "the region should not be empty"); assert(free_list != NULL, "pre-condition"); *pre_used += hr->used(); hr->hr_clear(par, true /* clear_space */); free_list->add_as_head(hr); } void G1CollectedHeap::free_humongous_region(HeapRegion* hr, size_t* pre_used, FreeRegionList* free_list, HumongousRegionSet* humongous_proxy_set, bool par) { assert(hr->startsHumongous(), "this is only for starts humongous regions"); assert(free_list != NULL, "pre-condition"); assert(humongous_proxy_set != NULL, "pre-condition"); size_t hr_used = hr->used(); size_t hr_capacity = hr->capacity(); size_t hr_pre_used = 0; _humongous_set.remove_with_proxy(hr, humongous_proxy_set); // We need to read this before we make the region non-humongous, // otherwise the information will be gone. uint last_index = hr->last_hc_index(); hr->set_notHumongous(); free_region(hr, &hr_pre_used, free_list, par); uint i = hr->hrs_index() + 1; while (i < last_index) { HeapRegion* curr_hr = region_at(i); assert(curr_hr->continuesHumongous(), "invariant"); curr_hr->set_notHumongous(); free_region(curr_hr, &hr_pre_used, free_list, par); i += 1; } assert(hr_pre_used == hr_used, err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " "should be the same", hr_pre_used, hr_used)); *pre_used += hr_pre_used; } void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, FreeRegionList* free_list, OldRegionSet* old_proxy_set, HumongousRegionSet* humongous_proxy_set, bool par) { if (pre_used > 0) { Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); assert(_summary_bytes_used >= pre_used, err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " "should be >= pre_used: "SIZE_FORMAT, _summary_bytes_used, pre_used)); _summary_bytes_used -= pre_used; } if (free_list != NULL && !free_list->is_empty()) { MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); _free_list.add_as_head(free_list); } if (old_proxy_set != NULL && !old_proxy_set->is_empty()) { MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); _old_set.update_from_proxy(old_proxy_set); } if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); _humongous_set.update_from_proxy(humongous_proxy_set); } } class G1ParCleanupCTTask : public AbstractGangTask { CardTableModRefBS* _ct_bs; G1CollectedHeap* _g1h; HeapRegion* volatile _su_head; public: G1ParCleanupCTTask(CardTableModRefBS* ct_bs, G1CollectedHeap* g1h) : AbstractGangTask("G1 Par Cleanup CT Task"), _ct_bs(ct_bs), _g1h(g1h) { } void work(uint worker_id) { HeapRegion* r; while (r = _g1h->pop_dirty_cards_region()) { clear_cards(r); } } void clear_cards(HeapRegion* r) { // Cards of the survivors should have already been dirtied. if (!r->is_survivor()) { _ct_bs->clear(MemRegion(r->bottom(), r->end())); } } }; #ifndef PRODUCT class G1VerifyCardTableCleanup: public HeapRegionClosure { G1CollectedHeap* _g1h; CardTableModRefBS* _ct_bs; public: G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) : _g1h(g1h), _ct_bs(ct_bs) { } virtual bool doHeapRegion(HeapRegion* r) { if (r->is_survivor()) { _g1h->verify_dirty_region(r); } else { _g1h->verify_not_dirty_region(r); } return false; } }; void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { // All of the region should be clean. CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); MemRegion mr(hr->bottom(), hr->end()); ct_bs->verify_not_dirty_region(mr); } void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { // We cannot guarantee that [bottom(),end()] is dirty. Threads // dirty allocated blocks as they allocate them. The thread that // retires each region and replaces it with a new one will do a // maximal allocation to fill in [pre_dummy_top(),end()] but will // not dirty that area (one less thing to have to do while holding // a lock). So we can only verify that [bottom(),pre_dummy_top()] // is dirty. CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); MemRegion mr(hr->bottom(), hr->pre_dummy_top()); ct_bs->verify_dirty_region(mr); } void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { verify_dirty_region(hr); } } void G1CollectedHeap::verify_dirty_young_regions() { verify_dirty_young_list(_young_list->first_region()); } #endif void G1CollectedHeap::cleanUpCardTable() { CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); double start = os::elapsedTime(); { // Iterate over the dirty cards region list. G1ParCleanupCTTask cleanup_task(ct_bs, this); if (G1CollectedHeap::use_parallel_gc_threads()) { set_par_threads(); workers()->run_task(&cleanup_task); set_par_threads(0); } else { while (_dirty_cards_region_list) { HeapRegion* r = _dirty_cards_region_list; cleanup_task.clear_cards(r); _dirty_cards_region_list = r->get_next_dirty_cards_region(); if (_dirty_cards_region_list == r) { // The last region. _dirty_cards_region_list = NULL; } r->set_next_dirty_cards_region(NULL); } } #ifndef PRODUCT if (G1VerifyCTCleanup || VerifyAfterGC) { G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); heap_region_iterate(&cleanup_verifier); } #endif } double elapsed = os::elapsedTime() - start; g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); } void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { size_t pre_used = 0; FreeRegionList local_free_list("Local List for CSet Freeing"); double young_time_ms = 0.0; double non_young_time_ms = 0.0; // Since the collection set is a superset of the the young list, // all we need to do to clear the young list is clear its // head and length, and unlink any young regions in the code below _young_list->clear(); G1CollectorPolicy* policy = g1_policy(); double start_sec = os::elapsedTime(); bool non_young = true; HeapRegion* cur = cs_head; int age_bound = -1; size_t rs_lengths = 0; while (cur != NULL) { assert(!is_on_master_free_list(cur), "sanity"); if (non_young) { if (cur->is_young()) { double end_sec = os::elapsedTime(); double elapsed_ms = (end_sec - start_sec) * 1000.0; non_young_time_ms += elapsed_ms; start_sec = os::elapsedTime(); non_young = false; } } else { if (!cur->is_young()) { double end_sec = os::elapsedTime(); double elapsed_ms = (end_sec - start_sec) * 1000.0; young_time_ms += elapsed_ms; start_sec = os::elapsedTime(); non_young = true; } } rs_lengths += cur->rem_set()->occupied(); HeapRegion* next = cur->next_in_collection_set(); assert(cur->in_collection_set(), "bad CS"); cur->set_next_in_collection_set(NULL); cur->set_in_collection_set(false); if (cur->is_young()) { int index = cur->young_index_in_cset(); assert(index != -1, "invariant"); assert((uint) index < policy->young_cset_region_length(), "invariant"); size_t words_survived = _surviving_young_words[index]; cur->record_surv_words_in_group(words_survived); // At this point the we have 'popped' cur from the collection set // (linked via next_in_collection_set()) but it is still in the // young list (linked via next_young_region()). Clear the // _next_young_region field. cur->set_next_young_region(NULL); } else { int index = cur->young_index_in_cset(); assert(index == -1, "invariant"); } assert( (cur->is_young() && cur->young_index_in_cset() > -1) || (!cur->is_young() && cur->young_index_in_cset() == -1), "invariant" ); if (!cur->evacuation_failed()) { MemRegion used_mr = cur->used_region(); // And the region is empty. assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); free_region(cur, &pre_used, &local_free_list, false /* par */); } else { cur->uninstall_surv_rate_group(); if (cur->is_young()) { cur->set_young_index_in_cset(-1); } cur->set_not_young(); cur->set_evacuation_failed(false); // The region is now considered to be old. _old_set.add(cur); } cur = next; } policy->record_max_rs_lengths(rs_lengths); policy->cset_regions_freed(); double end_sec = os::elapsedTime(); double elapsed_ms = (end_sec - start_sec) * 1000.0; if (non_young) { non_young_time_ms += elapsed_ms; } else { young_time_ms += elapsed_ms; } update_sets_after_freeing_regions(pre_used, &local_free_list, NULL /* old_proxy_set */, NULL /* humongous_proxy_set */, false /* par */); policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); } // This routine is similar to the above but does not record // any policy statistics or update free lists; we are abandoning // the current incremental collection set in preparation of a // full collection. After the full GC we will start to build up // the incremental collection set again. // This is only called when we're doing a full collection // and is immediately followed by the tearing down of the young list. void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { HeapRegion* cur = cs_head; while (cur != NULL) { HeapRegion* next = cur->next_in_collection_set(); assert(cur->in_collection_set(), "bad CS"); cur->set_next_in_collection_set(NULL); cur->set_in_collection_set(false); cur->set_young_index_in_cset(-1); cur = next; } } void G1CollectedHeap::set_free_regions_coming() { if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " "setting free regions coming"); } assert(!free_regions_coming(), "pre-condition"); _free_regions_coming = true; } void G1CollectedHeap::reset_free_regions_coming() { assert(free_regions_coming(), "pre-condition"); { MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); _free_regions_coming = false; SecondaryFreeList_lock->notify_all(); } if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " "reset free regions coming"); } } void G1CollectedHeap::wait_while_free_regions_coming() { // Most of the time we won't have to wait, so let's do a quick test // first before we take the lock. if (!free_regions_coming()) { return; } if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " "waiting for free regions"); } { MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); while (free_regions_coming()) { SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); } } if (G1ConcRegionFreeingVerbose) { gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " "done waiting for free regions"); } } void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { assert(heap_lock_held_for_gc(), "the heap lock should already be held by or for this thread"); _young_list->push_region(hr); } class NoYoungRegionsClosure: public HeapRegionClosure { private: bool _success; public: NoYoungRegionsClosure() : _success(true) { } bool doHeapRegion(HeapRegion* r) { if (r->is_young()) { gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", r->bottom(), r->end()); _success = false; } return false; } bool success() { return _success; } }; bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { bool ret = _young_list->check_list_empty(check_sample); if (check_heap) { NoYoungRegionsClosure closure; heap_region_iterate(&closure); ret = ret && closure.success(); } return ret; } class TearDownRegionSetsClosure : public HeapRegionClosure { private: OldRegionSet *_old_set; public: TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { } bool doHeapRegion(HeapRegion* r) { if (r->is_empty()) { // We ignore empty regions, we'll empty the free list afterwards } else if (r->is_young()) { // We ignore young regions, we'll empty the young list afterwards } else if (r->isHumongous()) { // We ignore humongous regions, we're not tearing down the // humongous region set } else { // The rest should be old _old_set->remove(r); } return false; } ~TearDownRegionSetsClosure() { assert(_old_set->is_empty(), "post-condition"); } }; void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { assert_at_safepoint(true /* should_be_vm_thread */); if (!free_list_only) { TearDownRegionSetsClosure cl(&_old_set); heap_region_iterate(&cl); // Need to do this after the heap iteration to be able to // recognize the young regions and ignore them during the iteration. _young_list->empty_list(); } _free_list.remove_all(); } class RebuildRegionSetsClosure : public HeapRegionClosure { private: bool _free_list_only; OldRegionSet* _old_set; FreeRegionList* _free_list; size_t _total_used; public: RebuildRegionSetsClosure(bool free_list_only, OldRegionSet* old_set, FreeRegionList* free_list) : _free_list_only(free_list_only), _old_set(old_set), _free_list(free_list), _total_used(0) { assert(_free_list->is_empty(), "pre-condition"); if (!free_list_only) { assert(_old_set->is_empty(), "pre-condition"); } } bool doHeapRegion(HeapRegion* r) { if (r->continuesHumongous()) { return false; } if (r->is_empty()) { // Add free regions to the free list _free_list->add_as_tail(r); } else if (!_free_list_only) { assert(!r->is_young(), "we should not come across young regions"); if (r->isHumongous()) { // We ignore humongous regions, we left the humongous set unchanged } else { // The rest should be old, add them to the old set _old_set->add(r); } _total_used += r->used(); } return false; } size_t total_used() { return _total_used; } }; void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { assert_at_safepoint(true /* should_be_vm_thread */); RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); heap_region_iterate(&cl); if (!free_list_only) { _summary_bytes_used = cl.total_used(); } assert(_summary_bytes_used == recalculate_used(), err_msg("inconsistent _summary_bytes_used, " "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, _summary_bytes_used, recalculate_used())); } void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { _refine_cte_cl->set_concurrent(concurrent); } bool G1CollectedHeap::is_in_closed_subset(const void* p) const { HeapRegion* hr = heap_region_containing(p); if (hr == NULL) { return false; } else { return hr->is_in(p); } } // Methods for the mutator alloc region HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, bool force) { assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); assert(!force || g1_policy()->can_expand_young_list(), "if force is true we should be able to expand the young list"); bool young_list_full = g1_policy()->is_young_list_full(); if (force || !young_list_full) { HeapRegion* new_alloc_region = new_region(word_size, false /* do_expand */); if (new_alloc_region != NULL) { set_region_short_lived_locked(new_alloc_region); _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); return new_alloc_region; } } return NULL; } void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, size_t allocated_bytes) { assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); assert(alloc_region->is_young(), "all mutator alloc regions should be young"); g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); _summary_bytes_used += allocated_bytes; _hr_printer.retire(alloc_region); // We update the eden sizes here, when the region is retired, // instead of when it's allocated, since this is the point that its // used space has been recored in _summary_bytes_used. g1mm()->update_eden_size(); } HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, bool force) { return _g1h->new_mutator_alloc_region(word_size, force); } void G1CollectedHeap::set_par_threads() { // Don't change the number of workers. Use the value previously set // in the workgroup. assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); uint n_workers = workers()->active_workers(); assert(UseDynamicNumberOfGCThreads || n_workers == workers()->total_workers(), "Otherwise should be using the total number of workers"); if (n_workers == 0) { assert(false, "Should have been set in prior evacuation pause."); n_workers = ParallelGCThreads; workers()->set_active_workers(n_workers); } set_par_threads(n_workers); } void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, size_t allocated_bytes) { _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); } // Methods for the GC alloc regions HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, uint count, GCAllocPurpose ap) { assert(FreeList_lock->owned_by_self(), "pre-condition"); if (count < g1_policy()->max_regions(ap)) { HeapRegion* new_alloc_region = new_region(word_size, true /* do_expand */); if (new_alloc_region != NULL) { // We really only need to do this for old regions given that we // should never scan survivors. But it doesn't hurt to do it // for survivors too. new_alloc_region->set_saved_mark(); if (ap == GCAllocForSurvived) { new_alloc_region->set_survivor(); _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); } else { _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); } bool during_im = g1_policy()->during_initial_mark_pause(); new_alloc_region->note_start_of_copying(during_im); return new_alloc_region; } else { g1_policy()->note_alloc_region_limit_reached(ap); } } return NULL; } void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, size_t allocated_bytes, GCAllocPurpose ap) { bool during_im = g1_policy()->during_initial_mark_pause(); alloc_region->note_end_of_copying(during_im); g1_policy()->record_bytes_copied_during_gc(allocated_bytes); if (ap == GCAllocForSurvived) { young_list()->add_survivor_region(alloc_region); } else { _old_set.add(alloc_region); } _hr_printer.retire(alloc_region); } HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, bool force) { assert(!force, "not supported for GC alloc regions"); return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); } void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, size_t allocated_bytes) { _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, GCAllocForSurvived); } HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, bool force) { assert(!force, "not supported for GC alloc regions"); return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); } void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, size_t allocated_bytes) { _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, GCAllocForTenured); } // Heap region set verification class VerifyRegionListsClosure : public HeapRegionClosure { private: FreeRegionList* _free_list; OldRegionSet* _old_set; HumongousRegionSet* _humongous_set; uint _region_count; public: VerifyRegionListsClosure(OldRegionSet* old_set, HumongousRegionSet* humongous_set, FreeRegionList* free_list) : _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list), _region_count(0) { } uint region_count() { return _region_count; } bool doHeapRegion(HeapRegion* hr) { _region_count += 1; if (hr->continuesHumongous()) { return false; } if (hr->is_young()) { // TODO } else if (hr->startsHumongous()) { _humongous_set->verify_next_region(hr); } else if (hr->is_empty()) { _free_list->verify_next_region(hr); } else { _old_set->verify_next_region(hr); } return false; } }; HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, HeapWord* bottom) { HeapWord* end = bottom + HeapRegion::GrainWords; MemRegion mr(bottom, end); assert(_g1_reserved.contains(mr), "invariant"); // This might return NULL if the allocation fails return new HeapRegion(hrs_index, _bot_shared, mr); } void G1CollectedHeap::verify_region_sets() { assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); // First, check the explicit lists. _free_list.verify(); { // Given that a concurrent operation might be adding regions to // the secondary free list we have to take the lock before // verifying it. MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); _secondary_free_list.verify(); } _old_set.verify(); _humongous_set.verify(); // If a concurrent region freeing operation is in progress it will // be difficult to correctly attributed any free regions we come // across to the correct free list given that they might belong to // one of several (free_list, secondary_free_list, any local lists, // etc.). So, if that's the case we will skip the rest of the // verification operation. Alternatively, waiting for the concurrent // operation to complete will have a non-trivial effect on the GC's // operation (no concurrent operation will last longer than the // interval between two calls to verification) and it might hide // any issues that we would like to catch during testing. if (free_regions_coming()) { return; } // Make sure we append the secondary_free_list on the free_list so // that all free regions we will come across can be safely // attributed to the free_list. append_secondary_free_list_if_not_empty_with_lock(); // Finally, make sure that the region accounting in the lists is // consistent with what we see in the heap. _old_set.verify_start(); _humongous_set.verify_start(); _free_list.verify_start(); VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); heap_region_iterate(&cl); _old_set.verify_end(); _humongous_set.verify_end(); _free_list.verify_end(); }