/* * Copyright (c) 2005, 2014, 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 "classfile/symbolTable.hpp" #include "classfile/systemDictionary.hpp" #include "code/codeCache.hpp" #include "gc_implementation/parallelScavenge/gcTaskManager.hpp" #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp" #include "gc_implementation/parallelScavenge/pcTasks.hpp" #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp" #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp" #include "gc_implementation/parallelScavenge/psMarkSweep.hpp" #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp" #include "gc_implementation/parallelScavenge/psOldGen.hpp" #include "gc_implementation/parallelScavenge/psParallelCompact.hpp" #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp" #include "gc_implementation/parallelScavenge/psScavenge.hpp" #include "gc_implementation/parallelScavenge/psYoungGen.hpp" #include "gc_implementation/shared/gcHeapSummary.hpp" #include "gc_implementation/shared/gcTimer.hpp" #include "gc_implementation/shared/gcTrace.hpp" #include "gc_implementation/shared/gcTraceTime.hpp" #include "gc_implementation/shared/isGCActiveMark.hpp" #include "gc_interface/gcCause.hpp" #include "memory/gcLocker.inline.hpp" #include "memory/referencePolicy.hpp" #include "memory/referenceProcessor.hpp" #include "oops/methodData.hpp" #include "oops/oop.inline.hpp" #include "oops/oop.pcgc.inline.hpp" #include "runtime/fprofiler.hpp" #include "runtime/safepoint.hpp" #include "runtime/vmThread.hpp" #include "services/management.hpp" #include "services/memoryService.hpp" #include "services/memTracker.hpp" #include "utilities/events.hpp" #include "utilities/stack.inline.hpp" #include PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC // All sizes are in HeapWords. const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize; const size_t ParallelCompactData::RegionSizeBytes = RegionSize << LogHeapWordSize; const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1; const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1; const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask; const size_t ParallelCompactData::Log2BlockSize = 7; // 128 words const size_t ParallelCompactData::BlockSize = (size_t)1 << Log2BlockSize; const size_t ParallelCompactData::BlockSizeBytes = BlockSize << LogHeapWordSize; const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1; const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1; const size_t ParallelCompactData::BlockAddrMask = ~BlockAddrOffsetMask; const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize; const size_t ParallelCompactData::Log2BlocksPerRegion = Log2RegionSize - Log2BlockSize; const ParallelCompactData::RegionData::region_sz_t ParallelCompactData::RegionData::dc_shift = 27; const ParallelCompactData::RegionData::region_sz_t ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift; const ParallelCompactData::RegionData::region_sz_t ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift; const ParallelCompactData::RegionData::region_sz_t ParallelCompactData::RegionData::los_mask = ~dc_mask; const ParallelCompactData::RegionData::region_sz_t ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift; const ParallelCompactData::RegionData::region_sz_t ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift; SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id]; bool PSParallelCompact::_print_phases = false; ReferenceProcessor* PSParallelCompact::_ref_processor = NULL; Klass* PSParallelCompact::_updated_int_array_klass_obj = NULL; double PSParallelCompact::_dwl_mean; double PSParallelCompact::_dwl_std_dev; double PSParallelCompact::_dwl_first_term; double PSParallelCompact::_dwl_adjustment; #ifdef ASSERT bool PSParallelCompact::_dwl_initialized = false; #endif // #ifdef ASSERT void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size, HeapWord* destination) { assert(src_region_idx != 0, "invalid src_region_idx"); assert(partial_obj_size != 0, "invalid partial_obj_size argument"); assert(destination != NULL, "invalid destination argument"); _src_region_idx = src_region_idx; _partial_obj_size = partial_obj_size; _destination = destination; // These fields may not be updated below, so make sure they're clear. assert(_dest_region_addr == NULL, "should have been cleared"); assert(_first_src_addr == NULL, "should have been cleared"); // Determine the number of destination regions for the partial object. HeapWord* const last_word = destination + partial_obj_size - 1; const ParallelCompactData& sd = PSParallelCompact::summary_data(); HeapWord* const beg_region_addr = sd.region_align_down(destination); HeapWord* const end_region_addr = sd.region_align_down(last_word); if (beg_region_addr == end_region_addr) { // One destination region. _destination_count = 1; if (end_region_addr == destination) { // The destination falls on a region boundary, thus the first word of the // partial object will be the first word copied to the destination region. _dest_region_addr = end_region_addr; _first_src_addr = sd.region_to_addr(src_region_idx); } } else { // Two destination regions. When copied, the partial object will cross a // destination region boundary, so a word somewhere within the partial // object will be the first word copied to the second destination region. _destination_count = 2; _dest_region_addr = end_region_addr; const size_t ofs = pointer_delta(end_region_addr, destination); assert(ofs < _partial_obj_size, "sanity"); _first_src_addr = sd.region_to_addr(src_region_idx) + ofs; } } void SplitInfo::clear() { _src_region_idx = 0; _partial_obj_size = 0; _destination = NULL; _destination_count = 0; _dest_region_addr = NULL; _first_src_addr = NULL; assert(!is_valid(), "sanity"); } #ifdef ASSERT void SplitInfo::verify_clear() { assert(_src_region_idx == 0, "not clear"); assert(_partial_obj_size == 0, "not clear"); assert(_destination == NULL, "not clear"); assert(_destination_count == 0, "not clear"); assert(_dest_region_addr == NULL, "not clear"); assert(_first_src_addr == NULL, "not clear"); } #endif // #ifdef ASSERT void PSParallelCompact::print_on_error(outputStream* st) { _mark_bitmap.print_on_error(st); } #ifndef PRODUCT const char* PSParallelCompact::space_names[] = { "old ", "eden", "from", "to " }; void PSParallelCompact::print_region_ranges() { tty->print_cr("space bottom top end new_top"); tty->print_cr("------ ---------- ---------- ---------- ----------"); for (unsigned int id = 0; id < last_space_id; ++id) { const MutableSpace* space = _space_info[id].space(); tty->print_cr("%u %s " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ", id, space_names[id], summary_data().addr_to_region_idx(space->bottom()), summary_data().addr_to_region_idx(space->top()), summary_data().addr_to_region_idx(space->end()), summary_data().addr_to_region_idx(_space_info[id].new_top())); } } void print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c) { #define REGION_IDX_FORMAT SIZE_FORMAT_W(7) #define REGION_DATA_FORMAT SIZE_FORMAT_W(5) ParallelCompactData& sd = PSParallelCompact::summary_data(); size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0; tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " " REGION_IDX_FORMAT " " PTR_FORMAT " " REGION_DATA_FORMAT " " REGION_DATA_FORMAT " " REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d", i, c->data_location(), dci, c->destination(), c->partial_obj_size(), c->live_obj_size(), c->data_size(), c->source_region(), c->destination_count()); #undef REGION_IDX_FORMAT #undef REGION_DATA_FORMAT } void print_generic_summary_data(ParallelCompactData& summary_data, HeapWord* const beg_addr, HeapWord* const end_addr) { size_t total_words = 0; size_t i = summary_data.addr_to_region_idx(beg_addr); const size_t last = summary_data.addr_to_region_idx(end_addr); HeapWord* pdest = 0; while (i <= last) { ParallelCompactData::RegionData* c = summary_data.region(i); if (c->data_size() != 0 || c->destination() != pdest) { print_generic_summary_region(i, c); total_words += c->data_size(); pdest = c->destination(); } ++i; } tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize); } void print_generic_summary_data(ParallelCompactData& summary_data, SpaceInfo* space_info) { for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) { const MutableSpace* space = space_info[id].space(); print_generic_summary_data(summary_data, space->bottom(), MAX2(space->top(), space_info[id].new_top())); } } void print_initial_summary_region(size_t i, const ParallelCompactData::RegionData* c, bool newline = true) { tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d", i, c->destination(), c->partial_obj_size(), c->live_obj_size(), c->data_size(), c->source_region(), c->destination_count()); if (newline) tty->cr(); } void print_initial_summary_data(ParallelCompactData& summary_data, const MutableSpace* space) { if (space->top() == space->bottom()) { return; } const size_t region_size = ParallelCompactData::RegionSize; typedef ParallelCompactData::RegionData RegionData; HeapWord* const top_aligned_up = summary_data.region_align_up(space->top()); const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up); const RegionData* c = summary_data.region(end_region - 1); HeapWord* end_addr = c->destination() + c->data_size(); const size_t live_in_space = pointer_delta(end_addr, space->bottom()); // Print (and count) the full regions at the beginning of the space. size_t full_region_count = 0; size_t i = summary_data.addr_to_region_idx(space->bottom()); while (i < end_region && summary_data.region(i)->data_size() == region_size) { print_initial_summary_region(i, summary_data.region(i)); ++full_region_count; ++i; } size_t live_to_right = live_in_space - full_region_count * region_size; double max_reclaimed_ratio = 0.0; size_t max_reclaimed_ratio_region = 0; size_t max_dead_to_right = 0; size_t max_live_to_right = 0; // Print the 'reclaimed ratio' for regions while there is something live in // the region or to the right of it. The remaining regions are empty (and // uninteresting), and computing the ratio will result in division by 0. while (i < end_region && live_to_right > 0) { c = summary_data.region(i); HeapWord* const region_addr = summary_data.region_to_addr(i); const size_t used_to_right = pointer_delta(space->top(), region_addr); const size_t dead_to_right = used_to_right - live_to_right; const double reclaimed_ratio = double(dead_to_right) / live_to_right; if (reclaimed_ratio > max_reclaimed_ratio) { max_reclaimed_ratio = reclaimed_ratio; max_reclaimed_ratio_region = i; max_dead_to_right = dead_to_right; max_live_to_right = live_to_right; } print_initial_summary_region(i, c, false); tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10), reclaimed_ratio, dead_to_right, live_to_right); live_to_right -= c->data_size(); ++i; } // Any remaining regions are empty. Print one more if there is one. if (i < end_region) { print_initial_summary_region(i, summary_data.region(i)); } tty->print_cr("max: " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " " "l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f", max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio); } void print_initial_summary_data(ParallelCompactData& summary_data, SpaceInfo* space_info) { unsigned int id = PSParallelCompact::old_space_id; const MutableSpace* space; do { space = space_info[id].space(); print_initial_summary_data(summary_data, space); } while (++id < PSParallelCompact::eden_space_id); do { space = space_info[id].space(); print_generic_summary_data(summary_data, space->bottom(), space->top()); } while (++id < PSParallelCompact::last_space_id); } #endif // #ifndef PRODUCT #ifdef ASSERT size_t add_obj_count; size_t add_obj_size; size_t mark_bitmap_count; size_t mark_bitmap_size; #endif // #ifdef ASSERT ParallelCompactData::ParallelCompactData() { _region_start = 0; _region_vspace = 0; _reserved_byte_size = 0; _region_data = 0; _region_count = 0; _block_vspace = 0; _block_data = 0; _block_count = 0; } bool ParallelCompactData::initialize(MemRegion covered_region) { _region_start = covered_region.start(); const size_t region_size = covered_region.word_size(); DEBUG_ONLY(_region_end = _region_start + region_size;) assert(region_align_down(_region_start) == _region_start, "region start not aligned"); assert((region_size & RegionSizeOffsetMask) == 0, "region size not a multiple of RegionSize"); bool result = initialize_region_data(region_size) && initialize_block_data(); return result; } PSVirtualSpace* ParallelCompactData::create_vspace(size_t count, size_t element_size) { const size_t raw_bytes = count * element_size; const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10); const size_t granularity = os::vm_allocation_granularity(); _reserved_byte_size = align_size_up(raw_bytes, MAX2(page_sz, granularity)); const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 : MAX2(page_sz, granularity); ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0); os::trace_page_sizes("par compact", raw_bytes, raw_bytes, page_sz, rs.base(), rs.size()); MemTracker::record_virtual_memory_type((address)rs.base(), mtGC); PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz); if (vspace != 0) { if (vspace->expand_by(_reserved_byte_size)) { return vspace; } delete vspace; // Release memory reserved in the space. rs.release(); } return 0; } bool ParallelCompactData::initialize_region_data(size_t region_size) { const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize; _region_vspace = create_vspace(count, sizeof(RegionData)); if (_region_vspace != 0) { _region_data = (RegionData*)_region_vspace->reserved_low_addr(); _region_count = count; return true; } return false; } bool ParallelCompactData::initialize_block_data() { assert(_region_count != 0, "region data must be initialized first"); const size_t count = _region_count << Log2BlocksPerRegion; _block_vspace = create_vspace(count, sizeof(BlockData)); if (_block_vspace != 0) { _block_data = (BlockData*)_block_vspace->reserved_low_addr(); _block_count = count; return true; } return false; } void ParallelCompactData::clear() { memset(_region_data, 0, _region_vspace->committed_size()); memset(_block_data, 0, _block_vspace->committed_size()); } void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) { assert(beg_region <= _region_count, "beg_region out of range"); assert(end_region <= _region_count, "end_region out of range"); assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize"); const size_t region_cnt = end_region - beg_region; memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData)); const size_t beg_block = beg_region * BlocksPerRegion; const size_t block_cnt = region_cnt * BlocksPerRegion; memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData)); } HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const { const RegionData* cur_cp = region(region_idx); const RegionData* const end_cp = region(region_count() - 1); HeapWord* result = region_to_addr(region_idx); if (cur_cp < end_cp) { do { result += cur_cp->partial_obj_size(); } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp); } return result; } void ParallelCompactData::add_obj(HeapWord* addr, size_t len) { const size_t obj_ofs = pointer_delta(addr, _region_start); const size_t beg_region = obj_ofs >> Log2RegionSize; const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize; DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);) DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);) if (beg_region == end_region) { // All in one region. _region_data[beg_region].add_live_obj(len); return; } // First region. const size_t beg_ofs = region_offset(addr); _region_data[beg_region].add_live_obj(RegionSize - beg_ofs); Klass* klass = ((oop)addr)->klass(); // Middle regions--completely spanned by this object. for (size_t region = beg_region + 1; region < end_region; ++region) { _region_data[region].set_partial_obj_size(RegionSize); _region_data[region].set_partial_obj_addr(addr); } // Last region. const size_t end_ofs = region_offset(addr + len - 1); _region_data[end_region].set_partial_obj_size(end_ofs + 1); _region_data[end_region].set_partial_obj_addr(addr); } void ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end) { assert(region_offset(beg) == 0, "not RegionSize aligned"); assert(region_offset(end) == 0, "not RegionSize aligned"); size_t cur_region = addr_to_region_idx(beg); const size_t end_region = addr_to_region_idx(end); HeapWord* addr = beg; while (cur_region < end_region) { _region_data[cur_region].set_destination(addr); _region_data[cur_region].set_destination_count(0); _region_data[cur_region].set_source_region(cur_region); _region_data[cur_region].set_data_location(addr); // Update live_obj_size so the region appears completely full. size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size(); _region_data[cur_region].set_live_obj_size(live_size); ++cur_region; addr += RegionSize; } } // Find the point at which a space can be split and, if necessary, record the // split point. // // If the current src region (which overflowed the destination space) doesn't // have a partial object, the split point is at the beginning of the current src // region (an "easy" split, no extra bookkeeping required). // // If the current src region has a partial object, the split point is in the // region where that partial object starts (call it the split_region). If // split_region has a partial object, then the split point is just after that // partial object (a "hard" split where we have to record the split data and // zero the partial_obj_size field). With a "hard" split, we know that the // partial_obj ends within split_region because the partial object that caused // the overflow starts in split_region. If split_region doesn't have a partial // obj, then the split is at the beginning of split_region (another "easy" // split). HeapWord* ParallelCompactData::summarize_split_space(size_t src_region, SplitInfo& split_info, HeapWord* destination, HeapWord* target_end, HeapWord** target_next) { assert(destination <= target_end, "sanity"); assert(destination + _region_data[src_region].data_size() > target_end, "region should not fit into target space"); assert(is_region_aligned(target_end), "sanity"); size_t split_region = src_region; HeapWord* split_destination = destination; size_t partial_obj_size = _region_data[src_region].partial_obj_size(); if (destination + partial_obj_size > target_end) { // The split point is just after the partial object (if any) in the // src_region that contains the start of the object that overflowed the // destination space. // // Find the start of the "overflow" object and set split_region to the // region containing it. HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr(); split_region = addr_to_region_idx(overflow_obj); // Clear the source_region field of all destination regions whose first word // came from data after the split point (a non-null source_region field // implies a region must be filled). // // An alternative to the simple loop below: clear during post_compact(), // which uses memcpy instead of individual stores, and is easy to // parallelize. (The downside is that it clears the entire RegionData // object as opposed to just one field.) // // post_compact() would have to clear the summary data up to the highest // address that was written during the summary phase, which would be // // max(top, max(new_top, clear_top)) // // where clear_top is a new field in SpaceInfo. Would have to set clear_top // to target_end. const RegionData* const sr = region(split_region); const size_t beg_idx = addr_to_region_idx(region_align_up(sr->destination() + sr->partial_obj_size())); const size_t end_idx = addr_to_region_idx(target_end); if (TraceParallelOldGCSummaryPhase) { gclog_or_tty->print_cr("split: clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx); } for (size_t idx = beg_idx; idx < end_idx; ++idx) { _region_data[idx].set_source_region(0); } // Set split_destination and partial_obj_size to reflect the split region. split_destination = sr->destination(); partial_obj_size = sr->partial_obj_size(); } // The split is recorded only if a partial object extends onto the region. if (partial_obj_size != 0) { _region_data[split_region].set_partial_obj_size(0); split_info.record(split_region, partial_obj_size, split_destination); } // Setup the continuation addresses. *target_next = split_destination + partial_obj_size; HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size; if (TraceParallelOldGCSummaryPhase) { const char * split_type = partial_obj_size == 0 ? "easy" : "hard"; gclog_or_tty->print_cr("%s split: src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT, split_type, source_next, split_region, partial_obj_size); gclog_or_tty->print_cr("%s split: dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT, split_type, split_destination, addr_to_region_idx(split_destination), *target_next); if (partial_obj_size != 0) { HeapWord* const po_beg = split_info.destination(); HeapWord* const po_end = po_beg + split_info.partial_obj_size(); gclog_or_tty->print_cr("%s split: " "po_beg=" PTR_FORMAT " " SIZE_FORMAT " " "po_end=" PTR_FORMAT " " SIZE_FORMAT, split_type, po_beg, addr_to_region_idx(po_beg), po_end, addr_to_region_idx(po_end)); } } return source_next; } bool ParallelCompactData::summarize(SplitInfo& split_info, HeapWord* source_beg, HeapWord* source_end, HeapWord** source_next, HeapWord* target_beg, HeapWord* target_end, HeapWord** target_next) { if (TraceParallelOldGCSummaryPhase) { HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next; tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT, source_beg, source_end, source_next_val, target_beg, target_end, *target_next); } size_t cur_region = addr_to_region_idx(source_beg); const size_t end_region = addr_to_region_idx(region_align_up(source_end)); HeapWord *dest_addr = target_beg; while (cur_region < end_region) { // The destination must be set even if the region has no data. _region_data[cur_region].set_destination(dest_addr); size_t words = _region_data[cur_region].data_size(); if (words > 0) { // If cur_region does not fit entirely into the target space, find a point // at which the source space can be 'split' so that part is copied to the // target space and the rest is copied elsewhere. if (dest_addr + words > target_end) { assert(source_next != NULL, "source_next is NULL when splitting"); *source_next = summarize_split_space(cur_region, split_info, dest_addr, target_end, target_next); return false; } // Compute the destination_count for cur_region, and if necessary, update // source_region for a destination region. The source_region field is // updated if cur_region is the first (left-most) region to be copied to a // destination region. // // The destination_count calculation is a bit subtle. A region that has // data that compacts into itself does not count itself as a destination. // This maintains the invariant that a zero count means the region is // available and can be claimed and then filled. uint destination_count = 0; if (split_info.is_split(cur_region)) { // The current region has been split: the partial object will be copied // to one destination space and the remaining data will be copied to // another destination space. Adjust the initial destination_count and, // if necessary, set the source_region field if the partial object will // cross a destination region boundary. destination_count = split_info.destination_count(); if (destination_count == 2) { size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr()); _region_data[dest_idx].set_source_region(cur_region); } } HeapWord* const last_addr = dest_addr + words - 1; const size_t dest_region_1 = addr_to_region_idx(dest_addr); const size_t dest_region_2 = addr_to_region_idx(last_addr); // Initially assume that the destination regions will be the same and // adjust the value below if necessary. Under this assumption, if // cur_region == dest_region_2, then cur_region will be compacted // completely into itself. destination_count += cur_region == dest_region_2 ? 0 : 1; if (dest_region_1 != dest_region_2) { // Destination regions differ; adjust destination_count. destination_count += 1; // Data from cur_region will be copied to the start of dest_region_2. _region_data[dest_region_2].set_source_region(cur_region); } else if (region_offset(dest_addr) == 0) { // Data from cur_region will be copied to the start of the destination // region. _region_data[dest_region_1].set_source_region(cur_region); } _region_data[cur_region].set_destination_count(destination_count); _region_data[cur_region].set_data_location(region_to_addr(cur_region)); dest_addr += words; } ++cur_region; } *target_next = dest_addr; return true; } HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr) { assert(addr != NULL, "Should detect NULL oop earlier"); assert(PSParallelCompact::gc_heap()->is_in(addr), "not in heap"); assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked"); // Region covering the object. RegionData* const region_ptr = addr_to_region_ptr(addr); HeapWord* result = region_ptr->destination(); // If the entire Region is live, the new location is region->destination + the // offset of the object within in the Region. // Run some performance tests to determine if this special case pays off. It // is worth it for pointers into the dense prefix. If the optimization to // avoid pointer updates in regions that only point to the dense prefix is // ever implemented, this should be revisited. if (region_ptr->data_size() == RegionSize) { result += region_offset(addr); return result; } // Otherwise, the new location is region->destination + block offset + the // number of live words in the Block that are (a) to the left of addr and (b) // due to objects that start in the Block. // Fill in the block table if necessary. This is unsynchronized, so multiple // threads may fill the block table for a region (harmless, since it is // idempotent). if (!region_ptr->blocks_filled()) { PSParallelCompact::fill_blocks(addr_to_region_idx(addr)); region_ptr->set_blocks_filled(); } HeapWord* const search_start = block_align_down(addr); const size_t block_offset = addr_to_block_ptr(addr)->offset(); const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap(); const size_t live = bitmap->live_words_in_range(search_start, oop(addr)); result += block_offset + live; DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result)); return result; } #ifdef ASSERT void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace) { const size_t* const beg = (const size_t*)vspace->committed_low_addr(); const size_t* const end = (const size_t*)vspace->committed_high_addr(); for (const size_t* p = beg; p < end; ++p) { assert(*p == 0, "not zero"); } } void ParallelCompactData::verify_clear() { verify_clear(_region_vspace); verify_clear(_block_vspace); } #endif // #ifdef ASSERT STWGCTimer PSParallelCompact::_gc_timer; ParallelOldTracer PSParallelCompact::_gc_tracer; elapsedTimer PSParallelCompact::_accumulated_time; unsigned int PSParallelCompact::_total_invocations = 0; unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0; jlong PSParallelCompact::_time_of_last_gc = 0; CollectorCounters* PSParallelCompact::_counters = NULL; ParMarkBitMap PSParallelCompact::_mark_bitmap; ParallelCompactData PSParallelCompact::_summary_data; PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure; bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); } void PSParallelCompact::KeepAliveClosure::do_oop(oop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); } void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); } PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure; PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure; void PSParallelCompact::AdjustPointerClosure::do_oop(oop* p) { adjust_pointer(p); } void PSParallelCompact::AdjustPointerClosure::do_oop(narrowOop* p) { adjust_pointer(p); } void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); } void PSParallelCompact::MarkAndPushClosure::do_oop(oop* p) { mark_and_push(_compaction_manager, p); } void PSParallelCompact::MarkAndPushClosure::do_oop(narrowOop* p) { mark_and_push(_compaction_manager, p); } void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) { klass->oops_do(_mark_and_push_closure); } void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) { klass->oops_do(&PSParallelCompact::_adjust_pointer_closure); } void PSParallelCompact::post_initialize() { ParallelScavengeHeap* heap = gc_heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); MemRegion mr = heap->reserved_region(); _ref_processor = new ReferenceProcessor(mr, // span ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing (int) ParallelGCThreads, // mt processing degree true, // mt discovery (int) ParallelGCThreads, // mt discovery degree true, // atomic_discovery &_is_alive_closure); // non-header is alive closure _counters = new CollectorCounters("PSParallelCompact", 1); // Initialize static fields in ParCompactionManager. ParCompactionManager::initialize(mark_bitmap()); } bool PSParallelCompact::initialize() { ParallelScavengeHeap* heap = gc_heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); MemRegion mr = heap->reserved_region(); // Was the old gen get allocated successfully? if (!heap->old_gen()->is_allocated()) { return false; } initialize_space_info(); initialize_dead_wood_limiter(); if (!_mark_bitmap.initialize(mr)) { vm_shutdown_during_initialization( err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel " "garbage collection for the requested " SIZE_FORMAT "KB heap.", _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K)); return false; } if (!_summary_data.initialize(mr)) { vm_shutdown_during_initialization( err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel " "garbage collection for the requested " SIZE_FORMAT "KB heap.", _summary_data.reserved_byte_size()/K, mr.byte_size()/K)); return false; } return true; } void PSParallelCompact::initialize_space_info() { memset(&_space_info, 0, sizeof(_space_info)); ParallelScavengeHeap* heap = gc_heap(); PSYoungGen* young_gen = heap->young_gen(); _space_info[old_space_id].set_space(heap->old_gen()->object_space()); _space_info[eden_space_id].set_space(young_gen->eden_space()); _space_info[from_space_id].set_space(young_gen->from_space()); _space_info[to_space_id].set_space(young_gen->to_space()); _space_info[old_space_id].set_start_array(heap->old_gen()->start_array()); } void PSParallelCompact::initialize_dead_wood_limiter() { const size_t max = 100; _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0; _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0; _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev); DEBUG_ONLY(_dwl_initialized = true;) _dwl_adjustment = normal_distribution(1.0); } // Simple class for storing info about the heap at the start of GC, to be used // after GC for comparison/printing. class PreGCValues { public: PreGCValues() { } PreGCValues(ParallelScavengeHeap* heap) { fill(heap); } void fill(ParallelScavengeHeap* heap) { _heap_used = heap->used(); _young_gen_used = heap->young_gen()->used_in_bytes(); _old_gen_used = heap->old_gen()->used_in_bytes(); _metadata_used = MetaspaceAux::used_bytes(); }; size_t heap_used() const { return _heap_used; } size_t young_gen_used() const { return _young_gen_used; } size_t old_gen_used() const { return _old_gen_used; } size_t metadata_used() const { return _metadata_used; } private: size_t _heap_used; size_t _young_gen_used; size_t _old_gen_used; size_t _metadata_used; }; void PSParallelCompact::clear_data_covering_space(SpaceId id) { // At this point, top is the value before GC, new_top() is the value that will // be set at the end of GC. The marking bitmap is cleared to top; nothing // should be marked above top. The summary data is cleared to the larger of // top & new_top. MutableSpace* const space = _space_info[id].space(); HeapWord* const bot = space->bottom(); HeapWord* const top = space->top(); HeapWord* const max_top = MAX2(top, _space_info[id].new_top()); const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot); const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top)); _mark_bitmap.clear_range(beg_bit, end_bit); const size_t beg_region = _summary_data.addr_to_region_idx(bot); const size_t end_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top)); _summary_data.clear_range(beg_region, end_region); // Clear the data used to 'split' regions. SplitInfo& split_info = _space_info[id].split_info(); if (split_info.is_valid()) { split_info.clear(); } DEBUG_ONLY(split_info.verify_clear();) } void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values) { // Update the from & to space pointers in space_info, since they are swapped // at each young gen gc. Do the update unconditionally (even though a // promotion failure does not swap spaces) because an unknown number of minor // collections will have swapped the spaces an unknown number of times. GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ParallelScavengeHeap* heap = gc_heap(); _space_info[from_space_id].set_space(heap->young_gen()->from_space()); _space_info[to_space_id].set_space(heap->young_gen()->to_space()); pre_gc_values->fill(heap); DEBUG_ONLY(add_obj_count = add_obj_size = 0;) DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;) // Increment the invocation count heap->increment_total_collections(true); // We need to track unique mark sweep invocations as well. _total_invocations++; heap->print_heap_before_gc(); heap->trace_heap_before_gc(&_gc_tracer); // Fill in TLABs heap->accumulate_statistics_all_tlabs(); heap->ensure_parsability(true); // retire TLABs if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { HandleMark hm; // Discard invalid handles created during verification Universe::verify(" VerifyBeforeGC:"); } // Verify object start arrays if (VerifyObjectStartArray && VerifyBeforeGC) { heap->old_gen()->verify_object_start_array(); } DEBUG_ONLY(mark_bitmap()->verify_clear();) DEBUG_ONLY(summary_data().verify_clear();) // Have worker threads release resources the next time they run a task. gc_task_manager()->release_all_resources(); } void PSParallelCompact::post_compact() { GCTraceTime tm("post compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); for (unsigned int id = old_space_id; id < last_space_id; ++id) { // Clear the marking bitmap, summary data and split info. clear_data_covering_space(SpaceId(id)); // Update top(). Must be done after clearing the bitmap and summary data. _space_info[id].publish_new_top(); } MutableSpace* const eden_space = _space_info[eden_space_id].space(); MutableSpace* const from_space = _space_info[from_space_id].space(); MutableSpace* const to_space = _space_info[to_space_id].space(); ParallelScavengeHeap* heap = gc_heap(); bool eden_empty = eden_space->is_empty(); if (!eden_empty) { eden_empty = absorb_live_data_from_eden(heap->size_policy(), heap->young_gen(), heap->old_gen()); } // Update heap occupancy information which is used as input to the soft ref // clearing policy at the next gc. Universe::update_heap_info_at_gc(); bool young_gen_empty = eden_empty && from_space->is_empty() && to_space->is_empty(); BarrierSet* bs = heap->barrier_set(); if (bs->is_a(BarrierSet::ModRef)) { ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs; MemRegion old_mr = heap->old_gen()->reserved(); if (young_gen_empty) { modBS->clear(MemRegion(old_mr.start(), old_mr.end())); } else { modBS->invalidate(MemRegion(old_mr.start(), old_mr.end())); } } // Delete metaspaces for unloaded class loaders and clean up loader_data graph ClassLoaderDataGraph::purge(); MetaspaceAux::verify_metrics(); Threads::gc_epilogue(); CodeCache::gc_epilogue(); JvmtiExport::gc_epilogue(); COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); ref_processor()->enqueue_discovered_references(NULL); if (ZapUnusedHeapArea) { heap->gen_mangle_unused_area(); } // Update time of last GC reset_millis_since_last_gc(); } HeapWord* PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id, bool maximum_compaction) { const size_t region_size = ParallelCompactData::RegionSize; const ParallelCompactData& sd = summary_data(); const MutableSpace* const space = _space_info[id].space(); HeapWord* const top_aligned_up = sd.region_align_up(space->top()); const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom()); const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up); // Skip full regions at the beginning of the space--they are necessarily part // of the dense prefix. size_t full_count = 0; const RegionData* cp; for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) { ++full_count; } assert(total_invocations() >= _maximum_compaction_gc_num, "sanity"); const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num; const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval; if (maximum_compaction || cp == end_cp || interval_ended) { _maximum_compaction_gc_num = total_invocations(); return sd.region_to_addr(cp); } HeapWord* const new_top = _space_info[id].new_top(); const size_t space_live = pointer_delta(new_top, space->bottom()); const size_t space_used = space->used_in_words(); const size_t space_capacity = space->capacity_in_words(); const double cur_density = double(space_live) / space_capacity; const double deadwood_density = (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density; const size_t deadwood_goal = size_t(space_capacity * deadwood_density); if (TraceParallelOldGCDensePrefix) { tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT, cur_density, deadwood_density, deadwood_goal); tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " " "space_cap=" SIZE_FORMAT, space_live, space_used, space_capacity); } // XXX - Use binary search? HeapWord* dense_prefix = sd.region_to_addr(cp); const RegionData* full_cp = cp; const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1); while (cp < end_cp) { HeapWord* region_destination = cp->destination(); const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination); if (TraceParallelOldGCDensePrefix && Verbose) { tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " " "dp=" SIZE_FORMAT_W(8) " " "cdw=" SIZE_FORMAT_W(8), sd.region(cp), region_destination, dense_prefix, cur_deadwood); } if (cur_deadwood >= deadwood_goal) { // Found the region that has the correct amount of deadwood to the left. // This typically occurs after crossing a fairly sparse set of regions, so // iterate backwards over those sparse regions, looking for the region // that has the lowest density of live objects 'to the right.' size_t space_to_left = sd.region(cp) * region_size; size_t live_to_left = space_to_left - cur_deadwood; size_t space_to_right = space_capacity - space_to_left; size_t live_to_right = space_live - live_to_left; double density_to_right = double(live_to_right) / space_to_right; while (cp > full_cp) { --cp; const size_t prev_region_live_to_right = live_to_right - cp->data_size(); const size_t prev_region_space_to_right = space_to_right + region_size; double prev_region_density_to_right = double(prev_region_live_to_right) / prev_region_space_to_right; if (density_to_right <= prev_region_density_to_right) { return dense_prefix; } if (TraceParallelOldGCDensePrefix && Verbose) { tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f " "pc_d2r=%10.8f", sd.region(cp), density_to_right, prev_region_density_to_right); } dense_prefix -= region_size; live_to_right = prev_region_live_to_right; space_to_right = prev_region_space_to_right; density_to_right = prev_region_density_to_right; } return dense_prefix; } dense_prefix += region_size; ++cp; } return dense_prefix; } #ifndef PRODUCT void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm, const SpaceId id, const bool maximum_compaction, HeapWord* const addr) { const size_t region_idx = summary_data().addr_to_region_idx(addr); RegionData* const cp = summary_data().region(region_idx); const MutableSpace* const space = _space_info[id].space(); HeapWord* const new_top = _space_info[id].new_top(); const size_t space_live = pointer_delta(new_top, space->bottom()); const size_t dead_to_left = pointer_delta(addr, cp->destination()); const size_t space_cap = space->capacity_in_words(); const double dead_to_left_pct = double(dead_to_left) / space_cap; const size_t live_to_right = new_top - cp->destination(); const size_t dead_to_right = space->top() - addr - live_to_right; tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " " "spl=" SIZE_FORMAT " " "d2l=" SIZE_FORMAT " d2l%%=%6.4f " "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT " ratio=%10.8f", algorithm, addr, region_idx, space_live, dead_to_left, dead_to_left_pct, dead_to_right, live_to_right, double(dead_to_right) / live_to_right); } #endif // #ifndef PRODUCT // Return a fraction indicating how much of the generation can be treated as // "dead wood" (i.e., not reclaimed). The function uses a normal distribution // based on the density of live objects in the generation to determine a limit, // which is then adjusted so the return value is min_percent when the density is // 1. // // The following table shows some return values for a different values of the // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and // min_percent is 1. // // fraction allowed as dead wood // ----------------------------------------------------------------- // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95 // ------- ---------- ---------- ---------- ---------- ---------- ---------- // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent) { assert(_dwl_initialized, "uninitialized"); // The raw limit is the value of the normal distribution at x = density. const double raw_limit = normal_distribution(density); // Adjust the raw limit so it becomes the minimum when the density is 1. // // First subtract the adjustment value (which is simply the precomputed value // normal_distribution(1.0)); this yields a value of 0 when the density is 1. // Then add the minimum value, so the minimum is returned when the density is // 1. Finally, prevent negative values, which occur when the mean is not 0.5. const double min = double(min_percent) / 100.0; const double limit = raw_limit - _dwl_adjustment + min; return MAX2(limit, 0.0); } ParallelCompactData::RegionData* PSParallelCompact::first_dead_space_region(const RegionData* beg, const RegionData* end) { const size_t region_size = ParallelCompactData::RegionSize; ParallelCompactData& sd = summary_data(); size_t left = sd.region(beg); size_t right = end > beg ? sd.region(end) - 1 : left; // Binary search. while (left < right) { // Equivalent to (left + right) / 2, but does not overflow. const size_t middle = left + (right - left) / 2; RegionData* const middle_ptr = sd.region(middle); HeapWord* const dest = middle_ptr->destination(); HeapWord* const addr = sd.region_to_addr(middle); assert(dest != NULL, "sanity"); assert(dest <= addr, "must move left"); if (middle > left && dest < addr) { right = middle - 1; } else if (middle < right && middle_ptr->data_size() == region_size) { left = middle + 1; } else { return middle_ptr; } } return sd.region(left); } ParallelCompactData::RegionData* PSParallelCompact::dead_wood_limit_region(const RegionData* beg, const RegionData* end, size_t dead_words) { ParallelCompactData& sd = summary_data(); size_t left = sd.region(beg); size_t right = end > beg ? sd.region(end) - 1 : left; // Binary search. while (left < right) { // Equivalent to (left + right) / 2, but does not overflow. const size_t middle = left + (right - left) / 2; RegionData* const middle_ptr = sd.region(middle); HeapWord* const dest = middle_ptr->destination(); HeapWord* const addr = sd.region_to_addr(middle); assert(dest != NULL, "sanity"); assert(dest <= addr, "must move left"); const size_t dead_to_left = pointer_delta(addr, dest); if (middle > left && dead_to_left > dead_words) { right = middle - 1; } else if (middle < right && dead_to_left < dead_words) { left = middle + 1; } else { return middle_ptr; } } return sd.region(left); } // The result is valid during the summary phase, after the initial summarization // of each space into itself, and before final summarization. inline double PSParallelCompact::reclaimed_ratio(const RegionData* const cp, HeapWord* const bottom, HeapWord* const top, HeapWord* const new_top) { ParallelCompactData& sd = summary_data(); assert(cp != NULL, "sanity"); assert(bottom != NULL, "sanity"); assert(top != NULL, "sanity"); assert(new_top != NULL, "sanity"); assert(top >= new_top, "summary data problem?"); assert(new_top > bottom, "space is empty; should not be here"); assert(new_top >= cp->destination(), "sanity"); assert(top >= sd.region_to_addr(cp), "sanity"); HeapWord* const destination = cp->destination(); const size_t dense_prefix_live = pointer_delta(destination, bottom); const size_t compacted_region_live = pointer_delta(new_top, destination); const size_t compacted_region_used = pointer_delta(top, sd.region_to_addr(cp)); const size_t reclaimable = compacted_region_used - compacted_region_live; const double divisor = dense_prefix_live + 1.25 * compacted_region_live; return double(reclaimable) / divisor; } // Return the address of the end of the dense prefix, a.k.a. the start of the // compacted region. The address is always on a region boundary. // // Completely full regions at the left are skipped, since no compaction can // occur in those regions. Then the maximum amount of dead wood to allow is // computed, based on the density (amount live / capacity) of the generation; // the region with approximately that amount of dead space to the left is // identified as the limit region. Regions between the last completely full // region and the limit region are scanned and the one that has the best // (maximum) reclaimed_ratio() is selected. HeapWord* PSParallelCompact::compute_dense_prefix(const SpaceId id, bool maximum_compaction) { if (ParallelOldGCSplitALot) { if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) { // The value was chosen to provoke splitting a young gen space; use it. return _space_info[id].dense_prefix(); } } const size_t region_size = ParallelCompactData::RegionSize; const ParallelCompactData& sd = summary_data(); const MutableSpace* const space = _space_info[id].space(); HeapWord* const top = space->top(); HeapWord* const top_aligned_up = sd.region_align_up(top); HeapWord* const new_top = _space_info[id].new_top(); HeapWord* const new_top_aligned_up = sd.region_align_up(new_top); HeapWord* const bottom = space->bottom(); const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom); const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up); const RegionData* const new_top_cp = sd.addr_to_region_ptr(new_top_aligned_up); // Skip full regions at the beginning of the space--they are necessarily part // of the dense prefix. const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp); assert(full_cp->destination() == sd.region_to_addr(full_cp) || space->is_empty(), "no dead space allowed to the left"); assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1, "region must have dead space"); // The gc number is saved whenever a maximum compaction is done, and used to // determine when the maximum compaction interval has expired. This avoids // successive max compactions for different reasons. assert(total_invocations() >= _maximum_compaction_gc_num, "sanity"); const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num; const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval || total_invocations() == HeapFirstMaximumCompactionCount; if (maximum_compaction || full_cp == top_cp || interval_ended) { _maximum_compaction_gc_num = total_invocations(); return sd.region_to_addr(full_cp); } const size_t space_live = pointer_delta(new_top, bottom); const size_t space_used = space->used_in_words(); const size_t space_capacity = space->capacity_in_words(); const double density = double(space_live) / double(space_capacity); const size_t min_percent_free = MarkSweepDeadRatio; const double limiter = dead_wood_limiter(density, min_percent_free); const size_t dead_wood_max = space_used - space_live; const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter), dead_wood_max); if (TraceParallelOldGCDensePrefix) { tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " " "space_cap=" SIZE_FORMAT, space_live, space_used, space_capacity); tty->print_cr("dead_wood_limiter(%6.4f, %d)=%6.4f " "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT, density, min_percent_free, limiter, dead_wood_max, dead_wood_limit); } // Locate the region with the desired amount of dead space to the left. const RegionData* const limit_cp = dead_wood_limit_region(full_cp, top_cp, dead_wood_limit); // Scan from the first region with dead space to the limit region and find the // one with the best (largest) reclaimed ratio. double best_ratio = 0.0; const RegionData* best_cp = full_cp; for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) { double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top); if (tmp_ratio > best_ratio) { best_cp = cp; best_ratio = tmp_ratio; } } #if 0 // Something to consider: if the region with the best ratio is 'close to' the // first region w/free space, choose the first region with free space // ("first-free"). The first-free region is usually near the start of the // heap, which means we are copying most of the heap already, so copy a bit // more to get complete compaction. if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) { _maximum_compaction_gc_num = total_invocations(); best_cp = full_cp; } #endif // #if 0 return sd.region_to_addr(best_cp); } #ifndef PRODUCT void PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start, size_t words) { if (TraceParallelOldGCSummaryPhase) { tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") " SIZE_FORMAT, start, start + words, words); } ObjectStartArray* const start_array = _space_info[id].start_array(); CollectedHeap::fill_with_objects(start, words); for (HeapWord* p = start; p < start + words; p += oop(p)->size()) { _mark_bitmap.mark_obj(p, words); _summary_data.add_obj(p, words); start_array->allocate_block(p); } } void PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start) { ParallelCompactData& sd = summary_data(); MutableSpace* space = _space_info[id].space(); // Find the source and destination start addresses. HeapWord* const src_addr = sd.region_align_down(start); HeapWord* dst_addr; if (src_addr < start) { dst_addr = sd.addr_to_region_ptr(src_addr)->destination(); } else if (src_addr > space->bottom()) { // The start (the original top() value) is aligned to a region boundary so // the associated region does not have a destination. Compute the // destination from the previous region. RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1; dst_addr = cp->destination() + cp->data_size(); } else { // Filling the entire space. dst_addr = space->bottom(); } assert(dst_addr != NULL, "sanity"); // Update the summary data. bool result = _summary_data.summarize(_space_info[id].split_info(), src_addr, space->top(), NULL, dst_addr, space->end(), _space_info[id].new_top_addr()); assert(result, "should not fail: bad filler object size"); } void PSParallelCompact::provoke_split_fill_survivor(SpaceId id) { if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) { return; } MutableSpace* const space = _space_info[id].space(); if (space->is_empty()) { HeapWord* b = space->bottom(); HeapWord* t = b + space->capacity_in_words() / 2; space->set_top(t); if (ZapUnusedHeapArea) { space->set_top_for_allocations(); } size_t min_size = CollectedHeap::min_fill_size(); size_t obj_len = min_size; while (b + obj_len <= t) { CollectedHeap::fill_with_object(b, obj_len); mark_bitmap()->mark_obj(b, obj_len); summary_data().add_obj(b, obj_len); b += obj_len; obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ... } if (b < t) { // The loop didn't completely fill to t (top); adjust top downward. space->set_top(b); if (ZapUnusedHeapArea) { space->set_top_for_allocations(); } } HeapWord** nta = _space_info[id].new_top_addr(); bool result = summary_data().summarize(_space_info[id].split_info(), space->bottom(), space->top(), NULL, space->bottom(), space->end(), nta); assert(result, "space must fit into itself"); } } void PSParallelCompact::provoke_split(bool & max_compaction) { if (total_invocations() % ParallelOldGCSplitInterval != 0) { return; } const size_t region_size = ParallelCompactData::RegionSize; ParallelCompactData& sd = summary_data(); MutableSpace* const eden_space = _space_info[eden_space_id].space(); MutableSpace* const from_space = _space_info[from_space_id].space(); const size_t eden_live = pointer_delta(eden_space->top(), _space_info[eden_space_id].new_top()); const size_t from_live = pointer_delta(from_space->top(), _space_info[from_space_id].new_top()); const size_t min_fill_size = CollectedHeap::min_fill_size(); const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top()); const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0; const size_t from_free = pointer_delta(from_space->end(), from_space->top()); const size_t from_fillable = from_free >= min_fill_size ? from_free : 0; // Choose the space to split; need at least 2 regions live (or fillable). SpaceId id; MutableSpace* space; size_t live_words; size_t fill_words; if (eden_live + eden_fillable >= region_size * 2) { id = eden_space_id; space = eden_space; live_words = eden_live; fill_words = eden_fillable; } else if (from_live + from_fillable >= region_size * 2) { id = from_space_id; space = from_space; live_words = from_live; fill_words = from_fillable; } else { return; // Give up. } assert(fill_words == 0 || fill_words >= min_fill_size, "sanity"); if (live_words < region_size * 2) { // Fill from top() to end() w/live objects of mixed sizes. HeapWord* const fill_start = space->top(); live_words += fill_words; space->set_top(fill_start + fill_words); if (ZapUnusedHeapArea) { space->set_top_for_allocations(); } HeapWord* cur_addr = fill_start; while (fill_words > 0) { const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size; size_t cur_size = MIN2(align_object_size_(r), fill_words); if (fill_words - cur_size < min_fill_size) { cur_size = fill_words; // Avoid leaving a fragment too small to fill. } CollectedHeap::fill_with_object(cur_addr, cur_size); mark_bitmap()->mark_obj(cur_addr, cur_size); sd.add_obj(cur_addr, cur_size); cur_addr += cur_size; fill_words -= cur_size; } summarize_new_objects(id, fill_start); } max_compaction = false; // Manipulate the old gen so that it has room for about half of the live data // in the target young gen space (live_words / 2). id = old_space_id; space = _space_info[id].space(); const size_t free_at_end = space->free_in_words(); const size_t free_target = align_object_size(live_words / 2); const size_t dead = pointer_delta(space->top(), _space_info[id].new_top()); if (free_at_end >= free_target + min_fill_size) { // Fill space above top() and set the dense prefix so everything survives. HeapWord* const fill_start = space->top(); const size_t fill_size = free_at_end - free_target; space->set_top(space->top() + fill_size); if (ZapUnusedHeapArea) { space->set_top_for_allocations(); } fill_with_live_objects(id, fill_start, fill_size); summarize_new_objects(id, fill_start); _space_info[id].set_dense_prefix(sd.region_align_down(space->top())); } else if (dead + free_at_end > free_target) { // Find a dense prefix that makes the right amount of space available. HeapWord* cur = sd.region_align_down(space->top()); HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination(); size_t dead_to_right = pointer_delta(space->end(), cur_destination); while (dead_to_right < free_target) { cur -= region_size; cur_destination = sd.addr_to_region_ptr(cur)->destination(); dead_to_right = pointer_delta(space->end(), cur_destination); } _space_info[id].set_dense_prefix(cur); } } #endif // #ifndef PRODUCT void PSParallelCompact::summarize_spaces_quick() { for (unsigned int i = 0; i < last_space_id; ++i) { const MutableSpace* space = _space_info[i].space(); HeapWord** nta = _space_info[i].new_top_addr(); bool result = _summary_data.summarize(_space_info[i].split_info(), space->bottom(), space->top(), NULL, space->bottom(), space->end(), nta); assert(result, "space must fit into itself"); _space_info[i].set_dense_prefix(space->bottom()); } #ifndef PRODUCT if (ParallelOldGCSplitALot) { provoke_split_fill_survivor(to_space_id); } #endif // #ifndef PRODUCT } void PSParallelCompact::fill_dense_prefix_end(SpaceId id) { HeapWord* const dense_prefix_end = dense_prefix(id); const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end); const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end); if (dead_space_crosses_boundary(region, dense_prefix_bit)) { // Only enough dead space is filled so that any remaining dead space to the // left is larger than the minimum filler object. (The remainder is filled // during the copy/update phase.) // // The size of the dead space to the right of the boundary is not a // concern, since compaction will be able to use whatever space is // available. // // Here '||' is the boundary, 'x' represents a don't care bit and a box // surrounds the space to be filled with an object. // // In the 32-bit VM, each bit represents two 32-bit words: // +---+ // a) beg_bits: ... x x x | 0 | || 0 x x ... // end_bits: ... x x x | 0 | || 0 x x ... // +---+ // // In the 64-bit VM, each bit represents one 64-bit word: // +------------+ // b) beg_bits: ... x x x | 0 || 0 | x x ... // end_bits: ... x x 1 | 0 || 0 | x x ... // +------------+ // +-------+ // c) beg_bits: ... x x | 0 0 | || 0 x x ... // end_bits: ... x 1 | 0 0 | || 0 x x ... // +-------+ // +-----------+ // d) beg_bits: ... x | 0 0 0 | || 0 x x ... // end_bits: ... 1 | 0 0 0 | || 0 x x ... // +-----------+ // +-------+ // e) beg_bits: ... 0 0 | 0 0 | || 0 x x ... // end_bits: ... 0 0 | 0 0 | || 0 x x ... // +-------+ // Initially assume case a, c or e will apply. size_t obj_len = CollectedHeap::min_fill_size(); HeapWord* obj_beg = dense_prefix_end - obj_len; #ifdef _LP64 if (MinObjAlignment > 1) { // object alignment > heap word size // Cases a, c or e. } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) { // Case b above. obj_beg = dense_prefix_end - 1; } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) && _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) { // Case d above. obj_beg = dense_prefix_end - 3; obj_len = 3; } #endif // #ifdef _LP64 CollectedHeap::fill_with_object(obj_beg, obj_len); _mark_bitmap.mark_obj(obj_beg, obj_len); _summary_data.add_obj(obj_beg, obj_len); assert(start_array(id) != NULL, "sanity"); start_array(id)->allocate_block(obj_beg); } } void PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr) { RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr); HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr); RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up); for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) { cur->set_source_region(0); } } void PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction) { assert(id < last_space_id, "id out of range"); assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() || ParallelOldGCSplitALot && id == old_space_id, "should have been reset in summarize_spaces_quick()"); const MutableSpace* space = _space_info[id].space(); if (_space_info[id].new_top() != space->bottom()) { HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction); _space_info[id].set_dense_prefix(dense_prefix_end); #ifndef PRODUCT if (TraceParallelOldGCDensePrefix) { print_dense_prefix_stats("ratio", id, maximum_compaction, dense_prefix_end); HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction); print_dense_prefix_stats("density", id, maximum_compaction, addr); } #endif // #ifndef PRODUCT // Recompute the summary data, taking into account the dense prefix. If // every last byte will be reclaimed, then the existing summary data which // compacts everything can be left in place. if (!maximum_compaction && dense_prefix_end != space->bottom()) { // If dead space crosses the dense prefix boundary, it is (at least // partially) filled with a dummy object, marked live and added to the // summary data. This simplifies the copy/update phase and must be done // before the final locations of objects are determined, to prevent // leaving a fragment of dead space that is too small to fill. fill_dense_prefix_end(id); // Compute the destination of each Region, and thus each object. _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end); _summary_data.summarize(_space_info[id].split_info(), dense_prefix_end, space->top(), NULL, dense_prefix_end, space->end(), _space_info[id].new_top_addr()); } } if (TraceParallelOldGCSummaryPhase) { const size_t region_size = ParallelCompactData::RegionSize; HeapWord* const dense_prefix_end = _space_info[id].dense_prefix(); const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end); const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom()); HeapWord* const new_top = _space_info[id].new_top(); const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top); const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end); tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " " "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " " "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT, id, space->capacity_in_words(), dense_prefix_end, dp_region, dp_words / region_size, cr_words / region_size, new_top); } } #ifndef PRODUCT void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id, HeapWord* dst_beg, HeapWord* dst_end, SpaceId src_space_id, HeapWord* src_beg, HeapWord* src_end) { if (TraceParallelOldGCSummaryPhase) { tty->print_cr("summarizing %d [%s] into %d [%s]: " "src=" PTR_FORMAT "-" PTR_FORMAT " " SIZE_FORMAT "-" SIZE_FORMAT " " "dst=" PTR_FORMAT "-" PTR_FORMAT " " SIZE_FORMAT "-" SIZE_FORMAT, src_space_id, space_names[src_space_id], dst_space_id, space_names[dst_space_id], src_beg, src_end, _summary_data.addr_to_region_idx(src_beg), _summary_data.addr_to_region_idx(src_end), dst_beg, dst_end, _summary_data.addr_to_region_idx(dst_beg), _summary_data.addr_to_region_idx(dst_end)); } } #endif // #ifndef PRODUCT void PSParallelCompact::summary_phase(ParCompactionManager* cm, bool maximum_compaction) { GCTraceTime tm("summary phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); // trace("2"); #ifdef ASSERT if (TraceParallelOldGCMarkingPhase) { tty->print_cr("add_obj_count=" SIZE_FORMAT " " "add_obj_bytes=" SIZE_FORMAT, add_obj_count, add_obj_size * HeapWordSize); tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " " "mark_bitmap_bytes=" SIZE_FORMAT, mark_bitmap_count, mark_bitmap_size * HeapWordSize); } #endif // #ifdef ASSERT // Quick summarization of each space into itself, to see how much is live. summarize_spaces_quick(); if (TraceParallelOldGCSummaryPhase) { tty->print_cr("summary_phase: after summarizing each space to self"); Universe::print(); NOT_PRODUCT(print_region_ranges()); if (Verbose) { NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info)); } } // The amount of live data that will end up in old space (assuming it fits). size_t old_space_total_live = 0; for (unsigned int id = old_space_id; id < last_space_id; ++id) { old_space_total_live += pointer_delta(_space_info[id].new_top(), _space_info[id].space()->bottom()); } MutableSpace* const old_space = _space_info[old_space_id].space(); const size_t old_capacity = old_space->capacity_in_words(); if (old_space_total_live > old_capacity) { // XXX - should also try to expand maximum_compaction = true; } #ifndef PRODUCT if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) { provoke_split(maximum_compaction); } #endif // #ifndef PRODUCT // Old generations. summarize_space(old_space_id, maximum_compaction); // Summarize the remaining spaces in the young gen. The initial target space // is the old gen. If a space does not fit entirely into the target, then the // remainder is compacted into the space itself and that space becomes the new // target. SpaceId dst_space_id = old_space_id; HeapWord* dst_space_end = old_space->end(); HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr(); for (unsigned int id = eden_space_id; id < last_space_id; ++id) { const MutableSpace* space = _space_info[id].space(); const size_t live = pointer_delta(_space_info[id].new_top(), space->bottom()); const size_t available = pointer_delta(dst_space_end, *new_top_addr); NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end, SpaceId(id), space->bottom(), space->top());) if (live > 0 && live <= available) { // All the live data will fit. bool done = _summary_data.summarize(_space_info[id].split_info(), space->bottom(), space->top(), NULL, *new_top_addr, dst_space_end, new_top_addr); assert(done, "space must fit into old gen"); // Reset the new_top value for the space. _space_info[id].set_new_top(space->bottom()); } else if (live > 0) { // Attempt to fit part of the source space into the target space. HeapWord* next_src_addr = NULL; bool done = _summary_data.summarize(_space_info[id].split_info(), space->bottom(), space->top(), &next_src_addr, *new_top_addr, dst_space_end, new_top_addr); assert(!done, "space should not fit into old gen"); assert(next_src_addr != NULL, "sanity"); // The source space becomes the new target, so the remainder is compacted // within the space itself. dst_space_id = SpaceId(id); dst_space_end = space->end(); new_top_addr = _space_info[id].new_top_addr(); NOT_PRODUCT(summary_phase_msg(dst_space_id, space->bottom(), dst_space_end, SpaceId(id), next_src_addr, space->top());) done = _summary_data.summarize(_space_info[id].split_info(), next_src_addr, space->top(), NULL, space->bottom(), dst_space_end, new_top_addr); assert(done, "space must fit when compacted into itself"); assert(*new_top_addr <= space->top(), "usage should not grow"); } } if (TraceParallelOldGCSummaryPhase) { tty->print_cr("summary_phase: after final summarization"); Universe::print(); NOT_PRODUCT(print_region_ranges()); if (Verbose) { NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info)); } } } // This method should contain all heap-specific policy for invoking a full // collection. invoke_no_policy() will only attempt to compact the heap; it // will do nothing further. If we need to bail out for policy reasons, scavenge // before full gc, or any other specialized behavior, it needs to be added here. // // Note that this method should only be called from the vm_thread while at a // safepoint. // // Note that the all_soft_refs_clear flag in the collector policy // may be true because this method can be called without intervening // activity. For example when the heap space is tight and full measure // are being taken to free space. void PSParallelCompact::invoke(bool maximum_heap_compaction) { assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); ParallelScavengeHeap* heap = gc_heap(); GCCause::Cause gc_cause = heap->gc_cause(); assert(!heap->is_gc_active(), "not reentrant"); PSAdaptiveSizePolicy* policy = heap->size_policy(); IsGCActiveMark mark; if (ScavengeBeforeFullGC) { PSScavenge::invoke_no_policy(); } const bool clear_all_soft_refs = heap->collector_policy()->should_clear_all_soft_refs(); PSParallelCompact::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction); } // This method contains no policy. You should probably // be calling invoke() instead. bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) { assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); assert(ref_processor() != NULL, "Sanity"); if (GC_locker::check_active_before_gc()) { return false; } ParallelScavengeHeap* heap = gc_heap(); _gc_timer.register_gc_start(); _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start()); TimeStamp marking_start; TimeStamp compaction_start; TimeStamp collection_exit; GCCause::Cause gc_cause = heap->gc_cause(); PSYoungGen* young_gen = heap->young_gen(); PSOldGen* old_gen = heap->old_gen(); PSAdaptiveSizePolicy* size_policy = heap->size_policy(); // The scope of casr should end after code that can change // CollectorPolicy::_should_clear_all_soft_refs. ClearedAllSoftRefs casr(maximum_heap_compaction, heap->collector_policy()); if (ZapUnusedHeapArea) { // Save information needed to minimize mangling heap->record_gen_tops_before_GC(); } heap->pre_full_gc_dump(&_gc_timer); _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes; // Make sure data structures are sane, make the heap parsable, and do other // miscellaneous bookkeeping. PreGCValues pre_gc_values; pre_compact(&pre_gc_values); // Get the compaction manager reserved for the VM thread. ParCompactionManager* const vmthread_cm = ParCompactionManager::manager_array(gc_task_manager()->workers()); // Place after pre_compact() where the number of invocations is incremented. AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); { ResourceMark rm; HandleMark hm; // Set the number of GC threads to be used in this collection gc_task_manager()->set_active_gang(); gc_task_manager()->task_idle_workers(); heap->set_par_threads(gc_task_manager()->active_workers()); TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id()); TraceCollectorStats tcs(counters()); TraceMemoryManagerStats tms(true /* Full GC */,gc_cause); if (TraceGen1Time) accumulated_time()->start(); // Let the size policy know we're starting size_policy->major_collection_begin(); CodeCache::gc_prologue(); Threads::gc_prologue(); COMPILER2_PRESENT(DerivedPointerTable::clear()); ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); ref_processor()->setup_policy(maximum_heap_compaction); bool marked_for_unloading = false; marking_start.update(); marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer); bool max_on_system_gc = UseMaximumCompactionOnSystemGC && gc_cause == GCCause::_java_lang_system_gc; summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc); COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); // adjust_roots() updates Universe::_intArrayKlassObj which is // needed by the compaction for filling holes in the dense prefix. adjust_roots(); compaction_start.update(); compact(); // Reset the mark bitmap, summary data, and do other bookkeeping. Must be // done before resizing. post_compact(); // Let the size policy know we're done size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause); if (UseAdaptiveSizePolicy) { if (PrintAdaptiveSizePolicy) { gclog_or_tty->print("AdaptiveSizeStart: "); gclog_or_tty->stamp(); gclog_or_tty->print_cr(" collection: %d ", heap->total_collections()); if (Verbose) { gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d", old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes()); } } // Don't check if the size_policy is ready here. Let // the size_policy check that internally. if (UseAdaptiveGenerationSizePolicyAtMajorCollection && ((gc_cause != GCCause::_java_lang_system_gc) || UseAdaptiveSizePolicyWithSystemGC)) { // Calculate optimal free space amounts assert(young_gen->max_size() > young_gen->from_space()->capacity_in_bytes() + young_gen->to_space()->capacity_in_bytes(), "Sizes of space in young gen are out-of-bounds"); size_t young_live = young_gen->used_in_bytes(); size_t eden_live = young_gen->eden_space()->used_in_bytes(); size_t old_live = old_gen->used_in_bytes(); size_t cur_eden = young_gen->eden_space()->capacity_in_bytes(); size_t max_old_gen_size = old_gen->max_gen_size(); size_t max_eden_size = young_gen->max_size() - young_gen->from_space()->capacity_in_bytes() - young_gen->to_space()->capacity_in_bytes(); // Used for diagnostics size_policy->clear_generation_free_space_flags(); size_policy->compute_generations_free_space(young_live, eden_live, old_live, cur_eden, max_old_gen_size, max_eden_size, true /* full gc*/); size_policy->check_gc_overhead_limit(young_live, eden_live, max_old_gen_size, max_eden_size, true /* full gc*/, gc_cause, heap->collector_policy()); size_policy->decay_supplemental_growth(true /* full gc*/); heap->resize_old_gen( size_policy->calculated_old_free_size_in_bytes()); // Don't resize the young generation at an major collection. A // desired young generation size may have been calculated but // resizing the young generation complicates the code because the // resizing of the old generation may have moved the boundary // between the young generation and the old generation. Let the // young generation resizing happen at the minor collections. } if (PrintAdaptiveSizePolicy) { gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", heap->total_collections()); } } if (UsePerfData) { PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters(); counters->update_counters(); counters->update_old_capacity(old_gen->capacity_in_bytes()); counters->update_young_capacity(young_gen->capacity_in_bytes()); } heap->resize_all_tlabs(); // Resize the metaspace capactiy after a collection MetaspaceGC::compute_new_size(); if (TraceGen1Time) accumulated_time()->stop(); if (PrintGC) { if (PrintGCDetails) { // No GC timestamp here. This is after GC so it would be confusing. young_gen->print_used_change(pre_gc_values.young_gen_used()); old_gen->print_used_change(pre_gc_values.old_gen_used()); heap->print_heap_change(pre_gc_values.heap_used()); MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used()); } else { heap->print_heap_change(pre_gc_values.heap_used()); } } // Track memory usage and detect low memory MemoryService::track_memory_usage(); heap->update_counters(); gc_task_manager()->release_idle_workers(); } #ifdef ASSERT for (size_t i = 0; i < ParallelGCThreads + 1; ++i) { ParCompactionManager* const cm = ParCompactionManager::manager_array(int(i)); assert(cm->marking_stack()->is_empty(), "should be empty"); assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty"); } #endif // ASSERT if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { HandleMark hm; // Discard invalid handles created during verification Universe::verify(" VerifyAfterGC:"); } // Re-verify object start arrays if (VerifyObjectStartArray && VerifyAfterGC) { old_gen->verify_object_start_array(); } if (ZapUnusedHeapArea) { old_gen->object_space()->check_mangled_unused_area_complete(); } NOT_PRODUCT(ref_processor()->verify_no_references_recorded()); collection_exit.update(); heap->print_heap_after_gc(); heap->trace_heap_after_gc(&_gc_tracer); if (PrintGCTaskTimeStamps) { gclog_or_tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT, marking_start.ticks(), compaction_start.ticks(), collection_exit.ticks()); gc_task_manager()->print_task_time_stamps(); } heap->post_full_gc_dump(&_gc_timer); #ifdef TRACESPINNING ParallelTaskTerminator::print_termination_counts(); #endif _gc_timer.register_gc_end(); _gc_tracer.report_dense_prefix(dense_prefix(old_space_id)); _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions()); return true; } bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy, PSYoungGen* young_gen, PSOldGen* old_gen) { MutableSpace* const eden_space = young_gen->eden_space(); assert(!eden_space->is_empty(), "eden must be non-empty"); assert(young_gen->virtual_space()->alignment() == old_gen->virtual_space()->alignment(), "alignments do not match"); if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) { return false; } // Both generations must be completely committed. if (young_gen->virtual_space()->uncommitted_size() != 0) { return false; } if (old_gen->virtual_space()->uncommitted_size() != 0) { return false; } // Figure out how much to take from eden. Include the average amount promoted // in the total; otherwise the next young gen GC will simply bail out to a // full GC. const size_t alignment = old_gen->virtual_space()->alignment(); const size_t eden_used = eden_space->used_in_bytes(); const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average(); const size_t absorb_size = align_size_up(eden_used + promoted, alignment); const size_t eden_capacity = eden_space->capacity_in_bytes(); if (absorb_size >= eden_capacity) { return false; // Must leave some space in eden. } const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size; if (new_young_size < young_gen->min_gen_size()) { return false; // Respect young gen minimum size. } if (TraceAdaptiveGCBoundary && Verbose) { gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: " "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K " "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K " "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ", absorb_size / K, eden_capacity / K, (eden_capacity - absorb_size) / K, young_gen->from_space()->used_in_bytes() / K, young_gen->to_space()->used_in_bytes() / K, young_gen->capacity_in_bytes() / K, new_young_size / K); } // Fill the unused part of the old gen. MutableSpace* const old_space = old_gen->object_space(); HeapWord* const unused_start = old_space->top(); size_t const unused_words = pointer_delta(old_space->end(), unused_start); if (unused_words > 0) { if (unused_words < CollectedHeap::min_fill_size()) { return false; // If the old gen cannot be filled, must give up. } CollectedHeap::fill_with_objects(unused_start, unused_words); } // Take the live data from eden and set both top and end in the old gen to // eden top. (Need to set end because reset_after_change() mangles the region // from end to virtual_space->high() in debug builds). HeapWord* const new_top = eden_space->top(); old_gen->virtual_space()->expand_into(young_gen->virtual_space(), absorb_size); young_gen->reset_after_change(); old_space->set_top(new_top); old_space->set_end(new_top); old_gen->reset_after_change(); // Update the object start array for the filler object and the data from eden. ObjectStartArray* const start_array = old_gen->start_array(); for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) { start_array->allocate_block(p); } // Could update the promoted average here, but it is not typically updated at // full GCs and the value to use is unclear. Something like // // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc. size_policy->set_bytes_absorbed_from_eden(absorb_size); return true; } GCTaskManager* const PSParallelCompact::gc_task_manager() { assert(ParallelScavengeHeap::gc_task_manager() != NULL, "shouldn't return NULL"); return ParallelScavengeHeap::gc_task_manager(); } void PSParallelCompact::marking_phase(ParCompactionManager* cm, bool maximum_heap_compaction, ParallelOldTracer *gc_tracer) { // Recursively traverse all live objects and mark them GCTraceTime tm("marking phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ParallelScavengeHeap* heap = gc_heap(); uint parallel_gc_threads = heap->gc_task_manager()->workers(); uint active_gc_threads = heap->gc_task_manager()->active_workers(); TaskQueueSetSuper* qset = ParCompactionManager::stack_array(); ParallelTaskTerminator terminator(active_gc_threads, qset); PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm); PSParallelCompact::FollowStackClosure follow_stack_closure(cm); // Need new claim bits before marking starts. ClassLoaderDataGraph::clear_claimed_marks(); { GCTraceTime tm_m("par mark", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ParallelScavengeHeap::ParStrongRootsScope psrs; GCTaskQueue* q = GCTaskQueue::create(); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles)); // We scan the thread roots in parallel Threads::create_thread_roots_marking_tasks(q); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti)); q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache)); if (active_gc_threads > 1) { for (uint j = 0; j < active_gc_threads; j++) { q->enqueue(new StealMarkingTask(&terminator)); } } gc_task_manager()->execute_and_wait(q); } // Process reference objects found during marking { GCTraceTime tm_r("reference processing", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ReferenceProcessorStats stats; if (ref_processor()->processing_is_mt()) { RefProcTaskExecutor task_executor; stats = ref_processor()->process_discovered_references( is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, &task_executor, &_gc_timer, _gc_tracer.gc_id()); } else { stats = ref_processor()->process_discovered_references( is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL, &_gc_timer, _gc_tracer.gc_id()); } gc_tracer->report_gc_reference_stats(stats); } GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); // This is the point where the entire marking should have completed. assert(cm->marking_stacks_empty(), "Marking should have completed"); // Follow system dictionary roots and unload classes. bool purged_class = SystemDictionary::do_unloading(is_alive_closure()); // Unload nmethods. CodeCache::do_unloading(is_alive_closure(), purged_class); // Prune dead klasses from subklass/sibling/implementor lists. Klass::clean_weak_klass_links(is_alive_closure()); // Delete entries for dead interned strings. StringTable::unlink(is_alive_closure()); // Clean up unreferenced symbols in symbol table. SymbolTable::unlink(); _gc_tracer.report_object_count_after_gc(is_alive_closure()); } void PSParallelCompact::follow_class_loader(ParCompactionManager* cm, ClassLoaderData* cld) { PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm); PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure); cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true); } void PSParallelCompact::adjust_roots() { // Adjust the pointers to reflect the new locations GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); // Need new claim bits when tracing through and adjusting pointers. ClassLoaderDataGraph::clear_claimed_marks(); // General strong roots. Universe::oops_do(adjust_pointer_closure()); JNIHandles::oops_do(adjust_pointer_closure()); // Global (strong) JNI handles CLDToOopClosure adjust_from_cld(adjust_pointer_closure()); Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL); ObjectSynchronizer::oops_do(adjust_pointer_closure()); FlatProfiler::oops_do(adjust_pointer_closure()); Management::oops_do(adjust_pointer_closure()); JvmtiExport::oops_do(adjust_pointer_closure()); SystemDictionary::oops_do(adjust_pointer_closure()); ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true); // Now adjust pointers in remaining weak roots. (All of which should // have been cleared if they pointed to non-surviving objects.) // Global (weak) JNI handles JNIHandles::weak_oops_do(adjust_pointer_closure()); CodeBlobToOopClosure adjust_from_blobs(adjust_pointer_closure(), CodeBlobToOopClosure::FixRelocations); CodeCache::blobs_do(&adjust_from_blobs); StringTable::oops_do(adjust_pointer_closure()); ref_processor()->weak_oops_do(adjust_pointer_closure()); // Roots were visited so references into the young gen in roots // may have been scanned. Process them also. // Should the reference processor have a span that excludes // young gen objects? PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure()); } void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q, uint parallel_gc_threads) { GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); // Find the threads that are active unsigned int which = 0; const uint task_count = MAX2(parallel_gc_threads, 1U); for (uint j = 0; j < task_count; j++) { q->enqueue(new DrainStacksCompactionTask(j)); ParCompactionManager::verify_region_list_empty(j); // Set the region stacks variables to "no" region stack values // so that they will be recognized and needing a region stack // in the stealing tasks if they do not get one by executing // a draining stack. ParCompactionManager* cm = ParCompactionManager::manager_array(j); cm->set_region_stack(NULL); cm->set_region_stack_index((uint)max_uintx); } ParCompactionManager::reset_recycled_stack_index(); // Find all regions that are available (can be filled immediately) and // distribute them to the thread stacks. The iteration is done in reverse // order (high to low) so the regions will be removed in ascending order. const ParallelCompactData& sd = PSParallelCompact::summary_data(); size_t fillable_regions = 0; // A count for diagnostic purposes. // A region index which corresponds to the tasks created above. // "which" must be 0 <= which < task_count which = 0; // id + 1 is used to test termination so unsigned can // be used with an old_space_id == 0. for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) { SpaceInfo* const space_info = _space_info + id; MutableSpace* const space = space_info->space(); HeapWord* const new_top = space_info->new_top(); const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix()); const size_t end_region = sd.addr_to_region_idx(sd.region_align_up(new_top)); for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) { if (sd.region(cur)->claim_unsafe()) { ParCompactionManager::region_list_push(which, cur); if (TraceParallelOldGCCompactionPhase && Verbose) { const size_t count_mod_8 = fillable_regions & 7; if (count_mod_8 == 0) gclog_or_tty->print("fillable: "); gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur); if (count_mod_8 == 7) gclog_or_tty->cr(); } NOT_PRODUCT(++fillable_regions;) // Assign regions to tasks in round-robin fashion. if (++which == task_count) { assert(which <= parallel_gc_threads, "Inconsistent number of workers"); which = 0; } } } } if (TraceParallelOldGCCompactionPhase) { if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr(); gclog_or_tty->print_cr("%u initially fillable regions", fillable_regions); } } #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q, uint parallel_gc_threads) { GCTraceTime tm("dense prefix task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ParallelCompactData& sd = PSParallelCompact::summary_data(); // Iterate over all the spaces adding tasks for updating // regions in the dense prefix. Assume that 1 gc thread // will work on opening the gaps and the remaining gc threads // will work on the dense prefix. unsigned int space_id; for (space_id = old_space_id; space_id < last_space_id; ++ space_id) { HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix(); const MutableSpace* const space = _space_info[space_id].space(); if (dense_prefix_end == space->bottom()) { // There is no dense prefix for this space. continue; } // The dense prefix is before this region. size_t region_index_end_dense_prefix = sd.addr_to_region_idx(dense_prefix_end); RegionData* const dense_prefix_cp = sd.region(region_index_end_dense_prefix); assert(dense_prefix_end == space->end() || dense_prefix_cp->available() || dense_prefix_cp->claimed(), "The region after the dense prefix should always be ready to fill"); size_t region_index_start = sd.addr_to_region_idx(space->bottom()); // Is there dense prefix work? size_t total_dense_prefix_regions = region_index_end_dense_prefix - region_index_start; // How many regions of the dense prefix should be given to // each thread? if (total_dense_prefix_regions > 0) { uint tasks_for_dense_prefix = 1; if (total_dense_prefix_regions <= (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) { // Don't over partition. This assumes that // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value // so there are not many regions to process. tasks_for_dense_prefix = parallel_gc_threads; } else { // Over partition tasks_for_dense_prefix = parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING; } size_t regions_per_thread = total_dense_prefix_regions / tasks_for_dense_prefix; // Give each thread at least 1 region. if (regions_per_thread == 0) { regions_per_thread = 1; } for (uint k = 0; k < tasks_for_dense_prefix; k++) { if (region_index_start >= region_index_end_dense_prefix) { break; } // region_index_end is not processed size_t region_index_end = MIN2(region_index_start + regions_per_thread, region_index_end_dense_prefix); q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id), region_index_start, region_index_end)); region_index_start = region_index_end; } } // This gets any part of the dense prefix that did not // fit evenly. if (region_index_start < region_index_end_dense_prefix) { q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id), region_index_start, region_index_end_dense_prefix)); } } } void PSParallelCompact::enqueue_region_stealing_tasks( GCTaskQueue* q, ParallelTaskTerminator* terminator_ptr, uint parallel_gc_threads) { GCTraceTime tm("steal task setup", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); // Once a thread has drained it's stack, it should try to steal regions from // other threads. if (parallel_gc_threads > 1) { for (uint j = 0; j < parallel_gc_threads; j++) { q->enqueue(new StealRegionCompactionTask(terminator_ptr)); } } } #ifdef ASSERT // Write a histogram of the number of times the block table was filled for a // region. void PSParallelCompact::write_block_fill_histogram(outputStream* const out) { if (!TraceParallelOldGCCompactionPhase) return; typedef ParallelCompactData::RegionData rd_t; ParallelCompactData& sd = summary_data(); for (unsigned int id = old_space_id; id < last_space_id; ++id) { MutableSpace* const spc = _space_info[id].space(); if (spc->bottom() != spc->top()) { const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom()); HeapWord* const top_aligned_up = sd.region_align_up(spc->top()); const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up); size_t histo[5] = { 0, 0, 0, 0, 0 }; const size_t histo_len = sizeof(histo) / sizeof(size_t); const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t)); for (const rd_t* cur = beg; cur < end; ++cur) { ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)]; } out->print("%u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt); for (size_t i = 0; i < histo_len; ++i) { out->print(" " SIZE_FORMAT_W(5) " %5.1f%%", histo[i], 100.0 * histo[i] / region_cnt); } out->cr(); } } } #endif // #ifdef ASSERT void PSParallelCompact::compact() { // trace("5"); GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); PSOldGen* old_gen = heap->old_gen(); old_gen->start_array()->reset(); uint parallel_gc_threads = heap->gc_task_manager()->workers(); uint active_gc_threads = heap->gc_task_manager()->active_workers(); TaskQueueSetSuper* qset = ParCompactionManager::region_array(); ParallelTaskTerminator terminator(active_gc_threads, qset); GCTaskQueue* q = GCTaskQueue::create(); enqueue_region_draining_tasks(q, active_gc_threads); enqueue_dense_prefix_tasks(q, active_gc_threads); enqueue_region_stealing_tasks(q, &terminator, active_gc_threads); { GCTraceTime tm_pc("par compact", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); gc_task_manager()->execute_and_wait(q); #ifdef ASSERT // Verify that all regions have been processed before the deferred updates. for (unsigned int id = old_space_id; id < last_space_id; ++id) { verify_complete(SpaceId(id)); } #endif } { // Update the deferred objects, if any. Any compaction manager can be used. GCTraceTime tm_du("deferred updates", print_phases(), true, &_gc_timer, _gc_tracer.gc_id()); ParCompactionManager* cm = ParCompactionManager::manager_array(0); for (unsigned int id = old_space_id; id < last_space_id; ++id) { update_deferred_objects(cm, SpaceId(id)); } } DEBUG_ONLY(write_block_fill_histogram(gclog_or_tty)); } #ifdef ASSERT void PSParallelCompact::verify_complete(SpaceId space_id) { // All Regions between space bottom() to new_top() should be marked as filled // and all Regions between new_top() and top() should be available (i.e., // should have been emptied). ParallelCompactData& sd = summary_data(); SpaceInfo si = _space_info[space_id]; HeapWord* new_top_addr = sd.region_align_up(si.new_top()); HeapWord* old_top_addr = sd.region_align_up(si.space()->top()); const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom()); const size_t new_top_region = sd.addr_to_region_idx(new_top_addr); const size_t old_top_region = sd.addr_to_region_idx(old_top_addr); bool issued_a_warning = false; size_t cur_region; for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) { const RegionData* const c = sd.region(cur_region); if (!c->completed()) { warning("region " SIZE_FORMAT " not filled: " "destination_count=" SIZE_FORMAT, cur_region, c->destination_count()); issued_a_warning = true; } } for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) { const RegionData* const c = sd.region(cur_region); if (!c->available()) { warning("region " SIZE_FORMAT " not empty: " "destination_count=" SIZE_FORMAT, cur_region, c->destination_count()); issued_a_warning = true; } } if (issued_a_warning) { print_region_ranges(); } } #endif // #ifdef ASSERT // Update interior oops in the ranges of regions [beg_region, end_region). void PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm, SpaceId space_id, size_t beg_region, size_t end_region) { ParallelCompactData& sd = summary_data(); ParMarkBitMap* const mbm = mark_bitmap(); HeapWord* beg_addr = sd.region_to_addr(beg_region); HeapWord* const end_addr = sd.region_to_addr(end_region); assert(beg_region <= end_region, "bad region range"); assert(end_addr <= dense_prefix(space_id), "not in the dense prefix"); #ifdef ASSERT // Claim the regions to avoid triggering an assert when they are marked as // filled. for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) { assert(sd.region(claim_region)->claim_unsafe(), "claim() failed"); } #endif // #ifdef ASSERT if (beg_addr != space(space_id)->bottom()) { // Find the first live object or block of dead space that *starts* in this // range of regions. If a partial object crosses onto the region, skip it; // it will be marked for 'deferred update' when the object head is // processed. If dead space crosses onto the region, it is also skipped; it // will be filled when the prior region is processed. If neither of those // apply, the first word in the region is the start of a live object or dead // space. assert(beg_addr > space(space_id)->bottom(), "sanity"); const RegionData* const cp = sd.region(beg_region); if (cp->partial_obj_size() != 0) { beg_addr = sd.partial_obj_end(beg_region); } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) { beg_addr = mbm->find_obj_beg(beg_addr, end_addr); } } if (beg_addr < end_addr) { // A live object or block of dead space starts in this range of Regions. HeapWord* const dense_prefix_end = dense_prefix(space_id); // Create closures and iterate. UpdateOnlyClosure update_closure(mbm, cm, space_id); FillClosure fill_closure(cm, space_id); ParMarkBitMap::IterationStatus status; status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr, dense_prefix_end); if (status == ParMarkBitMap::incomplete) { update_closure.do_addr(update_closure.source()); } } // Mark the regions as filled. RegionData* const beg_cp = sd.region(beg_region); RegionData* const end_cp = sd.region(end_region); for (RegionData* cp = beg_cp; cp < end_cp; ++cp) { cp->set_completed(); } } // Return the SpaceId for the space containing addr. If addr is not in the // heap, last_space_id is returned. In debug mode it expects the address to be // in the heap and asserts such. PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) { assert(Universe::heap()->is_in_reserved(addr), "addr not in the heap"); for (unsigned int id = old_space_id; id < last_space_id; ++id) { if (_space_info[id].space()->contains(addr)) { return SpaceId(id); } } assert(false, "no space contains the addr"); return last_space_id; } void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm, SpaceId id) { assert(id < last_space_id, "bad space id"); ParallelCompactData& sd = summary_data(); const SpaceInfo* const space_info = _space_info + id; ObjectStartArray* const start_array = space_info->start_array(); const MutableSpace* const space = space_info->space(); assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set"); HeapWord* const beg_addr = space_info->dense_prefix(); HeapWord* const end_addr = sd.region_align_up(space_info->new_top()); const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr); const RegionData* const end_region = sd.addr_to_region_ptr(end_addr); const RegionData* cur_region; for (cur_region = beg_region; cur_region < end_region; ++cur_region) { HeapWord* const addr = cur_region->deferred_obj_addr(); if (addr != NULL) { if (start_array != NULL) { start_array->allocate_block(addr); } oop(addr)->update_contents(cm); assert(oop(addr)->is_oop_or_null(), "should be an oop now"); } } } // Skip over count live words starting from beg, and return the address of the // next live word. Unless marked, the word corresponding to beg is assumed to // be dead. Callers must either ensure beg does not correspond to the middle of // an object, or account for those live words in some other way. Callers must // also ensure that there are enough live words in the range [beg, end) to skip. HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count) { assert(count > 0, "sanity"); ParMarkBitMap* m = mark_bitmap(); idx_t bits_to_skip = m->words_to_bits(count); idx_t cur_beg = m->addr_to_bit(beg); const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end)); do { cur_beg = m->find_obj_beg(cur_beg, search_end); idx_t cur_end = m->find_obj_end(cur_beg, search_end); const size_t obj_bits = cur_end - cur_beg + 1; if (obj_bits > bits_to_skip) { return m->bit_to_addr(cur_beg + bits_to_skip); } bits_to_skip -= obj_bits; cur_beg = cur_end + 1; } while (bits_to_skip > 0); // Skipping the desired number of words landed just past the end of an object. // Find the start of the next object. cur_beg = m->find_obj_beg(cur_beg, search_end); assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip"); return m->bit_to_addr(cur_beg); } HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr, SpaceId src_space_id, size_t src_region_idx) { assert(summary_data().is_region_aligned(dest_addr), "not aligned"); const SplitInfo& split_info = _space_info[src_space_id].split_info(); if (split_info.dest_region_addr() == dest_addr) { // The partial object ending at the split point contains the first word to // be copied to dest_addr. return split_info.first_src_addr(); } const ParallelCompactData& sd = summary_data(); ParMarkBitMap* const bitmap = mark_bitmap(); const size_t RegionSize = ParallelCompactData::RegionSize; assert(sd.is_region_aligned(dest_addr), "not aligned"); const RegionData* const src_region_ptr = sd.region(src_region_idx); const size_t partial_obj_size = src_region_ptr->partial_obj_size(); HeapWord* const src_region_destination = src_region_ptr->destination(); assert(dest_addr >= src_region_destination, "wrong src region"); assert(src_region_ptr->data_size() > 0, "src region cannot be empty"); HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx); HeapWord* const src_region_end = src_region_beg + RegionSize; HeapWord* addr = src_region_beg; if (dest_addr == src_region_destination) { // Return the first live word in the source region. if (partial_obj_size == 0) { addr = bitmap->find_obj_beg(addr, src_region_end); assert(addr < src_region_end, "no objects start in src region"); } return addr; } // Must skip some live data. size_t words_to_skip = dest_addr - src_region_destination; assert(src_region_ptr->data_size() > words_to_skip, "wrong src region"); if (partial_obj_size >= words_to_skip) { // All the live words to skip are part of the partial object. addr += words_to_skip; if (partial_obj_size == words_to_skip) { // Find the first live word past the partial object. addr = bitmap->find_obj_beg(addr, src_region_end); assert(addr < src_region_end, "wrong src region"); } return addr; } // Skip over the partial object (if any). if (partial_obj_size != 0) { words_to_skip -= partial_obj_size; addr += partial_obj_size; } // Skip over live words due to objects that start in the region. addr = skip_live_words(addr, src_region_end, words_to_skip); assert(addr < src_region_end, "wrong src region"); return addr; } void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm, SpaceId src_space_id, size_t beg_region, HeapWord* end_addr) { ParallelCompactData& sd = summary_data(); #ifdef ASSERT MutableSpace* const src_space = _space_info[src_space_id].space(); HeapWord* const beg_addr = sd.region_to_addr(beg_region); assert(src_space->contains(beg_addr) || beg_addr == src_space->end(), "src_space_id does not match beg_addr"); assert(src_space->contains(end_addr) || end_addr == src_space->end(), "src_space_id does not match end_addr"); #endif // #ifdef ASSERT RegionData* const beg = sd.region(beg_region); RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr)); // Regions up to new_top() are enqueued if they become available. HeapWord* const new_top = _space_info[src_space_id].new_top(); RegionData* const enqueue_end = sd.addr_to_region_ptr(sd.region_align_up(new_top)); for (RegionData* cur = beg; cur < end; ++cur) { assert(cur->data_size() > 0, "region must have live data"); cur->decrement_destination_count(); if (cur < enqueue_end && cur->available() && cur->claim()) { cm->push_region(sd.region(cur)); } } } size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure, SpaceId& src_space_id, HeapWord*& src_space_top, HeapWord* end_addr) { typedef ParallelCompactData::RegionData RegionData; ParallelCompactData& sd = PSParallelCompact::summary_data(); const size_t region_size = ParallelCompactData::RegionSize; size_t src_region_idx = 0; // Skip empty regions (if any) up to the top of the space. HeapWord* const src_aligned_up = sd.region_align_up(end_addr); RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up); HeapWord* const top_aligned_up = sd.region_align_up(src_space_top); const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up); while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) { ++src_region_ptr; } if (src_region_ptr < top_region_ptr) { // The next source region is in the current space. Update src_region_idx // and the source address to match src_region_ptr. src_region_idx = sd.region(src_region_ptr); HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx); if (src_region_addr > closure.source()) { closure.set_source(src_region_addr); } return src_region_idx; } // Switch to a new source space and find the first non-empty region. unsigned int space_id = src_space_id + 1; assert(space_id < last_space_id, "not enough spaces"); HeapWord* const destination = closure.destination(); do { MutableSpace* space = _space_info[space_id].space(); HeapWord* const bottom = space->bottom(); const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom); // Iterate over the spaces that do not compact into themselves. if (bottom_cp->destination() != bottom) { HeapWord* const top_aligned_up = sd.region_align_up(space->top()); const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up); for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) { if (src_cp->live_obj_size() > 0) { // Found it. assert(src_cp->destination() == destination, "first live obj in the space must match the destination"); assert(src_cp->partial_obj_size() == 0, "a space cannot begin with a partial obj"); src_space_id = SpaceId(space_id); src_space_top = space->top(); const size_t src_region_idx = sd.region(src_cp); closure.set_source(sd.region_to_addr(src_region_idx)); return src_region_idx; } else { assert(src_cp->data_size() == 0, "sanity"); } } } } while (++space_id < last_space_id); assert(false, "no source region was found"); return 0; } void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx) { typedef ParMarkBitMap::IterationStatus IterationStatus; const size_t RegionSize = ParallelCompactData::RegionSize; ParMarkBitMap* const bitmap = mark_bitmap(); ParallelCompactData& sd = summary_data(); RegionData* const region_ptr = sd.region(region_idx); // Get the items needed to construct the closure. HeapWord* dest_addr = sd.region_to_addr(region_idx); SpaceId dest_space_id = space_id(dest_addr); ObjectStartArray* start_array = _space_info[dest_space_id].start_array(); HeapWord* new_top = _space_info[dest_space_id].new_top(); assert(dest_addr < new_top, "sanity"); const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize); // Get the source region and related info. size_t src_region_idx = region_ptr->source_region(); SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx)); HeapWord* src_space_top = _space_info[src_space_id].space()->top(); MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words); closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx)); // Adjust src_region_idx to prepare for decrementing destination counts (the // destination count is not decremented when a region is copied to itself). if (src_region_idx == region_idx) { src_region_idx += 1; } if (bitmap->is_unmarked(closure.source())) { // The first source word is in the middle of an object; copy the remainder // of the object or as much as will fit. The fact that pointer updates were // deferred will be noted when the object header is processed. HeapWord* const old_src_addr = closure.source(); closure.copy_partial_obj(); if (closure.is_full()) { decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source()); region_ptr->set_deferred_obj_addr(NULL); region_ptr->set_completed(); return; } HeapWord* const end_addr = sd.region_align_down(closure.source()); if (sd.region_align_down(old_src_addr) != end_addr) { // The partial object was copied from more than one source region. decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr); // Move to the next source region, possibly switching spaces as well. All // args except end_addr may be modified. src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr); } } do { HeapWord* const cur_addr = closure.source(); HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1), src_space_top); IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr); if (status == ParMarkBitMap::incomplete) { // The last obj that starts in the source region does not end in the // region. assert(closure.source() < end_addr, "sanity"); HeapWord* const obj_beg = closure.source(); HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(), src_space_top); HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end); if (obj_end < range_end) { // The end was found; the entire object will fit. status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end)); assert(status != ParMarkBitMap::would_overflow, "sanity"); } else { // The end was not found; the object will not fit. assert(range_end < src_space_top, "obj cannot cross space boundary"); status = ParMarkBitMap::would_overflow; } } if (status == ParMarkBitMap::would_overflow) { // The last object did not fit. Note that interior oop updates were // deferred, then copy enough of the object to fill the region. region_ptr->set_deferred_obj_addr(closure.destination()); status = closure.copy_until_full(); // copies from closure.source() decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source()); region_ptr->set_completed(); return; } if (status == ParMarkBitMap::full) { decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source()); region_ptr->set_deferred_obj_addr(NULL); region_ptr->set_completed(); return; } decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr); // Move to the next source region, possibly switching spaces as well. All // args except end_addr may be modified. src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr); } while (true); } void PSParallelCompact::fill_blocks(size_t region_idx) { // Fill in the block table elements for the specified region. Each block // table element holds the number of live words in the region that are to the // left of the first object that starts in the block. Thus only blocks in // which an object starts need to be filled. // // The algorithm scans the section of the bitmap that corresponds to the // region, keeping a running total of the live words. When an object start is // found, if it's the first to start in the block that contains it, the // current total is written to the block table element. const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize; const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize; const size_t RegionSize = ParallelCompactData::RegionSize; ParallelCompactData& sd = summary_data(); const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size(); if (partial_obj_size >= RegionSize) { return; // No objects start in this region. } // Ensure the first loop iteration decides that the block has changed. size_t cur_block = sd.block_count(); const ParMarkBitMap* const bitmap = mark_bitmap(); const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment; assert((size_t)1 << Log2BitsPerBlock == bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity"); size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize); const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize); size_t live_bits = bitmap->words_to_bits(partial_obj_size); beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end); while (beg_bit < range_end) { const size_t new_block = beg_bit >> Log2BitsPerBlock; if (new_block != cur_block) { cur_block = new_block; sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits)); } const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end); if (end_bit < range_end - 1) { live_bits += end_bit - beg_bit + 1; beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end); } else { return; } } } void PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) { const MutableSpace* sp = space(space_id); if (sp->is_empty()) { return; } ParallelCompactData& sd = PSParallelCompact::summary_data(); ParMarkBitMap* const bitmap = mark_bitmap(); HeapWord* const dp_addr = dense_prefix(space_id); HeapWord* beg_addr = sp->bottom(); HeapWord* end_addr = sp->top(); assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix"); const size_t beg_region = sd.addr_to_region_idx(beg_addr); const size_t dp_region = sd.addr_to_region_idx(dp_addr); if (beg_region < dp_region) { update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region); } // The destination of the first live object that starts in the region is one // past the end of the partial object entering the region (if any). HeapWord* const dest_addr = sd.partial_obj_end(dp_region); HeapWord* const new_top = _space_info[space_id].new_top(); assert(new_top >= dest_addr, "bad new_top value"); const size_t words = pointer_delta(new_top, dest_addr); if (words > 0) { ObjectStartArray* start_array = _space_info[space_id].start_array(); MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words); ParMarkBitMap::IterationStatus status; status = bitmap->iterate(&closure, dest_addr, end_addr); assert(status == ParMarkBitMap::full, "iteration not complete"); assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr, "live objects skipped because closure is full"); } } jlong PSParallelCompact::millis_since_last_gc() { // We need a monotonically non-deccreasing time in ms but // os::javaTimeMillis() does not guarantee monotonicity. jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; jlong ret_val = now - _time_of_last_gc; // XXX See note in genCollectedHeap::millis_since_last_gc(). if (ret_val < 0) { NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);) return 0; } return ret_val; } void PSParallelCompact::reset_millis_since_last_gc() { // We need a monotonically non-deccreasing time in ms but // os::javaTimeMillis() does not guarantee monotonicity. _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; } ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full() { if (source() != destination()) { DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());) Copy::aligned_conjoint_words(source(), destination(), words_remaining()); } update_state(words_remaining()); assert(is_full(), "sanity"); return ParMarkBitMap::full; } void MoveAndUpdateClosure::copy_partial_obj() { size_t words = words_remaining(); HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end()); HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end); if (end_addr < range_end) { words = bitmap()->obj_size(source(), end_addr); } // This test is necessary; if omitted, the pointer updates to a partial object // that crosses the dense prefix boundary could be overwritten. if (source() != destination()) { DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());) Copy::aligned_conjoint_words(source(), destination(), words); } update_state(words); } ParMarkBitMapClosure::IterationStatus MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) { assert(destination() != NULL, "sanity"); assert(bitmap()->obj_size(addr) == words, "bad size"); _source = addr; assert(PSParallelCompact::summary_data().calc_new_pointer(source()) == destination(), "wrong destination"); if (words > words_remaining()) { return ParMarkBitMap::would_overflow; } // The start_array must be updated even if the object is not moving. if (_start_array != NULL) { _start_array->allocate_block(destination()); } if (destination() != source()) { DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());) Copy::aligned_conjoint_words(source(), destination(), words); } oop moved_oop = (oop) destination(); moved_oop->update_contents(compaction_manager()); assert(moved_oop->is_oop_or_null(), "Object should be whole at this point"); update_state(words); assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity"); return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete; } UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm, ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) : ParMarkBitMapClosure(mbm, cm), _space_id(space_id), _start_array(PSParallelCompact::start_array(space_id)) { } // Updates the references in the object to their new values. ParMarkBitMapClosure::IterationStatus UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) { do_addr(addr); return ParMarkBitMap::incomplete; }