/* * Copyright (c) 2001, 2013, 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 "gc_implementation/shared/adaptiveSizePolicy.hpp" #include "gc_implementation/shared/gcPolicyCounters.hpp" #include "gc_implementation/shared/vmGCOperations.hpp" #include "memory/cardTableRS.hpp" #include "memory/collectorPolicy.hpp" #include "memory/gcLocker.inline.hpp" #include "memory/genCollectedHeap.hpp" #include "memory/generationSpec.hpp" #include "memory/space.hpp" #include "memory/universe.hpp" #include "runtime/arguments.hpp" #include "runtime/globals_extension.hpp" #include "runtime/handles.inline.hpp" #include "runtime/java.hpp" #include "runtime/thread.inline.hpp" #include "runtime/vmThread.hpp" #include "utilities/macros.hpp" #if INCLUDE_ALL_GCS #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp" #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp" #endif // INCLUDE_ALL_GCS // CollectorPolicy methods. // Align down. If the aligning result in 0, return 'alignment'. static size_t restricted_align_down(size_t size, size_t alignment) { return MAX2(alignment, align_size_down_(size, alignment)); } void CollectorPolicy::initialize_flags() { assert(max_alignment() >= min_alignment(), err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT, max_alignment(), min_alignment())); assert(max_alignment() % min_alignment() == 0, err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT, max_alignment(), min_alignment())); if (MaxHeapSize < InitialHeapSize) { vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified"); } // Do not use FLAG_SET_ERGO to update MaxMetaspaceSize, since this will // override if MaxMetaspaceSize was set on the command line or not. // This information is needed later to conform to the specification of the // java.lang.management.MemoryUsage API. // // Ideally, we would be able to set the default value of MaxMetaspaceSize in // globals.hpp to the aligned value, but this is not possible, since the // alignment depends on other flags being parsed. MaxMetaspaceSize = restricted_align_down(MaxMetaspaceSize, max_alignment()); if (MetaspaceSize > MaxMetaspaceSize) { MetaspaceSize = MaxMetaspaceSize; } MetaspaceSize = restricted_align_down(MetaspaceSize, min_alignment()); assert(MetaspaceSize <= MaxMetaspaceSize, "Must be"); MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, min_alignment()); MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, min_alignment()); MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment()); assert(MetaspaceSize % min_alignment() == 0, "metapace alignment"); assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment"); if (MetaspaceSize < 256*K) { vm_exit_during_initialization("Too small initial Metaspace size"); } } void CollectorPolicy::initialize_size_info() { // User inputs from -mx and ms must be aligned set_min_heap_byte_size(align_size_up(Arguments::min_heap_size(), min_alignment())); set_initial_heap_byte_size(align_size_up(InitialHeapSize, min_alignment())); set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment())); // Check heap parameter properties if (initial_heap_byte_size() < M) { vm_exit_during_initialization("Too small initial heap"); } // Check heap parameter properties if (min_heap_byte_size() < M) { vm_exit_during_initialization("Too small minimum heap"); } if (initial_heap_byte_size() <= NewSize) { // make sure there is at least some room in old space vm_exit_during_initialization("Too small initial heap for new size specified"); } if (max_heap_byte_size() < min_heap_byte_size()) { vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified"); } if (initial_heap_byte_size() < min_heap_byte_size()) { vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified"); } if (max_heap_byte_size() < initial_heap_byte_size()) { vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified"); } if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap " SIZE_FORMAT " Maximum heap " SIZE_FORMAT, min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size()); } } bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) { bool result = _should_clear_all_soft_refs; set_should_clear_all_soft_refs(false); return result; } GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap, int max_covered_regions) { switch (rem_set_name()) { case GenRemSet::CardTable: { CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions); return res; } default: guarantee(false, "unrecognized GenRemSet::Name"); return NULL; } } void CollectorPolicy::cleared_all_soft_refs() { // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may // have been cleared in the last collection but if the gc overhear // limit continues to be near, SoftRefs should still be cleared. if (size_policy() != NULL) { _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near(); } _all_soft_refs_clear = true; } size_t CollectorPolicy::compute_max_alignment() { // The card marking array and the offset arrays for old generations are // committed in os pages as well. Make sure they are entirely full (to // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1 // byte entry and the os page size is 4096, the maximum heap size should // be 512*4096 = 2MB aligned. // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable // is supported. // Requirements of any new remembered set implementations must be added here. size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable); // Parallel GC does its own alignment of the generations to avoid requiring a // large page (256M on some platforms) for the permanent generation. The // other collectors should also be updated to do their own alignment and then // this use of lcm() should be removed. if (UseLargePages && !UseParallelGC) { // in presence of large pages we have to make sure that our // alignment is large page aware alignment = lcm(os::large_page_size(), alignment); } return alignment; } // GenCollectorPolicy methods. size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) { size_t x = base_size / (NewRatio+1); size_t new_gen_size = x > min_alignment() ? align_size_down(x, min_alignment()) : min_alignment(); return new_gen_size; } size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size, size_t maximum_size) { size_t alignment = min_alignment(); size_t max_minus = maximum_size - alignment; return desired_size < max_minus ? desired_size : max_minus; } void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size, size_t init_promo_size, size_t init_survivor_size) { const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0; _size_policy = new AdaptiveSizePolicy(init_eden_size, init_promo_size, init_survivor_size, max_gc_pause_sec, GCTimeRatio); } void GenCollectorPolicy::initialize_flags() { // All sizes must be multiples of the generation granularity. set_min_alignment((uintx) Generation::GenGrain); set_max_alignment(compute_max_alignment()); CollectorPolicy::initialize_flags(); // All generational heaps have a youngest gen; handle those flags here. // Adjust max size parameters if (NewSize > MaxNewSize) { MaxNewSize = NewSize; } NewSize = align_size_down(NewSize, min_alignment()); MaxNewSize = align_size_down(MaxNewSize, min_alignment()); // Check validity of heap flags assert(NewSize % min_alignment() == 0, "eden space alignment"); assert(MaxNewSize % min_alignment() == 0, "survivor space alignment"); if (NewSize < 3*min_alignment()) { // make sure there room for eden and two survivor spaces vm_exit_during_initialization("Too small new size specified"); } if (SurvivorRatio < 1 || NewRatio < 1) { vm_exit_during_initialization("Invalid heap ratio specified"); } } void TwoGenerationCollectorPolicy::initialize_flags() { GenCollectorPolicy::initialize_flags(); OldSize = align_size_down(OldSize, min_alignment()); if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) { // NewRatio will be used later to set the young generation size so we use // it to calculate how big the heap should be based on the requested OldSize // and NewRatio. assert(NewRatio > 0, "NewRatio should have been set up earlier"); size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1); calculated_heapsize = align_size_up(calculated_heapsize, max_alignment()); MaxHeapSize = calculated_heapsize; InitialHeapSize = calculated_heapsize; } MaxHeapSize = align_size_up(MaxHeapSize, max_alignment()); // adjust max heap size if necessary if (NewSize + OldSize > MaxHeapSize) { if (FLAG_IS_CMDLINE(MaxHeapSize)) { // somebody set a maximum heap size with the intention that we should not // exceed it. Adjust New/OldSize as necessary. uintx calculated_size = NewSize + OldSize; double shrink_factor = (double) MaxHeapSize / calculated_size; // align NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment()); // OldSize is already aligned because above we aligned MaxHeapSize to // max_alignment(), and we just made sure that NewSize is aligned to // min_alignment(). In initialize_flags() we verified that max_alignment() // is a multiple of min_alignment(). OldSize = MaxHeapSize - NewSize; } else { MaxHeapSize = NewSize + OldSize; } } // need to do this again MaxHeapSize = align_size_up(MaxHeapSize, max_alignment()); // adjust max heap size if necessary if (NewSize + OldSize > MaxHeapSize) { if (FLAG_IS_CMDLINE(MaxHeapSize)) { // somebody set a maximum heap size with the intention that we should not // exceed it. Adjust New/OldSize as necessary. uintx calculated_size = NewSize + OldSize; double shrink_factor = (double) MaxHeapSize / calculated_size; // align NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment()); // OldSize is already aligned because above we aligned MaxHeapSize to // max_alignment(), and we just made sure that NewSize is aligned to // min_alignment(). In initialize_flags() we verified that max_alignment() // is a multiple of min_alignment(). OldSize = MaxHeapSize - NewSize; } else { MaxHeapSize = NewSize + OldSize; } } // need to do this again MaxHeapSize = align_size_up(MaxHeapSize, max_alignment()); always_do_update_barrier = UseConcMarkSweepGC; // Check validity of heap flags assert(OldSize % min_alignment() == 0, "old space alignment"); assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment"); } // Values set on the command line win over any ergonomically // set command line parameters. // Ergonomic choice of parameters are done before this // method is called. Values for command line parameters such as NewSize // and MaxNewSize feed those ergonomic choices into this method. // This method makes the final generation sizings consistent with // themselves and with overall heap sizings. // In the absence of explicitly set command line flags, policies // such as the use of NewRatio are used to size the generation. void GenCollectorPolicy::initialize_size_info() { CollectorPolicy::initialize_size_info(); // min_alignment() is used for alignment within a generation. // There is additional alignment done down stream for some // collectors that sometimes causes unwanted rounding up of // generations sizes. // Determine maximum size of gen0 size_t max_new_size = 0; if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) { if (MaxNewSize < min_alignment()) { max_new_size = min_alignment(); } if (MaxNewSize >= max_heap_byte_size()) { max_new_size = align_size_down(max_heap_byte_size() - min_alignment(), min_alignment()); warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or " "greater than the entire heap (" SIZE_FORMAT "k). A " "new generation size of " SIZE_FORMAT "k will be used.", MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K); } else { max_new_size = align_size_down(MaxNewSize, min_alignment()); } // The case for FLAG_IS_ERGO(MaxNewSize) could be treated // specially at this point to just use an ergonomically set // MaxNewSize to set max_new_size. For cases with small // heaps such a policy often did not work because the MaxNewSize // was larger than the entire heap. The interpretation given // to ergonomically set flags is that the flags are set // by different collectors for their own special needs but // are not allowed to badly shape the heap. This allows the // different collectors to decide what's best for themselves // without having to factor in the overall heap shape. It // can be the case in the future that the collectors would // only make "wise" ergonomics choices and this policy could // just accept those choices. The choices currently made are // not always "wise". } else { max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size()); // Bound the maximum size by NewSize below (since it historically // would have been NewSize and because the NewRatio calculation could // yield a size that is too small) and bound it by MaxNewSize above. // Ergonomics plays here by previously calculating the desired // NewSize and MaxNewSize. max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize); } assert(max_new_size > 0, "All paths should set max_new_size"); // Given the maximum gen0 size, determine the initial and // minimum gen0 sizes. if (max_heap_byte_size() == min_heap_byte_size()) { // The maximum and minimum heap sizes are the same so // the generations minimum and initial must be the // same as its maximum. set_min_gen0_size(max_new_size); set_initial_gen0_size(max_new_size); set_max_gen0_size(max_new_size); } else { size_t desired_new_size = 0; if (!FLAG_IS_DEFAULT(NewSize)) { // If NewSize is set ergonomically (for example by cms), it // would make sense to use it. If it is used, also use it // to set the initial size. Although there is no reason // the minimum size and the initial size have to be the same, // the current implementation gets into trouble during the calculation // of the tenured generation sizes if they are different. // Note that this makes the initial size and the minimum size // generally small compared to the NewRatio calculation. _min_gen0_size = NewSize; desired_new_size = NewSize; max_new_size = MAX2(max_new_size, NewSize); } else { // For the case where NewSize is the default, use NewRatio // to size the minimum and initial generation sizes. // Use the default NewSize as the floor for these values. If // NewRatio is overly large, the resulting sizes can be too // small. _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()), NewSize); desired_new_size = MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()), NewSize); } assert(_min_gen0_size > 0, "Sanity check"); set_initial_gen0_size(desired_new_size); set_max_gen0_size(max_new_size); // At this point the desirable initial and minimum sizes have been // determined without regard to the maximum sizes. // Bound the sizes by the corresponding overall heap sizes. set_min_gen0_size( bound_minus_alignment(_min_gen0_size, min_heap_byte_size())); set_initial_gen0_size( bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size())); set_max_gen0_size( bound_minus_alignment(_max_gen0_size, max_heap_byte_size())); // At this point all three sizes have been checked against the // maximum sizes but have not been checked for consistency // among the three. // Final check min <= initial <= max set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size)); set_initial_gen0_size( MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size)); set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size)); } if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 " SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, min_gen0_size(), initial_gen0_size(), max_gen0_size()); } } // Call this method during the sizing of the gen1 to make // adjustments to gen0 because of gen1 sizing policy. gen0 initially has // the most freedom in sizing because it is done before the // policy for gen1 is applied. Once gen1 policies have been applied, // there may be conflicts in the shape of the heap and this method // is used to make the needed adjustments. The application of the // policies could be more sophisticated (iterative for example) but // keeping it simple also seems a worthwhile goal. bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr, size_t* gen1_size_ptr, const size_t heap_size, const size_t min_gen1_size) { bool result = false; if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) { if ((heap_size < (*gen0_size_ptr + min_gen1_size)) && (heap_size >= min_gen1_size + min_alignment())) { // Adjust gen0 down to accommodate min_gen1_size *gen0_size_ptr = heap_size - min_gen1_size; *gen0_size_ptr = MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()), min_alignment()); assert(*gen0_size_ptr > 0, "Min gen0 is too large"); result = true; } else { *gen1_size_ptr = heap_size - *gen0_size_ptr; *gen1_size_ptr = MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()), min_alignment()); } } return result; } // Minimum sizes of the generations may be different than // the initial sizes. An inconsistently is permitted here // in the total size that can be specified explicitly by // command line specification of OldSize and NewSize and // also a command line specification of -Xms. Issue a warning // but allow the values to pass. void TwoGenerationCollectorPolicy::initialize_size_info() { GenCollectorPolicy::initialize_size_info(); // At this point the minimum, initial and maximum sizes // of the overall heap and of gen0 have been determined. // The maximum gen1 size can be determined from the maximum gen0 // and maximum heap size since no explicit flags exits // for setting the gen1 maximum. _max_gen1_size = max_heap_byte_size() - _max_gen0_size; _max_gen1_size = MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()), min_alignment()); // If no explicit command line flag has been set for the // gen1 size, use what is left for gen1. if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) { // The user has not specified any value or ergonomics // has chosen a value (which may or may not be consistent // with the overall heap size). In either case make // the minimum, maximum and initial sizes consistent // with the gen0 sizes and the overall heap sizes. assert(min_heap_byte_size() > _min_gen0_size, "gen0 has an unexpected minimum size"); set_min_gen1_size(min_heap_byte_size() - min_gen0_size()); set_min_gen1_size( MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()), min_alignment())); set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size()); set_initial_gen1_size( MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()), min_alignment())); } else { // It's been explicitly set on the command line. Use the // OldSize and then determine the consequences. set_min_gen1_size(OldSize); set_initial_gen1_size(OldSize); // If the user has explicitly set an OldSize that is inconsistent // with other command line flags, issue a warning. // The generation minimums and the overall heap mimimum should // be within one heap alignment. if ((_min_gen1_size + _min_gen0_size + min_alignment()) < min_heap_byte_size()) { warning("Inconsistency between minimum heap size and minimum " "generation sizes: using minimum heap = " SIZE_FORMAT, min_heap_byte_size()); } if ((OldSize > _max_gen1_size)) { warning("Inconsistency between maximum heap size and maximum " "generation sizes: using maximum heap = " SIZE_FORMAT " -XX:OldSize flag is being ignored", max_heap_byte_size()); } // If there is an inconsistency between the OldSize and the minimum and/or // initial size of gen0, since OldSize was explicitly set, OldSize wins. if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, min_heap_byte_size(), OldSize)) { if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 " SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, min_gen0_size(), initial_gen0_size(), max_gen0_size()); } } // Initial size if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size, initial_heap_byte_size(), OldSize)) { if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 " SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, min_gen0_size(), initial_gen0_size(), max_gen0_size()); } } } // Enforce the maximum gen1 size. set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size)); // Check that min gen1 <= initial gen1 <= max gen1 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size)); set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size)); if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 " SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT, min_gen1_size(), initial_gen1_size(), max_gen1_size()); } } HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size, bool is_tlab, bool* gc_overhead_limit_was_exceeded) { GenCollectedHeap *gch = GenCollectedHeap::heap(); debug_only(gch->check_for_valid_allocation_state()); assert(gch->no_gc_in_progress(), "Allocation during gc not allowed"); // In general gc_overhead_limit_was_exceeded should be false so // set it so here and reset it to true only if the gc time // limit is being exceeded as checked below. *gc_overhead_limit_was_exceeded = false; HeapWord* result = NULL; // Loop until the allocation is satisified, // or unsatisfied after GC. for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) { HandleMark hm; // discard any handles allocated in each iteration // First allocation attempt is lock-free. Generation *gen0 = gch->get_gen(0); assert(gen0->supports_inline_contig_alloc(), "Otherwise, must do alloc within heap lock"); if (gen0->should_allocate(size, is_tlab)) { result = gen0->par_allocate(size, is_tlab); if (result != NULL) { assert(gch->is_in_reserved(result), "result not in heap"); return result; } } unsigned int gc_count_before; // read inside the Heap_lock locked region { MutexLocker ml(Heap_lock); if (PrintGC && Verbose) { gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:" " attempting locked slow path allocation"); } // Note that only large objects get a shot at being // allocated in later generations. bool first_only = ! should_try_older_generation_allocation(size); result = gch->attempt_allocation(size, is_tlab, first_only); if (result != NULL) { assert(gch->is_in_reserved(result), "result not in heap"); return result; } if (GC_locker::is_active_and_needs_gc()) { if (is_tlab) { return NULL; // Caller will retry allocating individual object } if (!gch->is_maximal_no_gc()) { // Try and expand heap to satisfy request result = expand_heap_and_allocate(size, is_tlab); // result could be null if we are out of space if (result != NULL) { return result; } } if (gclocker_stalled_count > GCLockerRetryAllocationCount) { return NULL; // we didn't get to do a GC and we didn't get any memory } // If this thread is not in a jni critical section, we stall // the requestor until the critical section has cleared and // GC allowed. When the critical section clears, a GC is // initiated by the last thread exiting the critical section; so // we retry the allocation sequence from the beginning of the loop, // rather than causing more, now probably unnecessary, GC attempts. JavaThread* jthr = JavaThread::current(); if (!jthr->in_critical()) { MutexUnlocker mul(Heap_lock); // Wait for JNI critical section to be exited GC_locker::stall_until_clear(); gclocker_stalled_count += 1; continue; } else { if (CheckJNICalls) { fatal("Possible deadlock due to allocating while" " in jni critical section"); } return NULL; } } // Read the gc count while the heap lock is held. gc_count_before = Universe::heap()->total_collections(); } VM_GenCollectForAllocation op(size, is_tlab, gc_count_before); VMThread::execute(&op); if (op.prologue_succeeded()) { result = op.result(); if (op.gc_locked()) { assert(result == NULL, "must be NULL if gc_locked() is true"); continue; // retry and/or stall as necessary } // Allocation has failed and a collection // has been done. If the gc time limit was exceeded the // this time, return NULL so that an out-of-memory // will be thrown. Clear gc_overhead_limit_exceeded // so that the overhead exceeded does not persist. const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded(); const bool softrefs_clear = all_soft_refs_clear(); if (limit_exceeded && softrefs_clear) { *gc_overhead_limit_was_exceeded = true; size_policy()->set_gc_overhead_limit_exceeded(false); if (op.result() != NULL) { CollectedHeap::fill_with_object(op.result(), size); } return NULL; } assert(result == NULL || gch->is_in_reserved(result), "result not in heap"); return result; } // Give a warning if we seem to be looping forever. if ((QueuedAllocationWarningCount > 0) && (try_count % QueuedAllocationWarningCount == 0)) { warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t" " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : ""); } } } HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size, bool is_tlab) { GenCollectedHeap *gch = GenCollectedHeap::heap(); HeapWord* result = NULL; for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) { Generation *gen = gch->get_gen(i); if (gen->should_allocate(size, is_tlab)) { result = gen->expand_and_allocate(size, is_tlab); } } assert(result == NULL || gch->is_in_reserved(result), "result not in heap"); return result; } HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size, bool is_tlab) { GenCollectedHeap *gch = GenCollectedHeap::heap(); GCCauseSetter x(gch, GCCause::_allocation_failure); HeapWord* result = NULL; assert(size != 0, "Precondition violated"); if (GC_locker::is_active_and_needs_gc()) { // GC locker is active; instead of a collection we will attempt // to expand the heap, if there's room for expansion. if (!gch->is_maximal_no_gc()) { result = expand_heap_and_allocate(size, is_tlab); } return result; // could be null if we are out of space } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) { // Do an incremental collection. gch->do_collection(false /* full */, false /* clear_all_soft_refs */, size /* size */, is_tlab /* is_tlab */, number_of_generations() - 1 /* max_level */); } else { if (Verbose && PrintGCDetails) { gclog_or_tty->print(" :: Trying full because partial may fail :: "); } // Try a full collection; see delta for bug id 6266275 // for the original code and why this has been simplified // with from-space allocation criteria modified and // such allocation moved out of the safepoint path. gch->do_collection(true /* full */, false /* clear_all_soft_refs */, size /* size */, is_tlab /* is_tlab */, number_of_generations() - 1 /* max_level */); } result = gch->attempt_allocation(size, is_tlab, false /*first_only*/); if (result != NULL) { assert(gch->is_in_reserved(result), "result not in heap"); return result; } // OK, collection failed, try expansion. result = expand_heap_and_allocate(size, is_tlab); if (result != NULL) { return result; } // If we reach this point, we're really out of memory. Try every trick // we can to reclaim memory. Force collection of soft references. Force // a complete compaction of the heap. Any additional methods for finding // free memory should be here, especially if they are expensive. If this // attempt fails, an OOM exception will be thrown. { UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted gch->do_collection(true /* full */, true /* clear_all_soft_refs */, size /* size */, is_tlab /* is_tlab */, number_of_generations() - 1 /* max_level */); } result = gch->attempt_allocation(size, is_tlab, false /* first_only */); if (result != NULL) { assert(gch->is_in_reserved(result), "result not in heap"); return result; } assert(!should_clear_all_soft_refs(), "Flag should have been handled and cleared prior to this point"); // What else? We might try synchronous finalization later. If the total // space available is large enough for the allocation, then a more // complete compaction phase than we've tried so far might be // appropriate. return NULL; } MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation( ClassLoaderData* loader_data, size_t word_size, Metaspace::MetadataType mdtype) { uint loop_count = 0; uint gc_count = 0; uint full_gc_count = 0; assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock"); do { MetaWord* result = NULL; if (GC_locker::is_active_and_needs_gc()) { // If the GC_locker is active, just expand and allocate. // If that does not succeed, wait if this thread is not // in a critical section itself. result = loader_data->metaspace_non_null()->expand_and_allocate(word_size, mdtype); if (result != NULL) { return result; } JavaThread* jthr = JavaThread::current(); if (!jthr->in_critical()) { // Wait for JNI critical section to be exited GC_locker::stall_until_clear(); // The GC invoked by the last thread leaving the critical // section will be a young collection and a full collection // is (currently) needed for unloading classes so continue // to the next iteration to get a full GC. continue; } else { if (CheckJNICalls) { fatal("Possible deadlock due to allocating while" " in jni critical section"); } return NULL; } } { // Need lock to get self consistent gc_count's MutexLocker ml(Heap_lock); gc_count = Universe::heap()->total_collections(); full_gc_count = Universe::heap()->total_full_collections(); } // Generate a VM operation VM_CollectForMetadataAllocation op(loader_data, word_size, mdtype, gc_count, full_gc_count, GCCause::_metadata_GC_threshold); VMThread::execute(&op); // If GC was locked out, try again. Check // before checking success because the prologue // could have succeeded and the GC still have // been locked out. if (op.gc_locked()) { continue; } if (op.prologue_succeeded()) { return op.result(); } loop_count++; if ((QueuedAllocationWarningCount > 0) && (loop_count % QueuedAllocationWarningCount == 0)) { warning("satisfy_failed_metadata_allocation() retries %d times \n\t" " size=%d", loop_count, word_size); } } while (true); // Until a GC is done } // Return true if any of the following is true: // . the allocation won't fit into the current young gen heap // . gc locker is occupied (jni critical section) // . heap memory is tight -- the most recent previous collection // was a full collection because a partial collection (would // have) failed and is likely to fail again bool GenCollectorPolicy::should_try_older_generation_allocation( size_t word_size) const { GenCollectedHeap* gch = GenCollectedHeap::heap(); size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc(); return (word_size > heap_word_size(gen0_capacity)) || GC_locker::is_active_and_needs_gc() || gch->incremental_collection_failed(); } // // MarkSweepPolicy methods // MarkSweepPolicy::MarkSweepPolicy() { initialize_all(); } void MarkSweepPolicy::initialize_generations() { _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL); if (_generations == NULL) vm_exit_during_initialization("Unable to allocate gen spec"); if (UseParNewGC) { _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size); } else { _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size); } _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size); if (_generations[0] == NULL || _generations[1] == NULL) vm_exit_during_initialization("Unable to allocate gen spec"); } void MarkSweepPolicy::initialize_gc_policy_counters() { // initialize the policy counters - 2 collectors, 3 generations if (UseParNewGC) { _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3); } else { _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3); } }