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/*
* Copyright (c) 2001, 2023, 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
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*/
#include "precompiled.hpp"
#include "classfile/classLoaderDataGraph.hpp"
#include "classfile/metadataOnStackMark.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "code/icBuffer.hpp"
#include "compiler/oopMap.hpp"
#include "gc/g1/g1Allocator.inline.hpp"
#include "gc/g1/g1Arguments.hpp"
#include "gc/g1/g1BarrierSet.hpp"
#include "gc/g1/g1BatchedTask.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1CollectionSet.hpp"
#include "gc/g1/g1CollectionSetCandidates.hpp"
#include "gc/g1/g1CollectorState.hpp"
#include "gc/g1/g1ConcurrentRefine.hpp"
#include "gc/g1/g1ConcurrentRefineThread.hpp"
#include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
#include "gc/g1/g1DirtyCardQueue.hpp"
#include "gc/g1/g1EvacStats.inline.hpp"
#include "gc/g1/g1FullCollector.hpp"
#include "gc/g1/g1GCCounters.hpp"
#include "gc/g1/g1GCParPhaseTimesTracker.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1GCPauseType.hpp"
#include "gc/g1/g1HeapSizingPolicy.hpp"
#include "gc/g1/g1HeapTransition.hpp"
#include "gc/g1/g1HeapVerifier.hpp"
#include "gc/g1/g1InitLogger.hpp"
#include "gc/g1/g1MemoryPool.hpp"
#include "gc/g1/g1MonotonicArenaFreeMemoryTask.hpp"
#include "gc/g1/g1OopClosures.inline.hpp"
#include "gc/g1/g1ParallelCleaning.hpp"
#include "gc/g1/g1ParScanThreadState.inline.hpp"
#include "gc/g1/g1PeriodicGCTask.hpp"
#include "gc/g1/g1Policy.hpp"
#include "gc/g1/g1RedirtyCardsQueue.hpp"
#include "gc/g1/g1RegionToSpaceMapper.hpp"
#include "gc/g1/g1RemSet.hpp"
#include "gc/g1/g1RootClosures.hpp"
#include "gc/g1/g1RootProcessor.hpp"
#include "gc/g1/g1SATBMarkQueueSet.hpp"
#include "gc/g1/g1ServiceThread.hpp"
#include "gc/g1/g1ThreadLocalData.hpp"
#include "gc/g1/g1Trace.hpp"
#include "gc/g1/g1UncommitRegionTask.hpp"
#include "gc/g1/g1VMOperations.hpp"
#include "gc/g1/g1YoungCollector.hpp"
#include "gc/g1/g1YoungGCEvacFailureInjector.hpp"
#include "gc/g1/heapRegion.inline.hpp"
#include "gc/g1/heapRegionRemSet.inline.hpp"
#include "gc/g1/heapRegionSet.inline.hpp"
#include "gc/shared/classUnloadingContext.hpp"
#include "gc/shared/concurrentGCBreakpoints.hpp"
#include "gc/shared/gcBehaviours.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.inline.hpp"
#include "gc/shared/gcTimer.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "gc/shared/generationSpec.hpp"
#include "gc/shared/isGCActiveMark.hpp"
#include "gc/shared/locationPrinter.inline.hpp"
#include "gc/shared/oopStorageParState.hpp"
#include "gc/shared/preservedMarks.inline.hpp"
#include "gc/shared/referenceProcessor.inline.hpp"
#include "gc/shared/suspendibleThreadSet.hpp"
#include "gc/shared/taskqueue.inline.hpp"
#include "gc/shared/taskTerminator.hpp"
#include "gc/shared/tlab_globals.hpp"
#include "gc/shared/workerPolicy.hpp"
#include "gc/shared/weakProcessor.inline.hpp"
#include "logging/log.hpp"
#include "memory/allocation.hpp"
#include "memory/heapInspection.hpp"
#include "memory/iterator.hpp"
#include "memory/metaspaceUtils.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/compressedOops.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/init.hpp"
#include "runtime/java.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/threadSMR.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/align.hpp"
#include "utilities/autoRestore.hpp"
#include "utilities/bitMap.inline.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/stack.inline.hpp"
size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
// INVARIANTS/NOTES
//
// All allocation activity covered by the G1CollectedHeap interface is
// serialized by acquiring the HeapLock. This happens in mem_allocate
// and allocate_new_tlab, which are the "entry" points to the
// allocation code from the rest of the JVM. (Note that this does not
// apply to TLAB allocation, which is not part of this interface: it
// is done by clients of this interface.)
void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
}
void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
// The from card cache is not the memory that is actually committed. So we cannot
// take advantage of the zero_filled parameter.
reset_from_card_cache(start_idx, num_regions);
}
void G1CollectedHeap::run_batch_task(G1BatchedTask* cl) {
uint num_workers = MAX2(1u, MIN2(cl->num_workers_estimate(), workers()->active_workers()));
cl->set_max_workers(num_workers);
workers()->run_task(cl, num_workers);
}
uint G1CollectedHeap::get_chunks_per_region() {
uint log_region_size = HeapRegion::LogOfHRGrainBytes;
// Limit the expected input values to current known possible values of the
// (log) region size. Adjust as necessary after testing if changing the permissible
// values for region size.
assert(log_region_size >= 20 && log_region_size <= 29,
"expected value in [20,29], but got %u", log_region_size);
return 1u << (log_region_size / 2 - 4);
}
HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
MemRegion mr) {
return new HeapRegion(hrs_index, bot(), mr, &_card_set_config);
}
// Private methods.
HeapRegion* G1CollectedHeap::new_region(size_t word_size,
HeapRegionType type,
bool do_expand,
uint node_index) {
assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
"the only time we use this to allocate a humongous region is "
"when we are allocating a single humongous region");
HeapRegion* res = _hrm.allocate_free_region(type, node_index);
if (res == nullptr && do_expand) {
// Currently, only attempts to allocate GC alloc regions set
// do_expand to true. So, we should only reach here during a
// safepoint.
assert(SafepointSynchronize::is_at_safepoint(), "invariant");
log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
word_size * HeapWordSize);
assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
"This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
word_size * HeapWordSize);
if (expand_single_region(node_index)) {
// Given that expand_single_region() succeeded in expanding the heap, and we
// always expand the heap by an amount aligned to the heap
// region size, the free list should in theory not be empty.
// In either case allocate_free_region() will check for null.
res = _hrm.allocate_free_region(type, node_index);
}
}
return res;
}
void G1CollectedHeap::set_humongous_metadata(HeapRegion* first_hr,
uint num_regions,
size_t word_size,
bool update_remsets) {
// Calculate the new top of the humongous object.
HeapWord* obj_top = first_hr->bottom() + word_size;
// The word size sum of all the regions used
size_t word_size_sum = num_regions * HeapRegion::GrainWords;
assert(word_size <= word_size_sum, "sanity");
// How many words memory we "waste" which cannot hold a filler object.
size_t words_not_fillable = 0;
// Pad out the unused tail of the last region with filler
// objects, for improved usage accounting.
// How many words can we use for filler objects.
size_t words_fillable = word_size_sum - word_size;
if (words_fillable >= G1CollectedHeap::min_fill_size()) {
G1CollectedHeap::fill_with_objects(obj_top, words_fillable);
} else {
// We have space to fill, but we cannot fit an object there.
words_not_fillable = words_fillable;
words_fillable = 0;
}
// We will set up the first region as "starts humongous". This
// will also update the BOT covering all the regions to reflect
// that there is a single object that starts at the bottom of the
// first region.
first_hr->hr_clear(false /* clear_space */);
first_hr->set_starts_humongous(obj_top, words_fillable);
if (update_remsets) {
_policy->remset_tracker()->update_at_allocate(first_hr);
}
// Indices of first and last regions in the series.
uint first = first_hr->hrm_index();
uint last = first + num_regions - 1;
HeapRegion* hr = nullptr;
for (uint i = first + 1; i <= last; ++i) {
hr = region_at(i);
hr->hr_clear(false /* clear_space */);
hr->set_continues_humongous(first_hr);
if (update_remsets) {
_policy->remset_tracker()->update_at_allocate(hr);
}
}
// Up to this point no concurrent thread would have been able to
// do any scanning on any region in this series. All the top
// fields still point to bottom, so the intersection between
// [bottom,top] and [card_start,card_end] will be empty. Before we
// update the top fields, we'll do a storestore to make sure that
// no thread sees the update to top before the zeroing of the
// object header and the BOT initialization.
OrderAccess::storestore();
// Now, we will update the top fields of the "continues humongous"
// regions except the last one.
for (uint i = first; i < last; ++i) {
hr = region_at(i);
hr->set_top(hr->end());
}
hr = region_at(last);
// If we cannot fit a filler object, we must set top to the end
// of the humongous object, otherwise we cannot iterate the heap
// and the BOT will not be complete.
hr->set_top(hr->end() - words_not_fillable);
assert(hr->bottom() < obj_top && obj_top <= hr->end(),
"obj_top should be in last region");
assert(words_not_fillable == 0 ||
first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
"Miscalculation in humongous allocation");
}
HeapWord*
G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
uint num_regions,
size_t word_size) {
assert(first_hr != nullptr, "pre-condition");
assert(is_humongous(word_size), "word_size should be humongous");
assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
// Index of last region in the series.
uint first = first_hr->hrm_index();
uint last = first + num_regions - 1;
// We need to initialize the region(s) we just discovered. This is
// a bit tricky given that it can happen concurrently with
// refinement threads refining cards on these regions and
// potentially wanting to refine the BOT as they are scanning
// those cards (this can happen shortly after a cleanup; see CR
// 6991377). So we have to set up the region(s) carefully and in
// a specific order.
// The passed in hr will be the "starts humongous" region. The header
// of the new object will be placed at the bottom of this region.
HeapWord* new_obj = first_hr->bottom();
// First, we need to zero the header of the space that we will be
// allocating. When we update top further down, some refinement
// threads might try to scan the region. By zeroing the header we
// ensure that any thread that will try to scan the region will
// come across the zero klass word and bail out.
//
// NOTE: It would not have been correct to have used
// CollectedHeap::fill_with_object() and make the space look like
// an int array. The thread that is doing the allocation will
// later update the object header to a potentially different array
// type and, for a very short period of time, the klass and length
// fields will be inconsistent. This could cause a refinement
// thread to calculate the object size incorrectly.
Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
// Next, update the metadata for the regions.
set_humongous_metadata(first_hr, num_regions, word_size, true);
HeapRegion* last_hr = region_at(last);
size_t used = byte_size(first_hr->bottom(), last_hr->top());
increase_used(used);
for (uint i = first; i <= last; ++i) {
HeapRegion *hr = region_at(i);
_humongous_set.add(hr);
_hr_printer.alloc(hr);
}
return new_obj;
}
size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
}
// If could fit into free regions w/o expansion, try.
// Otherwise, if can expand, do so.
// Otherwise, if using ex regions might help, try with ex given back.
HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
_verifier->verify_region_sets_optional();
uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
// Policy: First try to allocate a humongous object in the free list.
HeapRegion* humongous_start = _hrm.allocate_humongous(obj_regions);
if (humongous_start == nullptr) {
// Policy: We could not find enough regions for the humongous object in the
// free list. Look through the heap to find a mix of free and uncommitted regions.
// If so, expand the heap and allocate the humongous object.
humongous_start = _hrm.expand_and_allocate_humongous(obj_regions);
if (humongous_start != nullptr) {
// We managed to find a region by expanding the heap.
log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
word_size * HeapWordSize);
policy()->record_new_heap_size(num_regions());
} else {
// Policy: Potentially trigger a defragmentation GC.
}
}
HeapWord* result = nullptr;
if (humongous_start != nullptr) {
result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
assert(result != nullptr, "it should always return a valid result");
// A successful humongous object allocation changes the used space
// information of the old generation so we need to recalculate the
// sizes and update the jstat counters here.
monitoring_support()->update_sizes();
}
_verifier->verify_region_sets_optional();
return result;
}
HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
size_t requested_size,
size_t* actual_size) {
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
return attempt_allocation(min_size, requested_size, actual_size);
}
HeapWord*
G1CollectedHeap::mem_allocate(size_t word_size,
bool* gc_overhead_limit_was_exceeded) {
assert_heap_not_locked_and_not_at_safepoint();
if (is_humongous(word_size)) {
return attempt_allocation_humongous(word_size);
}
size_t dummy = 0;
return attempt_allocation(word_size, word_size, &dummy);
}
HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
ResourceMark rm; // For retrieving the thread names in log messages.
// Make sure you read the note in attempt_allocation_humongous().
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
"be called for humongous allocation requests");
// We should only get here after the first-level allocation attempt
// (attempt_allocation()) failed to allocate.
// We will loop until a) we manage to successfully perform the
// allocation or b) we successfully schedule a collection which
// fails to perform the allocation. b) is the only case when we'll
// return null.
HeapWord* result = nullptr;
for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
bool should_try_gc;
uint gc_count_before;
{
MutexLocker x(Heap_lock);
// Now that we have the lock, we first retry the allocation in case another
// thread changed the region while we were waiting to acquire the lock.
result = _allocator->attempt_allocation_locked(word_size);
if (result != nullptr) {
return result;
}
// If the GCLocker is active and we are bound for a GC, try expanding young gen.
// This is different to when only GCLocker::needs_gc() is set: try to avoid
// waiting because the GCLocker is active to not wait too long.
if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
// No need for an ergo message here, can_expand_young_list() does this when
// it returns true.
result = _allocator->attempt_allocation_force(word_size);
if (result != nullptr) {
return result;
}
}
// Only try a GC if the GCLocker does not signal the need for a GC. Wait until
// the GCLocker initiated GC has been performed and then retry. This includes
// the case when the GC Locker is not active but has not been performed.
should_try_gc = !GCLocker::needs_gc();
// Read the GC count while still holding the Heap_lock.
gc_count_before = total_collections();
}
if (should_try_gc) {
bool succeeded;
result = do_collection_pause(word_size, gc_count_before, &succeeded, GCCause::_g1_inc_collection_pause);
if (result != nullptr) {
assert(succeeded, "only way to get back a non-null result");
log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
Thread::current()->name(), p2i(result));
return result;
}
if (succeeded) {
// We successfully scheduled a collection which failed to allocate. No
// point in trying to allocate further. We'll just return null.
log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
SIZE_FORMAT " words", Thread::current()->name(), word_size);
return nullptr;
}
log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
Thread::current()->name(), word_size);
} else {
// Failed to schedule a collection.
if (gclocker_retry_count > GCLockerRetryAllocationCount) {
log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
SIZE_FORMAT " words", Thread::current()->name(), word_size);
return nullptr;
}
log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
// The GCLocker is either active or the GCLocker initiated
// GC has not yet been performed. Stall until it is and
// then retry the allocation.
GCLocker::stall_until_clear();
gclocker_retry_count += 1;
}
// We can reach here if we were unsuccessful in scheduling a
// collection (because another thread beat us to it) or if we were
// stalled due to the GC locker. In either can we should retry the
// allocation attempt in case another thread successfully
// performed a collection and reclaimed enough space. We do the
// first attempt (without holding the Heap_lock) here and the
// follow-on attempt will be at the start of the next loop
// iteration (after taking the Heap_lock).
size_t dummy = 0;
result = _allocator->attempt_allocation(word_size, word_size, &dummy);
if (result != nullptr) {
return result;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
Thread::current()->name(), try_count, word_size);
}
}
ShouldNotReachHere();
return nullptr;
}
bool G1CollectedHeap::check_archive_addresses(MemRegion range) {
return _hrm.reserved().contains(range);
}
template <typename Func>
void G1CollectedHeap::iterate_regions_in_range(MemRegion range, const Func& func) {
// Mark each G1 region touched by the range as old, add it to
// the old set, and set top.
HeapRegion* curr_region = _hrm.addr_to_region(range.start());
HeapRegion* end_region = _hrm.addr_to_region(range.last());
while (curr_region != nullptr) {
bool is_last = curr_region == end_region;
HeapRegion* next_region = is_last ? nullptr : _hrm.next_region_in_heap(curr_region);
func(curr_region, is_last);
curr_region = next_region;
}
}
bool G1CollectedHeap::alloc_archive_regions(MemRegion range) {
assert(!is_init_completed(), "Expect to be called at JVM init time");
MutexLocker x(Heap_lock);
MemRegion reserved = _hrm.reserved();
// Temporarily disable pretouching of heap pages. This interface is used
// when mmap'ing archived heap data in, so pre-touching is wasted.
FlagSetting fs(AlwaysPreTouch, false);
// For the specified MemRegion range, allocate the corresponding G1
// region(s) and mark them as old region(s).
HeapWord* start_address = range.start();
size_t word_size = range.word_size();
HeapWord* last_address = range.last();
size_t commits = 0;
guarantee(reserved.contains(start_address) && reserved.contains(last_address),
"MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
p2i(start_address), p2i(last_address));
// Perform the actual region allocation, exiting if it fails.
// Then note how much new space we have allocated.
if (!_hrm.allocate_containing_regions(range, &commits, workers())) {
return false;
}
increase_used(word_size * HeapWordSize);
if (commits != 0) {
log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
HeapRegion::GrainWords * HeapWordSize * commits);
}
// Mark each G1 region touched by the range as old, add it to
// the old set, and set top.
auto set_region_to_old = [&] (HeapRegion* r, bool is_last) {
assert(r->is_empty(), "Region already in use (%u)", r->hrm_index());
HeapWord* top = is_last ? last_address + 1 : r->end();
r->set_top(top);
r->set_old();
_hr_printer.alloc(r);
_old_set.add(r);
};
iterate_regions_in_range(range, set_region_to_old);
return true;
}
void G1CollectedHeap::populate_archive_regions_bot_part(MemRegion range) {
assert(!is_init_completed(), "Expect to be called at JVM init time");
iterate_regions_in_range(range,
[&] (HeapRegion* r, bool is_last) {
r->update_bot();
});
}
void G1CollectedHeap::dealloc_archive_regions(MemRegion range) {
assert(!is_init_completed(), "Expect to be called at JVM init time");
MemRegion reserved = _hrm.reserved();
size_t size_used = 0;
uint shrink_count = 0;
// Free the G1 regions that are within the specified range.
MutexLocker x(Heap_lock);
HeapWord* start_address = range.start();
HeapWord* last_address = range.last();
assert(reserved.contains(start_address) && reserved.contains(last_address),
"MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
p2i(start_address), p2i(last_address));
size_used += range.byte_size();
// Free, empty and uncommit regions with CDS archive content.
auto dealloc_archive_region = [&] (HeapRegion* r, bool is_last) {
guarantee(r->is_old(), "Expected old region at index %u", r->hrm_index());
_old_set.remove(r);
r->set_free();
r->set_top(r->bottom());
_hrm.shrink_at(r->hrm_index(), 1);
shrink_count++;
};
iterate_regions_in_range(range, dealloc_archive_region);
if (shrink_count != 0) {
log_debug(gc, ergo, heap)("Attempt heap shrinking (CDS archive regions). Total size: " SIZE_FORMAT "B",
HeapRegion::GrainWords * HeapWordSize * shrink_count);
// Explicit uncommit.
uncommit_regions(shrink_count);
}
decrease_used(size_used);
}
inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
size_t desired_word_size,
size_t* actual_word_size) {
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
"be called for humongous allocation requests");
HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
if (result == nullptr) {
*actual_word_size = desired_word_size;
result = attempt_allocation_slow(desired_word_size);
}
assert_heap_not_locked();
if (result != nullptr) {
assert(*actual_word_size != 0, "Actual size must have been set here");
dirty_young_block(result, *actual_word_size);
} else {
*actual_word_size = 0;
}
return result;
}
HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
ResourceMark rm; // For retrieving the thread names in log messages.
// The structure of this method has a lot of similarities to
// attempt_allocation_slow(). The reason these two were not merged
// into a single one is that such a method would require several "if
// allocation is not humongous do this, otherwise do that"
// conditional paths which would obscure its flow. In fact, an early
// version of this code did use a unified method which was harder to
// follow and, as a result, it had subtle bugs that were hard to
// track down. So keeping these two methods separate allows each to
// be more readable. It will be good to keep these two in sync as
// much as possible.
assert_heap_not_locked_and_not_at_safepoint();
assert(is_humongous(word_size), "attempt_allocation_humongous() "
"should only be called for humongous allocations");
// Humongous objects can exhaust the heap quickly, so we should check if we
// need to start a marking cycle at each humongous object allocation. We do
// the check before we do the actual allocation. The reason for doing it
// before the allocation is that we avoid having to keep track of the newly
// allocated memory while we do a GC.
if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
word_size)) {
collect(GCCause::_g1_humongous_allocation);
}
// We will loop until a) we manage to successfully perform the
// allocation or b) we successfully schedule a collection which
// fails to perform the allocation. b) is the only case when we'll
// return null.
HeapWord* result = nullptr;
for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
bool should_try_gc;
uint gc_count_before;
{
MutexLocker x(Heap_lock);
size_t size_in_regions = humongous_obj_size_in_regions(word_size);
// Given that humongous objects are not allocated in young
// regions, we'll first try to do the allocation without doing a
// collection hoping that there's enough space in the heap.
result = humongous_obj_allocate(word_size);
if (result != nullptr) {
policy()->old_gen_alloc_tracker()->
add_allocated_humongous_bytes_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
return result;
}
// Only try a GC if the GCLocker does not signal the need for a GC. Wait until
// the GCLocker initiated GC has been performed and then retry. This includes
// the case when the GC Locker is not active but has not been performed.
should_try_gc = !GCLocker::needs_gc();
// Read the GC count while still holding the Heap_lock.
gc_count_before = total_collections();
}
if (should_try_gc) {
bool succeeded;
result = do_collection_pause(word_size, gc_count_before, &succeeded, GCCause::_g1_humongous_allocation);
if (result != nullptr) {
assert(succeeded, "only way to get back a non-null result");
log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
Thread::current()->name(), p2i(result));
size_t size_in_regions = humongous_obj_size_in_regions(word_size);
policy()->old_gen_alloc_tracker()->
record_collection_pause_humongous_allocation(size_in_regions * HeapRegion::GrainBytes);
return result;
}
if (succeeded) {
// We successfully scheduled a collection which failed to allocate. No
// point in trying to allocate further. We'll just return null.
log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
SIZE_FORMAT " words", Thread::current()->name(), word_size);
return nullptr;
}
log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
Thread::current()->name(), word_size);
} else {
// Failed to schedule a collection.
if (gclocker_retry_count > GCLockerRetryAllocationCount) {
log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
SIZE_FORMAT " words", Thread::current()->name(), word_size);
return nullptr;
}
log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
// The GCLocker is either active or the GCLocker initiated
// GC has not yet been performed. Stall until it is and
// then retry the allocation.
GCLocker::stall_until_clear();
gclocker_retry_count += 1;
}
// We can reach here if we were unsuccessful in scheduling a
// collection (because another thread beat us to it) or if we were
// stalled due to the GC locker. In either can we should retry the
// allocation attempt in case another thread successfully
// performed a collection and reclaimed enough space.
// Humongous object allocation always needs a lock, so we wait for the retry
// in the next iteration of the loop, unlike for the regular iteration case.
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
Thread::current()->name(), try_count, word_size);
}
}
ShouldNotReachHere();
return nullptr;
}
HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
bool expect_null_mutator_alloc_region) {
assert_at_safepoint_on_vm_thread();
assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
"the current alloc region was unexpectedly found to be non-null");
if (!is_humongous(word_size)) {
return _allocator->attempt_allocation_locked(word_size);
} else {
HeapWord* result = humongous_obj_allocate(word_size);
if (result != nullptr && policy()->need_to_start_conc_mark("STW humongous allocation")) {
collector_state()->set_initiate_conc_mark_if_possible(true);
}
return result;
}
ShouldNotReachHere();
}
class PostCompactionPrinterClosure: public HeapRegionClosure {
private:
G1HRPrinter* _hr_printer;
public:
bool do_heap_region(HeapRegion* hr) {
assert(!hr->is_young(), "not expecting to find young regions");
_hr_printer->post_compaction(hr);
return false;
}
PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
: _hr_printer(hr_printer) { }
};
void G1CollectedHeap::print_heap_after_full_collection() {
// Post collection region logging.
// We should do this after we potentially resize the heap so
// that all the COMMIT / UNCOMMIT events are generated before
// the compaction events.
if (_hr_printer.is_active()) {
PostCompactionPrinterClosure cl(hr_printer());
heap_region_iterate(&cl);
}
}
bool G1CollectedHeap::abort_concurrent_cycle() {
// Disable discovery and empty the discovered lists
// for the CM ref processor.
_ref_processor_cm->disable_discovery();
_ref_processor_cm->abandon_partial_discovery();
_ref_processor_cm->verify_no_references_recorded();
// Abandon current iterations of concurrent marking and concurrent
// refinement, if any are in progress.
return concurrent_mark()->concurrent_cycle_abort();
}
void G1CollectedHeap::prepare_heap_for_full_collection() {
// Make sure we'll choose a new allocation region afterwards.
_allocator->release_mutator_alloc_regions();
_allocator->abandon_gc_alloc_regions();
// We may have added regions to the current incremental collection
// set between the last GC or pause and now. We need to clear the
// incremental collection set and then start rebuilding it afresh
// after this full GC.
abandon_collection_set(collection_set());
_hrm.remove_all_free_regions();
}
void G1CollectedHeap::verify_before_full_collection() {
assert_used_and_recalculate_used_equal(this);
if (!VerifyBeforeGC) {
return;
}
if (!G1HeapVerifier::should_verify(G1HeapVerifier::G1VerifyFull)) {
return;
}
_verifier->verify_region_sets_optional();
_verifier->verify_before_gc();
_verifier->verify_bitmap_clear(true /* above_tams_only */);
}
void G1CollectedHeap::prepare_for_mutator_after_full_collection() {
// Prepare heap for normal collections.
assert(num_free_regions() == 0, "we should not have added any free regions");
rebuild_region_sets(false /* free_list_only */);
abort_refinement();
resize_heap_if_necessary();
uncommit_regions_if_necessary();
// Rebuild the code root lists for each region
rebuild_code_roots();
start_new_collection_set();
_allocator->init_mutator_alloc_regions();
// Post collection state updates.
MetaspaceGC::compute_new_size();
}
void G1CollectedHeap::abort_refinement() {
// Discard all remembered set updates and reset refinement statistics.
G1BarrierSet::dirty_card_queue_set().abandon_logs_and_stats();
assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
"DCQS should be empty");
concurrent_refine()->get_and_reset_refinement_stats();
}
void G1CollectedHeap::verify_after_full_collection() {
if (!VerifyAfterGC) {
return;
}
if (!G1HeapVerifier::should_verify(G1HeapVerifier::G1VerifyFull)) {
return;
}
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
_verifier->verify_after_gc();
_verifier->verify_bitmap_clear(false /* above_tams_only */);
// At this point there should be no regions in the
// entire heap tagged as young.
assert(check_young_list_empty(), "young list should be empty at this point");
// Note: since we've just done a full GC, concurrent
// marking is no longer active. Therefore we need not
// re-enable reference discovery for the CM ref processor.
// That will be done at the start of the next marking cycle.
// We also know that the STW processor should no longer
// discover any new references.
assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
_ref_processor_stw->verify_no_references_recorded();
_ref_processor_cm->verify_no_references_recorded();
}
bool G1CollectedHeap::do_full_collection(bool clear_all_soft_refs,
bool do_maximal_compaction) {
assert_at_safepoint_on_vm_thread();
if (GCLocker::check_active_before_gc()) {
// Full GC was not completed.
return false;
}
const bool do_clear_all_soft_refs = clear_all_soft_refs ||
soft_ref_policy()->should_clear_all_soft_refs();
G1FullGCMark gc_mark;
GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause(), true);
G1FullCollector collector(this, do_clear_all_soft_refs, do_maximal_compaction, gc_mark.tracer());
collector.prepare_collection();
collector.collect();
collector.complete_collection();
// Full collection was successfully completed.
return true;
}
void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
// Currently, there is no facility in the do_full_collection(bool) API to notify
// the caller that the collection did not succeed (e.g., because it was locked
// out by the GC locker). So, right now, we'll ignore the return value.
do_full_collection(clear_all_soft_refs,
false /* do_maximal_compaction */);
}
bool G1CollectedHeap::upgrade_to_full_collection() {
GCCauseSetter compaction(this, GCCause::_g1_compaction_pause);
log_info(gc, ergo)("Attempting full compaction clearing soft references");
bool success = do_full_collection(true /* clear_all_soft_refs */,
false /* do_maximal_compaction */);
// do_full_collection only fails if blocked by GC locker and that can't
// be the case here since we only call this when already completed one gc.
assert(success, "invariant");
return success;
}
void G1CollectedHeap::resize_heap_if_necessary() {
assert_at_safepoint_on_vm_thread();
bool should_expand;
size_t resize_amount = _heap_sizing_policy->full_collection_resize_amount(should_expand);
if (resize_amount == 0) {
return;
} else if (should_expand) {
expand(resize_amount, _workers);
} else {
shrink(resize_amount);
}
}
HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
bool do_gc,
bool maximal_compaction,
bool expect_null_mutator_alloc_region,
bool* gc_succeeded) {
*gc_succeeded = true;
// Let's attempt the allocation first.
HeapWord* result =
attempt_allocation_at_safepoint(word_size,
expect_null_mutator_alloc_region);
if (result != nullptr) {
return result;
}
// In a G1 heap, we're supposed to keep allocation from failing by
// incremental pauses. Therefore, at least for now, we'll favor
// expansion over collection. (This might change in the future if we can
// do something smarter than full collection to satisfy a failed alloc.)
result = expand_and_allocate(word_size);
if (result != nullptr) {
return result;
}
if (do_gc) {
GCCauseSetter compaction(this, GCCause::_g1_compaction_pause);
// Expansion didn't work, we'll try to do a Full GC.
// If maximal_compaction is set we clear all soft references and don't
// allow any dead wood to be left on the heap.
if (maximal_compaction) {
log_info(gc, ergo)("Attempting maximal full compaction clearing soft references");
} else {
log_info(gc, ergo)("Attempting full compaction");
}
*gc_succeeded = do_full_collection(maximal_compaction /* clear_all_soft_refs */ ,
maximal_compaction /* do_maximal_compaction */);
}
return nullptr;
}
HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
bool* succeeded) {
assert_at_safepoint_on_vm_thread();
// Attempts to allocate followed by Full GC.
HeapWord* result =
satisfy_failed_allocation_helper(word_size,
true, /* do_gc */
false, /* maximum_collection */
false, /* expect_null_mutator_alloc_region */
succeeded);
if (result != nullptr || !*succeeded) {
return result;
}
// Attempts to allocate followed by Full GC that will collect all soft references.
result = satisfy_failed_allocation_helper(word_size,
true, /* do_gc */
true, /* maximum_collection */
true, /* expect_null_mutator_alloc_region */
succeeded);
if (result != nullptr || !*succeeded) {
return result;
}
// Attempts to allocate, no GC
result = satisfy_failed_allocation_helper(word_size,
false, /* do_gc */
false, /* maximum_collection */
true, /* expect_null_mutator_alloc_region */
succeeded);
if (result != nullptr) {
return result;
}
assert(!soft_ref_policy()->should_clear_all_soft_refs(),
"Flag should have been handled and cleared prior to this point");
// What else? We might try synchronous finalization later. If the total
// space available is large enough for the allocation, then a more
// complete compaction phase than we've tried so far might be
// appropriate.
return nullptr;
}
// Attempting to expand the heap sufficiently
// to support an allocation of the given "word_size". If
// successful, perform the allocation and return the address of the
// allocated block, or else null.
HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
assert_at_safepoint_on_vm_thread();
_verifier->verify_region_sets_optional();
size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
word_size * HeapWordSize);
if (expand(expand_bytes, _workers)) {
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
return attempt_allocation_at_safepoint(word_size,
false /* expect_null_mutator_alloc_region */);
}
return nullptr;
}
bool G1CollectedHeap::expand(size_t expand_bytes, WorkerThreads* pretouch_workers, double* expand_time_ms) {
size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
aligned_expand_bytes = align_up(aligned_expand_bytes,
HeapRegion::GrainBytes);
log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
expand_bytes, aligned_expand_bytes);
if (is_maximal_no_gc()) {
log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
return false;
}
double expand_heap_start_time_sec = os::elapsedTime();
uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
assert(regions_to_expand > 0, "Must expand by at least one region");
uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
if (expand_time_ms != nullptr) {
*expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
}
assert(expanded_by > 0, "must have failed during commit.");
size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
policy()->record_new_heap_size(num_regions());
return true;
}
bool G1CollectedHeap::expand_single_region(uint node_index) {
uint expanded_by = _hrm.expand_on_preferred_node(node_index);
if (expanded_by == 0) {
assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm.available());
log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
return false;
}
policy()->record_new_heap_size(num_regions());
return true;
}
void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
size_t aligned_shrink_bytes =
ReservedSpace::page_align_size_down(shrink_bytes);
aligned_shrink_bytes = align_down(aligned_shrink_bytes,
HeapRegion::GrainBytes);
uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B actual amount shrunk: " SIZE_FORMAT "B",
shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
if (num_regions_removed > 0) {
log_debug(gc, heap)("Uncommittable regions after shrink: %u", num_regions_removed);
policy()->record_new_heap_size(num_regions());
} else {
log_debug(gc, ergo, heap)("Did not shrink the heap (heap shrinking operation failed)");
}
}
void G1CollectedHeap::shrink(size_t shrink_bytes) {
_verifier->verify_region_sets_optional();
// We should only reach here at the end of a Full GC or during Remark which
// means we should not not be holding to any GC alloc regions. The method
// below will make sure of that and do any remaining clean up.
_allocator->abandon_gc_alloc_regions();
// Instead of tearing down / rebuilding the free lists here, we
// could instead use the remove_all_pending() method on free_list to
// remove only the ones that we need to remove.
_hrm.remove_all_free_regions();
shrink_helper(shrink_bytes);
rebuild_region_sets(true /* free_list_only */);
_hrm.verify_optional();
_verifier->verify_region_sets_optional();
}
class OldRegionSetChecker : public HeapRegionSetChecker {
public:
void check_mt_safety() {
// Master Old Set MT safety protocol:
// (a) If we're at a safepoint, operations on the master old set
// should be invoked:
// - by the VM thread (which will serialize them), or
// - by the GC workers while holding the FreeList_lock, if we're
// at a safepoint for an evacuation pause (this lock is taken
// anyway when an GC alloc region is retired so that a new one
// is allocated from the free list), or
// - by the GC workers while holding the OldSets_lock, if we're at a
// safepoint for a cleanup pause.
// (b) If we're not at a safepoint, operations on the master old set
// should be invoked while holding the Heap_lock.
if (SafepointSynchronize::is_at_safepoint()) {
guarantee(Thread::current()->is_VM_thread() ||
FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
"master old set MT safety protocol at a safepoint");
} else {
guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
}
}
bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
const char* get_description() { return "Old Regions"; }
};
class HumongousRegionSetChecker : public HeapRegionSetChecker {
public:
void check_mt_safety() {
// Humongous Set MT safety protocol:
// (a) If we're at a safepoint, operations on the master humongous
// set should be invoked by either the VM thread (which will
// serialize them) or by the GC workers while holding the
// OldSets_lock.
// (b) If we're not at a safepoint, operations on the master
// humongous set should be invoked while holding the Heap_lock.
if (SafepointSynchronize::is_at_safepoint()) {
guarantee(Thread::current()->is_VM_thread() ||
OldSets_lock->owned_by_self(),
"master humongous set MT safety protocol at a safepoint");
} else {
guarantee(Heap_lock->owned_by_self(),
"master humongous set MT safety protocol outside a safepoint");
}
}
bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
const char* get_description() { return "Humongous Regions"; }
};
G1CollectedHeap::G1CollectedHeap() :
CollectedHeap(),
_service_thread(nullptr),
_periodic_gc_task(nullptr),
_free_arena_memory_task(nullptr),
_workers(nullptr),
_card_table(nullptr),
_collection_pause_end(Ticks::now()),
_soft_ref_policy(),
_old_set("Old Region Set", new OldRegionSetChecker()),
_humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
_bot(nullptr),
_listener(),
_numa(G1NUMA::create()),
_hrm(),
_allocator(nullptr),
_evac_failure_injector(),
_verifier(nullptr),
_summary_bytes_used(0),
_bytes_used_during_gc(0),
_survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
_old_evac_stats("Old", OldPLABSize, PLABWeight),
_monitoring_support(nullptr),
_num_humongous_objects(0),
_num_humongous_reclaim_candidates(0),
_hr_printer(),
_collector_state(),
_old_marking_cycles_started(0),
_old_marking_cycles_completed(0),
_eden(),
_survivor(),
_gc_timer_stw(new STWGCTimer()),
_gc_tracer_stw(new G1NewTracer()),
_policy(new G1Policy(_gc_timer_stw)),
_heap_sizing_policy(nullptr),
_collection_set(this, _policy),
_rem_set(nullptr),
_card_set_config(),
_card_set_freelist_pool(G1CardSetConfiguration::num_mem_object_types()),
_cm(nullptr),
_cm_thread(nullptr),
_cr(nullptr),
_task_queues(nullptr),
_ref_processor_stw(nullptr),
_is_alive_closure_stw(this),
_is_subject_to_discovery_stw(this),
_ref_processor_cm(nullptr),
_is_alive_closure_cm(this),
_is_subject_to_discovery_cm(this),
_region_attr() {
_verifier = new G1HeapVerifier(this);
_allocator = new G1Allocator(this);
_heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
_humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
// Override the default _filler_array_max_size so that no humongous filler
// objects are created.
_filler_array_max_size = _humongous_object_threshold_in_words;
// Override the default _stack_chunk_max_size so that no humongous stack chunks are created
_stack_chunk_max_size = _humongous_object_threshold_in_words;
uint n_queues = ParallelGCThreads;
_task_queues = new G1ScannerTasksQueueSet(n_queues);
for (uint i = 0; i < n_queues; i++) {
G1ScannerTasksQueue* q = new G1ScannerTasksQueue();
_task_queues->register_queue(i, q);
}
_gc_tracer_stw->initialize();
guarantee(_task_queues != nullptr, "task_queues allocation failure.");
}
G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
size_t size,
size_t translation_factor) {
size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
// Allocate a new reserved space, preferring to use large pages.
ReservedSpace rs(size, preferred_page_size);
size_t page_size = rs.page_size();
G1RegionToSpaceMapper* result =
G1RegionToSpaceMapper::create_mapper(rs,
size,
page_size,
HeapRegion::GrainBytes,
translation_factor,
mtGC);
os::trace_page_sizes_for_requested_size(description,
size,
page_size,
preferred_page_size,
rs.base(),
rs.size());
return result;
}
jint G1CollectedHeap::initialize_concurrent_refinement() {
jint ecode = JNI_OK;
_cr = G1ConcurrentRefine::create(policy(), &ecode);
return ecode;
}
jint G1CollectedHeap::initialize_service_thread() {
_service_thread = new G1ServiceThread();
if (_service_thread->osthread() == nullptr) {
vm_shutdown_during_initialization("Could not create G1ServiceThread");
return JNI_ENOMEM;
}
return JNI_OK;
}
jint G1CollectedHeap::initialize() {
// Necessary to satisfy locking discipline assertions.
MutexLocker x(Heap_lock);
// While there are no constraints in the GC code that HeapWordSize
// be any particular value, there are multiple other areas in the
// system which believe this to be true (e.g. oop->object_size in some
// cases incorrectly returns the size in wordSize units rather than
// HeapWordSize).
guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
size_t init_byte_size = InitialHeapSize;
size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
// Ensure that the sizes are properly aligned.
Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
// Reserve the maximum.
// When compressed oops are enabled, the preferred heap base
// is calculated by subtracting the requested size from the
// 32Gb boundary and using the result as the base address for
// heap reservation. If the requested size is not aligned to
// HeapRegion::GrainBytes (i.e. the alignment that is passed
// into the ReservedHeapSpace constructor) then the actual
// base of the reserved heap may end up differing from the
// address that was requested (i.e. the preferred heap base).
// If this happens then we could end up using a non-optimal
// compressed oops mode.
ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
HeapAlignment);
initialize_reserved_region(heap_rs);
// Create the barrier set for the entire reserved region.
G1CardTable* ct = new G1CardTable(heap_rs.region());
G1BarrierSet* bs = new G1BarrierSet(ct);
bs->initialize();
assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
BarrierSet::set_barrier_set(bs);
_card_table = ct;
{
G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
}
// Create space mappers.
size_t page_size = heap_rs.page_size();
G1RegionToSpaceMapper* heap_storage =
G1RegionToSpaceMapper::create_mapper(heap_rs,
heap_rs.size(),
page_size,
HeapRegion::GrainBytes,
1,
mtJavaHeap);
if(heap_storage == nullptr) {
vm_shutdown_during_initialization("Could not initialize G1 heap");
return JNI_ERR;
}
os::trace_page_sizes("Heap",
MinHeapSize,
reserved_byte_size,
page_size,
heap_rs.base(),
heap_rs.size());
heap_storage->set_mapping_changed_listener(&_listener);
// Create storage for the BOT, card table and the bitmap.
G1RegionToSpaceMapper* bot_storage =
create_aux_memory_mapper("Block Offset Table",
G1BlockOffsetTable::compute_size(heap_rs.size() / HeapWordSize),
G1BlockOffsetTable::heap_map_factor());
G1RegionToSpaceMapper* cardtable_storage =
create_aux_memory_mapper("Card Table",
G1CardTable::compute_size(heap_rs.size() / HeapWordSize),
G1CardTable::heap_map_factor());
size_t bitmap_size = G1CMBitMap::compute_size(heap_rs.size());
G1RegionToSpaceMapper* bitmap_storage =
create_aux_memory_mapper("Mark Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
_hrm.initialize(heap_storage, bitmap_storage, bot_storage, cardtable_storage);
_card_table->initialize(cardtable_storage);
// 6843694 - ensure that the maximum region index can fit
// in the remembered set structures.
const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
guarantee((max_reserved_regions() - 1) <= max_region_idx, "too many regions");
// The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
// start within the first card.
guarantee((uintptr_t)(heap_rs.base()) >= G1CardTable::card_size(), "Java heap must not start within the first card.");
G1FromCardCache::initialize(max_reserved_regions());
// Also create a G1 rem set.
_rem_set = new G1RemSet(this, _card_table);
_rem_set->initialize(max_reserved_regions());
size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
"too many cards per region");
HeapRegionRemSet::initialize(_reserved);
FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
_bot = new G1BlockOffsetTable(reserved(), bot_storage);
{
size_t granularity = HeapRegion::GrainBytes;
_region_attr.initialize(reserved(), granularity);
}
_workers = new WorkerThreads("GC Thread", ParallelGCThreads);
if (_workers == nullptr) {
return JNI_ENOMEM;
}
_workers->initialize_workers();
_numa->set_region_info(HeapRegion::GrainBytes, page_size);
// Create the G1ConcurrentMark data structure and thread.
// (Must do this late, so that "max_[reserved_]regions" is defined.)
_cm = new G1ConcurrentMark(this, bitmap_storage);
_cm_thread = _cm->cm_thread();
// Now expand into the initial heap size.
if (!expand(init_byte_size, _workers)) {
vm_shutdown_during_initialization("Failed to allocate initial heap.");
return JNI_ENOMEM;
}
// Perform any initialization actions delegated to the policy.
policy()->init(this, &_collection_set);
jint ecode = initialize_concurrent_refinement();
if (ecode != JNI_OK) {
return ecode;
}
ecode = initialize_service_thread();
if (ecode != JNI_OK) {
return ecode;
}
// Create and schedule the periodic gc task on the service thread.
_periodic_gc_task = new G1PeriodicGCTask("Periodic GC Task");
_service_thread->register_task(_periodic_gc_task);
_free_arena_memory_task = new G1MonotonicArenaFreeMemoryTask("Card Set Free Memory Task");
_service_thread->register_task(_free_arena_memory_task);
// Here we allocate the dummy HeapRegion that is required by the
// G1AllocRegion class.
HeapRegion* dummy_region = _hrm.get_dummy_region();
// We'll re-use the same region whether the alloc region will
// require BOT updates or not and, if it doesn't, then a non-young
// region will complain that it cannot support allocations without
// BOT updates. So we'll tag the dummy region as eden to avoid that.
dummy_region->set_eden();
// Make sure it's full.
dummy_region->set_top(dummy_region->end());
G1AllocRegion::setup(this, dummy_region);
_allocator->init_mutator_alloc_regions();
// Do create of the monitoring and management support so that
// values in the heap have been properly initialized.
_monitoring_support = new G1MonitoringSupport(this);
_collection_set.initialize(max_reserved_regions());
evac_failure_injector()->reset();
G1InitLogger::print();
return JNI_OK;
}
bool G1CollectedHeap::concurrent_mark_is_terminating() const {
return _cm_thread->should_terminate();
}
void G1CollectedHeap::stop() {
// Stop all concurrent threads. We do this to make sure these threads
// do not continue to execute and access resources (e.g. logging)
// that are destroyed during shutdown.
_cr->stop();
_service_thread->stop();
_cm_thread->stop();
}
void G1CollectedHeap::safepoint_synchronize_begin() {
SuspendibleThreadSet::synchronize();
}
void G1CollectedHeap::safepoint_synchronize_end() {
SuspendibleThreadSet::desynchronize();
}
void G1CollectedHeap::post_initialize() {
CollectedHeap::post_initialize();
ref_processing_init();
}
void G1CollectedHeap::ref_processing_init() {
// Reference processing in G1 currently works as follows:
//
// * There are two reference processor instances. One is
// used to record and process discovered references
// during concurrent marking; the other is used to
// record and process references during STW pauses
// (both full and incremental).
// * Both ref processors need to 'span' the entire heap as
// the regions in the collection set may be dotted around.
//
// * For the concurrent marking ref processor:
// * Reference discovery is enabled at concurrent start.
// * Reference discovery is disabled and the discovered
// references processed etc during remarking.
// * Reference discovery is MT (see below).
// * Reference discovery requires a barrier (see below).
// * Reference processing may or may not be MT
// (depending on the value of ParallelRefProcEnabled
// and ParallelGCThreads).
// * A full GC disables reference discovery by the CM
// ref processor and abandons any entries on it's
// discovered lists.
//
// * For the STW processor:
// * Non MT discovery is enabled at the start of a full GC.
// * Processing and enqueueing during a full GC is non-MT.
// * During a full GC, references are processed after marking.
//
// * Discovery (may or may not be MT) is enabled at the start
// of an incremental evacuation pause.
// * References are processed near the end of a STW evacuation pause.
// * For both types of GC:
// * Discovery is atomic - i.e. not concurrent.
// * Reference discovery will not need a barrier.
// Concurrent Mark ref processor
_ref_processor_cm =
new ReferenceProcessor(&_is_subject_to_discovery_cm,
ParallelGCThreads, // degree of mt processing
// We discover with the gc worker threads during Remark, so both
// thread counts must be considered for discovery.
MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
true, // Reference discovery is concurrent
&_is_alive_closure_cm); // is alive closure
// STW ref processor
_ref_processor_stw =
new ReferenceProcessor(&_is_subject_to_discovery_stw,
ParallelGCThreads, // degree of mt processing
ParallelGCThreads, // degree of mt discovery
false, // Reference discovery is not concurrent
&_is_alive_closure_stw); // is alive closure
}
SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
return &_soft_ref_policy;
}
size_t G1CollectedHeap::capacity() const {
return _hrm.length() * HeapRegion::GrainBytes;
}
size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
return _hrm.total_free_bytes();
}
// Computes the sum of the storage used by the various regions.
size_t G1CollectedHeap::used() const {
size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
return result;
}
size_t G1CollectedHeap::used_unlocked() const {
return _summary_bytes_used;
}
class SumUsedClosure: public HeapRegionClosure {
size_t _used;
public:
SumUsedClosure() : _used(0) {}
bool do_heap_region(HeapRegion* r) {
_used += r->used();
return false;
}
size_t result() { return _used; }
};
size_t G1CollectedHeap::recalculate_used() const {
SumUsedClosure blk;
heap_region_iterate(&blk);
return blk.result();
}
bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
return GCCause::is_user_requested_gc(cause) && ExplicitGCInvokesConcurrent;
}
bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
switch (cause) {
case GCCause::_g1_humongous_allocation: return true;
case GCCause::_g1_periodic_collection: return G1PeriodicGCInvokesConcurrent;
case GCCause::_wb_breakpoint: return true;
case GCCause::_codecache_GC_aggressive: return true;
case GCCause::_codecache_GC_threshold: return true;
default: return is_user_requested_concurrent_full_gc(cause);
}
}
void G1CollectedHeap::increment_old_marking_cycles_started() {
assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
_old_marking_cycles_started == _old_marking_cycles_completed + 1,
"Wrong marking cycle count (started: %d, completed: %d)",
_old_marking_cycles_started, _old_marking_cycles_completed);
_old_marking_cycles_started++;
}
void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent,
bool whole_heap_examined) {
MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
// We assume that if concurrent == true, then the caller is a
// concurrent thread that was joined the Suspendible Thread
// Set. If there's ever a cheap way to check this, we should add an
// assert here.
// Given that this method is called at the end of a Full GC or of a
// concurrent cycle, and those can be nested (i.e., a Full GC can
// interrupt a concurrent cycle), the number of full collections
// completed should be either one (in the case where there was no
// nesting) or two (when a Full GC interrupted a concurrent cycle)
// behind the number of full collections started.
// This is the case for the inner caller, i.e. a Full GC.
assert(concurrent ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 2),
"for inner caller (Full GC): _old_marking_cycles_started = %u "
"is inconsistent with _old_marking_cycles_completed = %u",
_old_marking_cycles_started, _old_marking_cycles_completed);
// This is the case for the outer caller, i.e. the concurrent cycle.
assert(!concurrent ||
(_old_marking_cycles_started == _old_marking_cycles_completed + 1),
"for outer caller (concurrent cycle): "
"_old_marking_cycles_started = %u "
"is inconsistent with _old_marking_cycles_completed = %u",
_old_marking_cycles_started, _old_marking_cycles_completed);
_old_marking_cycles_completed += 1;
if (whole_heap_examined) {
// Signal that we have completed a visit to all live objects.
record_whole_heap_examined_timestamp();
}
// We need to clear the "in_progress" flag in the CM thread before
// we wake up any waiters (especially when ExplicitInvokesConcurrent
// is set) so that if a waiter requests another System.gc() it doesn't
// incorrectly see that a marking cycle is still in progress.
if (concurrent) {
_cm_thread->set_idle();
}
// Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
// for a full GC to finish that their wait is over.
ml.notify_all();
}
// Helper for collect().
static G1GCCounters collection_counters(G1CollectedHeap* g1h) {
MutexLocker ml(Heap_lock);
return G1GCCounters(g1h);
}
void G1CollectedHeap::collect(GCCause::Cause cause) {
try_collect(cause, collection_counters(this));
}
// Return true if (x < y) with allowance for wraparound.
static bool gc_counter_less_than(uint x, uint y) {
return (x - y) > (UINT_MAX/2);
}
// LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
// Macro so msg printing is format-checked.
#define LOG_COLLECT_CONCURRENTLY(cause, ...) \
do { \
LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt; \
if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) { \
ResourceMark rm; /* For thread name. */ \
LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
Thread::current()->name(), \
GCCause::to_string(cause)); \
LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__); \
} \
} while (0)
#define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
uint gc_counter,
uint old_marking_started_before) {
assert_heap_not_locked();
assert(should_do_concurrent_full_gc(cause),
"Non-concurrent cause %s", GCCause::to_string(cause));
for (uint i = 1; true; ++i) {
// Try to schedule concurrent start evacuation pause that will
// start a concurrent cycle.
LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
VM_G1TryInitiateConcMark op(gc_counter, cause);
VMThread::execute(&op);
// Request is trivially finished.
if (cause == GCCause::_g1_periodic_collection) {
LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
return op.gc_succeeded();
}
// If VMOp skipped initiating concurrent marking cycle because
// we're terminating, then we're done.
if (op.terminating()) {
LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
return false;
}
// Lock to get consistent set of values.
uint old_marking_started_after;
uint old_marking_completed_after;
{
MutexLocker ml(Heap_lock);
// Update gc_counter for retrying VMOp if needed. Captured here to be
// consistent with the values we use below for termination tests. If
// a retry is needed after a possible wait, and another collection
// occurs in the meantime, it will cause our retry to be skipped and
// we'll recheck for termination with updated conditions from that
// more recent collection. That's what we want, rather than having
// our retry possibly perform an unnecessary collection.
gc_counter = total_collections();
old_marking_started_after = _old_marking_cycles_started;
old_marking_completed_after = _old_marking_cycles_completed;
}
if (cause == GCCause::_wb_breakpoint) {
if (op.gc_succeeded()) {
LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
return true;
}
// When _wb_breakpoint there can't be another cycle or deferred.
assert(!op.cycle_already_in_progress(), "invariant");
assert(!op.whitebox_attached(), "invariant");
// Concurrent cycle attempt might have been cancelled by some other
// collection, so retry. Unlike other cases below, we want to retry
// even if cancelled by a STW full collection, because we really want
// to start a concurrent cycle.
if (old_marking_started_before != old_marking_started_after) {
LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
old_marking_started_before = old_marking_started_after;
}
} else if (!GCCause::is_user_requested_gc(cause)) {
// For an "automatic" (not user-requested) collection, we just need to
// ensure that progress is made.
//
// Request is finished if any of
// (1) the VMOp successfully performed a GC,
// (2) a concurrent cycle was already in progress,
// (3) whitebox is controlling concurrent cycles,
// (4) a new cycle was started (by this thread or some other), or
// (5) a Full GC was performed.
// Cases (4) and (5) are detected together by a change to
// _old_marking_cycles_started.
//
// Note that (1) does not imply (4). If we're still in the mixed
// phase of an earlier concurrent collection, the request to make the
// collection a concurrent start won't be honored. If we don't check for
// both conditions we'll spin doing back-to-back collections.
if (op.gc_succeeded() ||
op.cycle_already_in_progress() ||
op.whitebox_attached() ||
(old_marking_started_before != old_marking_started_after)) {
LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
return true;
}
} else { // User-requested GC.
// For a user-requested collection, we want to ensure that a complete
// full collection has been performed before returning, but without
// waiting for more than needed.
// For user-requested GCs (unlike non-UR), a successful VMOp implies a
// new cycle was started. That's good, because it's not clear what we
// should do otherwise. Trying again just does back to back GCs.
// Can't wait for someone else to start a cycle. And returning fails
// to meet the goal of ensuring a full collection was performed.
assert(!op.gc_succeeded() ||
(old_marking_started_before != old_marking_started_after),
"invariant: succeeded %s, started before %u, started after %u",
BOOL_TO_STR(op.gc_succeeded()),
old_marking_started_before, old_marking_started_after);
// Request is finished if a full collection (concurrent or stw)
// was started after this request and has completed, e.g.
// started_before < completed_after.
if (gc_counter_less_than(old_marking_started_before,
old_marking_completed_after)) {
LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
return true;
}
if (old_marking_started_after != old_marking_completed_after) {
// If there is an in-progress cycle (possibly started by us), then
// wait for that cycle to complete, e.g.
// while completed_now < started_after.
LOG_COLLECT_CONCURRENTLY(cause, "wait");
MonitorLocker ml(G1OldGCCount_lock);
while (gc_counter_less_than(_old_marking_cycles_completed,
old_marking_started_after)) {
ml.wait();
}
// Request is finished if the collection we just waited for was
// started after this request.
if (old_marking_started_before != old_marking_started_after) {
LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
return true;
}
}
// If VMOp was successful then it started a new cycle that the above
// wait &etc should have recognized as finishing this request. This
// differs from a non-user-request, where gc_succeeded does not imply
// a new cycle was started.
assert(!op.gc_succeeded(), "invariant");
if (op.cycle_already_in_progress()) {
// If VMOp failed because a cycle was already in progress, it
// is now complete. But it didn't finish this user-requested
// GC, so try again.
LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
continue;
} else if (op.whitebox_attached()) {
// If WhiteBox wants control, wait for notification of a state
// change in the controller, then try again. Don't wait for
// release of control, since collections may complete while in
// control. Note: This won't recognize a STW full collection
// while waiting; we can't wait on multiple monitors.
LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
if (ConcurrentGCBreakpoints::is_controlled()) {
ml.wait();
}
continue;
}
}
// Collection failed and should be retried.
assert(op.transient_failure(), "invariant");
if (GCLocker::is_active_and_needs_gc()) {
// If GCLocker is active, wait until clear before retrying.
LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
GCLocker::stall_until_clear();
}
LOG_COLLECT_CONCURRENTLY(cause, "retry");
}
}
bool G1CollectedHeap::try_collect_fullgc(GCCause::Cause cause,
const G1GCCounters& counters_before) {
assert_heap_not_locked();
while(true) {
VM_G1CollectFull op(counters_before.total_collections(),
counters_before.total_full_collections(),
cause);
VMThread::execute(&op);
// Request is trivially finished.
if (!GCCause::is_explicit_full_gc(cause) || op.gc_succeeded()) {
return op.gc_succeeded();
}
{
MutexLocker ml(Heap_lock);
if (counters_before.total_full_collections() != total_full_collections()) {
return true;
}
}
if (GCLocker::is_active_and_needs_gc()) {
// If GCLocker is active, wait until clear before retrying.
GCLocker::stall_until_clear();
}
}
}
bool G1CollectedHeap::try_collect(GCCause::Cause cause,
const G1GCCounters& counters_before) {
if (should_do_concurrent_full_gc(cause)) {
return try_collect_concurrently(cause,
counters_before.total_collections(),
counters_before.old_marking_cycles_started());
} else if (GCLocker::should_discard(cause, counters_before.total_collections())) {
// Indicate failure to be consistent with VMOp failure due to
// another collection slipping in after our gc_count but before
// our request is processed.
return false;
} else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
// Schedule a standard evacuation pause. We're setting word_size
// to 0 which means that we are not requesting a post-GC allocation.
VM_G1CollectForAllocation op(0, /* word_size */
counters_before.total_collections(),
cause);
VMThread::execute(&op);
return op.gc_succeeded();
} else {
// Schedule a Full GC.
return try_collect_fullgc(cause, counters_before);
}
}
void G1CollectedHeap::start_concurrent_gc_for_metadata_allocation(GCCause::Cause gc_cause) {
GCCauseSetter x(this, gc_cause);
// At this point we are supposed to start a concurrent cycle. We
// will do so if one is not already in progress.
bool should_start = policy()->force_concurrent_start_if_outside_cycle(gc_cause);
if (should_start) {
do_collection_pause_at_safepoint();
}
}
bool G1CollectedHeap::is_in(const void* p) const {
return is_in_reserved(p) && _hrm.is_available(addr_to_region(p));
}
// Iteration functions.
// Iterates an ObjectClosure over all objects within a HeapRegion.
class IterateObjectClosureRegionClosure: public HeapRegionClosure {
ObjectClosure* _cl;
public:
IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
bool do_heap_region(HeapRegion* r) {
if (!r->is_continues_humongous()) {
r->object_iterate(_cl);
}
return false;
}
};
void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
IterateObjectClosureRegionClosure blk(cl);
heap_region_iterate(&blk);
}
class G1ParallelObjectIterator : public ParallelObjectIteratorImpl {
private:
G1CollectedHeap* _heap;
HeapRegionClaimer _claimer;
public:
G1ParallelObjectIterator(uint thread_num) :
_heap(G1CollectedHeap::heap()),
_claimer(thread_num == 0 ? G1CollectedHeap::heap()->workers()->active_workers() : thread_num) {}
virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
_heap->object_iterate_parallel(cl, worker_id, &_claimer);
}
};
ParallelObjectIteratorImpl* G1CollectedHeap::parallel_object_iterator(uint thread_num) {
return new G1ParallelObjectIterator(thread_num);
}
void G1CollectedHeap::object_iterate_parallel(ObjectClosure* cl, uint worker_id, HeapRegionClaimer* claimer) {
IterateObjectClosureRegionClosure blk(cl);
heap_region_par_iterate_from_worker_offset(&blk, claimer, worker_id);
}
void G1CollectedHeap::keep_alive(oop obj) {
G1BarrierSet::enqueue_preloaded(obj);
}
void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
_hrm.iterate(cl);
}
void G1CollectedHeap::heap_region_iterate(HeapRegionIndexClosure* cl) const {
_hrm.iterate(cl);
}
void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
HeapRegionClaimer *hrclaimer,
uint worker_id) const {
_hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
}
void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
HeapRegionClaimer *hrclaimer) const {
_hrm.par_iterate(cl, hrclaimer, 0);
}
void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
_collection_set.iterate(cl);
}
void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl,
HeapRegionClaimer* hr_claimer,
uint worker_id) {
_collection_set.par_iterate(cl, hr_claimer, worker_id);
}
void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl,
HeapRegionClaimer* hr_claimer,
uint worker_id) {
_collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id);
}
void G1CollectedHeap::par_iterate_regions_array(HeapRegionClosure* cl,
HeapRegionClaimer* hr_claimer,
const uint regions[],
size_t length,
uint worker_id) const {
assert_at_safepoint();
if (length == 0) {
return;
}
uint total_workers = workers()->active_workers();
size_t start_pos = (worker_id * length) / total_workers;
size_t cur_pos = start_pos;
do {
uint region_idx = regions[cur_pos];
if (hr_claimer == nullptr || hr_claimer->claim_region(region_idx)) {
HeapRegion* r = region_at(region_idx);
bool result = cl->do_heap_region(r);
guarantee(!result, "Must not cancel iteration");
}
cur_pos++;
if (cur_pos == length) {
cur_pos = 0;
}
} while (cur_pos != start_pos);
}
HeapWord* G1CollectedHeap::block_start(const void* addr) const {
HeapRegion* hr = heap_region_containing(addr);
// The CollectedHeap API requires us to not fail for any given address within
// the heap. HeapRegion::block_start() has been optimized to not accept addresses
// outside of the allocated area.
if (addr >= hr->top()) {
return nullptr;
}
return hr->block_start(addr);
}
bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
HeapRegion* hr = heap_region_containing(addr);
return hr->block_is_obj(addr, hr->parsable_bottom_acquire());
}
size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
}
size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
return _eden.length() * HeapRegion::GrainBytes;
}
// For G1 TLABs should not contain humongous objects, so the maximum TLAB size
// must be equal to the humongous object limit.
size_t G1CollectedHeap::max_tlab_size() const {
return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
}
size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
return _allocator->unsafe_max_tlab_alloc();
}
size_t G1CollectedHeap::max_capacity() const {
return max_regions() * HeapRegion::GrainBytes;
}
void G1CollectedHeap::prepare_for_verify() {
_verifier->prepare_for_verify();
}
void G1CollectedHeap::verify(VerifyOption vo) {
_verifier->verify(vo);
}
bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
return true;
}
class PrintRegionClosure: public HeapRegionClosure {
outputStream* _st;
public:
PrintRegionClosure(outputStream* st) : _st(st) {}
bool do_heap_region(HeapRegion* r) {
r->print_on(_st);
return false;
}
};
bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
const HeapRegion* hr,
const VerifyOption vo) const {
switch (vo) {
case VerifyOption::G1UseConcMarking: return is_obj_dead(obj, hr);
case VerifyOption::G1UseFullMarking: return is_obj_dead_full(obj, hr);
default: ShouldNotReachHere();
}
return false; // keep some compilers happy
}
bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
const VerifyOption vo) const {
switch (vo) {
case VerifyOption::G1UseConcMarking: return is_obj_dead(obj);
case VerifyOption::G1UseFullMarking: return is_obj_dead_full(obj);
default: ShouldNotReachHere();
}
return false; // keep some compilers happy
}
void G1CollectedHeap::pin_object(JavaThread* thread, oop obj) {
GCLocker::lock_critical(thread);
}
void G1CollectedHeap::unpin_object(JavaThread* thread, oop obj) {
GCLocker::unlock_critical(thread);
}
void G1CollectedHeap::print_heap_regions() const {
LogTarget(Trace, gc, heap, region) lt;
if (lt.is_enabled()) {
LogStream ls(lt);
print_regions_on(&ls);
}
}
void G1CollectedHeap::print_on(outputStream* st) const {
size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
st->print(" %-20s", "garbage-first heap");
st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
capacity()/K, heap_used/K);
st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
p2i(_hrm.reserved().start()),
p2i(_hrm.reserved().end()));
st->cr();
st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
uint young_regions = young_regions_count();
st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
(size_t) young_regions * HeapRegion::GrainBytes / K);
uint survivor_regions = survivor_regions_count();
st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
(size_t) survivor_regions * HeapRegion::GrainBytes / K);
st->cr();
if (_numa->is_enabled()) {
uint num_nodes = _numa->num_active_nodes();
st->print(" remaining free region(s) on each NUMA node: ");
const int* node_ids = _numa->node_ids();
for (uint node_index = 0; node_index < num_nodes; node_index++) {
uint num_free_regions = _hrm.num_free_regions(node_index);
st->print("%d=%u ", node_ids[node_index], num_free_regions);
}
st->cr();
}
MetaspaceUtils::print_on(st);
}
void G1CollectedHeap::print_regions_on(outputStream* st) const {
st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
"HS=humongous(starts), HC=humongous(continues), "
"CS=collection set, F=free, "
"TAMS=top-at-mark-start, "
"PB=parsable bottom");
PrintRegionClosure blk(st);
heap_region_iterate(&blk);
}
void G1CollectedHeap::print_extended_on(outputStream* st) const {
print_on(st);
// Print the per-region information.
st->cr();
print_regions_on(st);
}
void G1CollectedHeap::print_on_error(outputStream* st) const {
this->CollectedHeap::print_on_error(st);
if (_cm != nullptr) {
st->cr();
_cm->print_on_error(st);
}
}
void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
workers()->threads_do(tc);
tc->do_thread(_cm_thread);
_cm->threads_do(tc);
_cr->threads_do(tc);
tc->do_thread(_service_thread);
}
void G1CollectedHeap::print_tracing_info() const {
rem_set()->print_summary_info();
concurrent_mark()->print_summary_info();
}
bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
}
G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
size_t eden_used_bytes = _monitoring_support->eden_space_used();
size_t survivor_used_bytes = _monitoring_support->survivor_space_used();
size_t old_gen_used_bytes = _monitoring_support->old_gen_used();
size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
size_t eden_capacity_bytes =
(policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
VirtualSpaceSummary heap_summary = create_heap_space_summary();
return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, eden_capacity_bytes,
survivor_used_bytes, old_gen_used_bytes, num_regions());
}
G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
stats->unused(), stats->used(), stats->region_end_waste(),
stats->regions_filled(), stats->num_plab_filled(),
stats->direct_allocated(), stats->num_direct_allocated(),
stats->failure_used(), stats->failure_waste());
}
void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
const G1HeapSummary& heap_summary = create_g1_heap_summary();
gc_tracer->report_gc_heap_summary(when, heap_summary);
const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
gc_tracer->report_metaspace_summary(when, metaspace_summary);
}
void G1CollectedHeap::gc_prologue(bool full) {
assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
// Update common counters.
increment_total_collections(full /* full gc */);
if (full || collector_state()->in_concurrent_start_gc()) {
increment_old_marking_cycles_started();
}
}
void G1CollectedHeap::gc_epilogue(bool full) {
// Update common counters.
if (full) {
// Update the number of full collections that have been completed.
increment_old_marking_cycles_completed(false /* concurrent */, true /* liveness_completed */);
}
#if COMPILER2_OR_JVMCI
assert(DerivedPointerTable::is_empty(), "derived pointer present");
#endif
// We have just completed a GC. Update the soft reference
// policy with the new heap occupancy
Universe::heap()->update_capacity_and_used_at_gc();
_collection_pause_end = Ticks::now();
_free_arena_memory_task->notify_new_stats(&_young_gen_card_set_stats,
&_collection_set_candidates_card_set_stats);
}
uint G1CollectedHeap::uncommit_regions(uint region_limit) {
return _hrm.uncommit_inactive_regions(region_limit);
}
bool G1CollectedHeap::has_uncommittable_regions() {
return _hrm.has_inactive_regions();
}
void G1CollectedHeap::uncommit_regions_if_necessary() {
if (has_uncommittable_regions()) {
G1UncommitRegionTask::enqueue();
}
}
void G1CollectedHeap::verify_numa_regions(const char* desc) {
LogTarget(Trace, gc, heap, verify) lt;
if (lt.is_enabled()) {
LogStream ls(lt);
// Iterate all heap regions to print matching between preferred numa id and actual numa id.
G1NodeIndexCheckClosure cl(desc, _numa, &ls);
heap_region_iterate(&cl);
}
}
HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
uint gc_count_before,
bool* succeeded,
GCCause::Cause gc_cause) {
assert_heap_not_locked_and_not_at_safepoint();
VM_G1CollectForAllocation op(word_size, gc_count_before, gc_cause);
VMThread::execute(&op);
HeapWord* result = op.result();
bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
assert(result == nullptr || ret_succeeded,
"the result should be null if the VM did not succeed");
*succeeded = ret_succeeded;
assert_heap_not_locked();
return result;
}
void G1CollectedHeap::start_concurrent_cycle(bool concurrent_operation_is_full_mark) {
assert(!_cm_thread->in_progress(), "Can not start concurrent operation while in progress");
MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
if (concurrent_operation_is_full_mark) {
_cm->post_concurrent_mark_start();
_cm_thread->start_full_mark();
} else {
_cm->post_concurrent_undo_start();
_cm_thread->start_undo_mark();
}
CGC_lock->notify();
}
bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
// We don't nominate objects with many remembered set entries, on
// the assumption that such objects are likely still live.
HeapRegionRemSet* rem_set = r->rem_set();
return rem_set->occupancy_less_or_equal_than(G1EagerReclaimRemSetThreshold);
}
#ifndef PRODUCT
void G1CollectedHeap::verify_region_attr_remset_is_tracked() {
class VerifyRegionAttrRemSet : public HeapRegionClosure {
public:
virtual bool do_heap_region(HeapRegion* r) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
bool const remset_is_tracked = g1h->region_attr(r->bottom()).remset_is_tracked();
assert(r->rem_set()->is_tracked() == remset_is_tracked,
"Region %u remset tracking status (%s) different to region attribute (%s)",
r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(remset_is_tracked));
return false;
}
} cl;
heap_region_iterate(&cl);
}
#endif
void G1CollectedHeap::start_new_collection_set() {
collection_set()->start_incremental_building();
clear_region_attr();
guarantee(_eden.length() == 0, "eden should have been cleared");
policy()->transfer_survivors_to_cset(survivor());
// We redo the verification but now wrt to the new CSet which
// has just got initialized after the previous CSet was freed.
_cm->verify_no_collection_set_oops();
}
G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
if (collector_state()->in_concurrent_start_gc()) {
return G1HeapVerifier::G1VerifyConcurrentStart;
} else if (collector_state()->in_young_only_phase()) {
return G1HeapVerifier::G1VerifyYoungNormal;
} else {
return G1HeapVerifier::G1VerifyMixed;
}
}
void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
if (!VerifyBeforeGC) {
return;
}
if (!G1HeapVerifier::should_verify(type)) {
return;
}
Ticks start = Ticks::now();
_verifier->prepare_for_verify();
_verifier->verify_region_sets_optional();
_verifier->verify_dirty_young_regions();
_verifier->verify_before_gc();
verify_numa_regions("GC Start");
phase_times()->record_verify_before_time_ms((Ticks::now() - start).seconds() * MILLIUNITS);
}
void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
if (!VerifyAfterGC) {
return;
}
if (!G1HeapVerifier::should_verify(type)) {
return;
}
Ticks start = Ticks::now();
_verifier->verify_after_gc();
verify_numa_regions("GC End");
_verifier->verify_region_sets_optional();
phase_times()->record_verify_after_time_ms((Ticks::now() - start).seconds() * MILLIUNITS);
}
void G1CollectedHeap::expand_heap_after_young_collection(){
size_t expand_bytes = _heap_sizing_policy->young_collection_expansion_amount();
if (expand_bytes > 0) {
// No need for an ergo logging here,
// expansion_amount() does this when it returns a value > 0.
double expand_ms = 0.0;
if (!expand(expand_bytes, _workers, &expand_ms)) {
// We failed to expand the heap. Cannot do anything about it.
}
phase_times()->record_expand_heap_time(expand_ms);
}
}
bool G1CollectedHeap::do_collection_pause_at_safepoint() {
assert_at_safepoint_on_vm_thread();
guarantee(!is_gc_active(), "collection is not reentrant");
if (GCLocker::check_active_before_gc()) {
return false;
}
do_collection_pause_at_safepoint_helper();
return true;
}
G1HeapPrinterMark::G1HeapPrinterMark(G1CollectedHeap* g1h) : _g1h(g1h), _heap_transition(g1h) {
// This summary needs to be printed before incrementing total collections.
_g1h->rem_set()->print_periodic_summary_info("Before GC RS summary",
_g1h->total_collections(),
true /* show_thread_times */);
_g1h->print_heap_before_gc();
_g1h->print_heap_regions();
}
G1HeapPrinterMark::~G1HeapPrinterMark() {
_g1h->policy()->print_age_table();
_g1h->rem_set()->print_coarsen_stats();
// We are at the end of the GC. Total collections has already been increased.
_g1h->rem_set()->print_periodic_summary_info("After GC RS summary",
_g1h->total_collections() - 1,
false /* show_thread_times */);
_heap_transition.print();
_g1h->print_heap_regions();
_g1h->print_heap_after_gc();
// Print NUMA statistics.
_g1h->numa()->print_statistics();
}
G1JFRTracerMark::G1JFRTracerMark(STWGCTimer* timer, GCTracer* tracer) :
_timer(timer), _tracer(tracer) {
_timer->register_gc_start();
_tracer->report_gc_start(G1CollectedHeap::heap()->gc_cause(), _timer->gc_start());
G1CollectedHeap::heap()->trace_heap_before_gc(_tracer);
}
G1JFRTracerMark::~G1JFRTracerMark() {
G1CollectedHeap::heap()->trace_heap_after_gc(_tracer);
_timer->register_gc_end();
_tracer->report_gc_end(_timer->gc_end(), _timer->time_partitions());
}
void G1CollectedHeap::prepare_for_mutator_after_young_collection() {
Ticks start = Ticks::now();
_survivor_evac_stats.adjust_desired_plab_size();
_old_evac_stats.adjust_desired_plab_size();
// Start a new incremental collection set for the mutator phase.
start_new_collection_set();
_allocator->init_mutator_alloc_regions();
phase_times()->record_prepare_for_mutator_time_ms((Ticks::now() - start).seconds() * 1000.0);
}
void G1CollectedHeap::retire_tlabs() {
ensure_parsability(true);
}
void G1CollectedHeap::do_collection_pause_at_safepoint_helper() {
ResourceMark rm;
IsGCActiveMark active_gc_mark;
GCIdMark gc_id_mark;
SvcGCMarker sgcm(SvcGCMarker::MINOR);
GCTraceCPUTime tcpu(_gc_tracer_stw);
_bytes_used_during_gc = 0;
policy()->decide_on_concurrent_start_pause();
// Record whether this pause may need to trigger a concurrent operation. Later,
// when we signal the G1ConcurrentMarkThread, the collector state has already
// been reset for the next pause.
bool should_start_concurrent_mark_operation = collector_state()->in_concurrent_start_gc();
// Perform the collection.
G1YoungCollector collector(gc_cause());
collector.collect();
// It should now be safe to tell the concurrent mark thread to start
// without its logging output interfering with the logging output
// that came from the pause.
if (should_start_concurrent_mark_operation) {
verifier()->verify_bitmap_clear(true /* above_tams_only */);
// CAUTION: after the start_concurrent_cycle() call below, the concurrent marking
// thread(s) could be running concurrently with us. Make sure that anything
// after this point does not assume that we are the only GC thread running.
// Note: of course, the actual marking work will not start until the safepoint
// itself is released in SuspendibleThreadSet::desynchronize().
start_concurrent_cycle(collector.concurrent_operation_is_full_mark());
ConcurrentGCBreakpoints::notify_idle_to_active();
}
}
void G1CollectedHeap::complete_cleaning(bool class_unloading_occurred) {
uint num_workers = workers()->active_workers();
G1ParallelCleaningTask unlink_task(num_workers, class_unloading_occurred);
workers()->run_task(&unlink_task);
}
void G1CollectedHeap::unload_classes_and_code(const char* description, BoolObjectClosure* is_alive, GCTimer* timer) {
GCTraceTime(Debug, gc, phases) debug(description, timer);
ClassUnloadingContext ctx(workers()->active_workers(),
false /* unregister_nmethods_during_purge */,
false /* lock_codeblob_free_separately */);
{
CodeCache::UnlinkingScope scope(is_alive);
bool unloading_occurred = SystemDictionary::do_unloading(timer);
GCTraceTime(Debug, gc, phases) t("G1 Complete Cleaning", timer);
complete_cleaning(unloading_occurred);
}
{
GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", timer);
ctx.purge_nmethods();
}
{
GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", timer);
G1CollectedHeap::heap()->bulk_unregister_nmethods();
}
{
GCTraceTime(Debug, gc, phases) t("Free Code Blobs", timer);
ctx.free_code_blobs();
}
{
GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", timer);
ClassLoaderDataGraph::purge(true /* at_safepoint */);
DEBUG_ONLY(MetaspaceUtils::verify();)
}
}
class G1BulkUnregisterNMethodTask : public WorkerTask {
HeapRegionClaimer _hrclaimer;
class UnregisterNMethodsHeapRegionClosure : public HeapRegionClosure {
public:
bool do_heap_region(HeapRegion* hr) {
hr->rem_set()->bulk_remove_code_roots();
return false;
}
} _cl;
public:
G1BulkUnregisterNMethodTask(uint num_workers)
: WorkerTask("G1 Remove Unlinked NMethods From Code Root Set Task"),
_hrclaimer(num_workers) { }
void work(uint worker_id) {
G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hrclaimer, worker_id);
}
};
void G1CollectedHeap::bulk_unregister_nmethods() {
uint num_workers = workers()->active_workers();
G1BulkUnregisterNMethodTask t(num_workers);
workers()->run_task(&t);
}
bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
assert(obj != nullptr, "must not be null");
assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
// The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
// may falsely indicate that this is not the case here: however the collection set only
// contains old regions when concurrent mark is not running.
return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
}
void G1CollectedHeap::make_pending_list_reachable() {
if (collector_state()->in_concurrent_start_gc()) {
oop pll_head = Universe::reference_pending_list();
if (pll_head != nullptr) {
// Any valid worker id is fine here as we are in the VM thread and single-threaded.
_cm->mark_in_bitmap(0 /* worker_id */, pll_head);
}
}
}
void G1CollectedHeap::set_humongous_stats(uint num_humongous_total, uint num_humongous_candidates) {
_num_humongous_objects = num_humongous_total;
_num_humongous_reclaim_candidates = num_humongous_candidates;
}
bool G1CollectedHeap::should_sample_collection_set_candidates() const {
const G1CollectionSetCandidates* candidates = collection_set()->candidates();
return !candidates->is_empty();
}
void G1CollectedHeap::set_collection_set_candidates_stats(G1MonotonicArenaMemoryStats& stats) {
_collection_set_candidates_card_set_stats = stats;
}
void G1CollectedHeap::set_young_gen_card_set_stats(const G1MonotonicArenaMemoryStats& stats) {
_young_gen_card_set_stats = stats;
}
void G1CollectedHeap::record_obj_copy_mem_stats() {
policy()->old_gen_alloc_tracker()->
add_allocated_bytes_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
_gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
create_g1_evac_summary(&_old_evac_stats));
}
void G1CollectedHeap::clear_bitmap_for_region(HeapRegion* hr) {
concurrent_mark()->clear_bitmap_for_region(hr);
}
void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
assert(!hr->is_free(), "the region should not be free");
assert(!hr->is_empty(), "the region should not be empty");
assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
// Reset region metadata to allow reuse.
hr->hr_clear(true /* clear_space */);
_policy->remset_tracker()->update_at_free(hr);
if (free_list != nullptr) {
free_list->add_ordered(hr);
}
}
void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
FreeRegionList* free_list) {
assert(hr->is_humongous(), "this is only for humongous regions");
hr->clear_humongous();
free_region(hr, free_list);
}
void G1CollectedHeap::remove_from_old_gen_sets(const uint old_regions_removed,
const uint humongous_regions_removed) {
if (old_regions_removed > 0 || humongous_regions_removed > 0) {
MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
_old_set.bulk_remove(old_regions_removed);
_humongous_set.bulk_remove(humongous_regions_removed);
}
}
void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
assert(list != nullptr, "list can't be null");
if (!list->is_empty()) {
MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
_hrm.insert_list_into_free_list(list);
}
}
void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
decrease_used(bytes);
}
void G1CollectedHeap::clear_eden() {
_eden.clear();
}
void G1CollectedHeap::clear_collection_set() {
collection_set()->clear();
}
void G1CollectedHeap::rebuild_free_region_list() {
Ticks start = Ticks::now();
_hrm.rebuild_free_list(workers());
phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - start).seconds() * 1000.0);
}
class G1AbandonCollectionSetClosure : public HeapRegionClosure {
public:
virtual bool do_heap_region(HeapRegion* r) {
assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
G1CollectedHeap::heap()->clear_region_attr(r);
r->clear_young_index_in_cset();
return false;
}
};
void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
G1AbandonCollectionSetClosure cl;
collection_set_iterate_all(&cl);
collection_set->clear();
collection_set->stop_incremental_building();
}
bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
return _allocator->is_retained_old_region(hr);
}
void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
_eden.add(hr);
_policy->set_region_eden(hr);
}
#ifdef ASSERT
class NoYoungRegionsClosure: public HeapRegionClosure {
private:
bool _success;
public:
NoYoungRegionsClosure() : _success(true) { }
bool do_heap_region(HeapRegion* r) {
if (r->is_young()) {
log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
p2i(r->bottom()), p2i(r->end()));
_success = false;
}
return false;
}
bool success() { return _success; }
};
bool G1CollectedHeap::check_young_list_empty() {
bool ret = (young_regions_count() == 0);
NoYoungRegionsClosure closure;
heap_region_iterate(&closure);
ret = ret && closure.success();
return ret;
}
#endif // ASSERT
// Remove the given HeapRegion from the appropriate region set.
void G1CollectedHeap::prepare_region_for_full_compaction(HeapRegion* hr) {
if (hr->is_humongous()) {
_humongous_set.remove(hr);
} else if (hr->is_old()) {
_old_set.remove(hr);
} else if (hr->is_young()) {
// Note that emptying the eden and survivor lists is postponed and instead
// done as the first step when rebuilding the regions sets again. The reason
// for this is that during a full GC string deduplication needs to know if
// a collected region was young or old when the full GC was initiated.
hr->uninstall_surv_rate_group();
} else {
// We ignore free regions, we'll empty the free list afterwards.
assert(hr->is_free(), "it cannot be another type");
}
}
void G1CollectedHeap::increase_used(size_t bytes) {
_summary_bytes_used += bytes;
}
void G1CollectedHeap::decrease_used(size_t bytes) {
assert(_summary_bytes_used >= bytes,
"invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
_summary_bytes_used, bytes);
_summary_bytes_used -= bytes;
}
void G1CollectedHeap::set_used(size_t bytes) {
_summary_bytes_used = bytes;
}
class RebuildRegionSetsClosure : public HeapRegionClosure {
private:
bool _free_list_only;
HeapRegionSet* _old_set;
HeapRegionSet* _humongous_set;
HeapRegionManager* _hrm;
size_t _total_used;
public:
RebuildRegionSetsClosure(bool free_list_only,
HeapRegionSet* old_set,
HeapRegionSet* humongous_set,
HeapRegionManager* hrm) :
_free_list_only(free_list_only), _old_set(old_set),
_humongous_set(humongous_set), _hrm(hrm), _total_used(0) {
assert(_hrm->num_free_regions() == 0, "pre-condition");
if (!free_list_only) {
assert(_old_set->is_empty(), "pre-condition");
assert(_humongous_set->is_empty(), "pre-condition");
}
}
bool do_heap_region(HeapRegion* r) {
if (r->is_empty()) {
assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
// Add free regions to the free list
r->set_free();
_hrm->insert_into_free_list(r);
} else if (!_free_list_only) {
assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
if (r->is_humongous()) {
_humongous_set->add(r);
} else {
assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
// We now move all (non-humongous, non-old) regions to old gen,
// and register them as such.
r->move_to_old();
_old_set->add(r);
}
_total_used += r->used();
}
return false;
}
size_t total_used() {
return _total_used;
}
};
void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
assert_at_safepoint_on_vm_thread();
if (!free_list_only) {
_eden.clear();
_survivor.clear();
}
RebuildRegionSetsClosure cl(free_list_only,
&_old_set, &_humongous_set,
&_hrm);
heap_region_iterate(&cl);
if (!free_list_only) {
set_used(cl.total_used());
}
assert_used_and_recalculate_used_equal(this);
}
// Methods for the mutator alloc region
HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
bool force,
uint node_index) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
bool should_allocate = policy()->should_allocate_mutator_region();
if (force || should_allocate) {
HeapRegion* new_alloc_region = new_region(word_size,
HeapRegionType::Eden,
false /* do_expand */,
node_index);
if (new_alloc_region != nullptr) {
set_region_short_lived_locked(new_alloc_region);
_hr_printer.alloc(new_alloc_region, !should_allocate);
_policy->remset_tracker()->update_at_allocate(new_alloc_region);
return new_alloc_region;
}
}
return nullptr;
}
void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes) {
assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
collection_set()->add_eden_region(alloc_region);
increase_used(allocated_bytes);
_eden.add_used_bytes(allocated_bytes);
_hr_printer.retire(alloc_region);
// We update the eden sizes here, when the region is retired,
// instead of when it's allocated, since this is the point that its
// used space has been recorded in _summary_bytes_used.
monitoring_support()->update_eden_size();
}
// Methods for the GC alloc regions
bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
if (dest.is_old()) {
return true;
} else {
return survivor_regions_count() < policy()->max_survivor_regions();
}
}
HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
assert(FreeList_lock->owned_by_self(), "pre-condition");
if (!has_more_regions(dest)) {
return nullptr;
}
HeapRegionType type;
if (dest.is_young()) {
type = HeapRegionType::Survivor;
} else {
type = HeapRegionType::Old;
}
HeapRegion* new_alloc_region = new_region(word_size,
type,
true /* do_expand */,
node_index);
if (new_alloc_region != nullptr) {
if (type.is_survivor()) {
new_alloc_region->set_survivor();
_survivor.add(new_alloc_region);
register_new_survivor_region_with_region_attr(new_alloc_region);
} else {
new_alloc_region->set_old();
}
_policy->remset_tracker()->update_at_allocate(new_alloc_region);
register_region_with_region_attr(new_alloc_region);
_hr_printer.alloc(new_alloc_region);
return new_alloc_region;
}
return nullptr;
}
void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
size_t allocated_bytes,
G1HeapRegionAttr dest) {
_bytes_used_during_gc += allocated_bytes;
if (dest.is_old()) {
old_set_add(alloc_region);
} else {
assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
_survivor.add_used_bytes(allocated_bytes);
}
bool const during_im = collector_state()->in_concurrent_start_gc();
if (during_im && allocated_bytes > 0) {
_cm->add_root_region(alloc_region);
}
_hr_printer.retire(alloc_region);
}
HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
bool expanded = false;
uint index = _hrm.find_highest_free(&expanded);
if (index != G1_NO_HRM_INDEX) {
if (expanded) {
log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
HeapRegion::GrainWords * HeapWordSize);
}
return _hrm.allocate_free_regions_starting_at(index, 1);
}
return nullptr;
}
void G1CollectedHeap::mark_evac_failure_object(uint worker_id, const oop obj, size_t obj_size) const {
assert(!_cm->is_marked_in_bitmap(obj), "must be");
_cm->raw_mark_in_bitmap(obj);
if (collector_state()->in_concurrent_start_gc()) {
_cm->add_to_liveness(worker_id, obj, obj_size);
}
}
// Optimized nmethod scanning
class RegisterNMethodOopClosure: public OopClosure {
G1CollectedHeap* _g1h;
nmethod* _nm;
public:
RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
_g1h(g1h), _nm(nm) {}
void do_oop(oop* p) {
oop heap_oop = RawAccess<>::oop_load(p);
if (!CompressedOops::is_null(heap_oop)) {
oop obj = CompressedOops::decode_not_null(heap_oop);
HeapRegion* hr = _g1h->heap_region_containing(obj);
assert(!hr->is_continues_humongous(),
"trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
" starting at " HR_FORMAT,
p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
hr->add_code_root(_nm);
}
}
void do_oop(narrowOop* p) { ShouldNotReachHere(); }
};
void G1CollectedHeap::register_nmethod(nmethod* nm) {
guarantee(nm != nullptr, "sanity");
RegisterNMethodOopClosure reg_cl(this, nm);
nm->oops_do(&reg_cl);
}
void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
// We always unregister nmethods in bulk during code unloading only.
ShouldNotReachHere();
}
void G1CollectedHeap::update_used_after_gc(bool evacuation_failed) {
if (evacuation_failed) {
// Reset the G1EvacuationFailureALot counters and flags
evac_failure_injector()->reset();
set_used(recalculate_used());
} else {
// The "used" of the collection set have already been subtracted
// when they were freed. Add in the bytes used.
increase_used(_bytes_used_during_gc);
}
}
class RebuildCodeRootClosure: public CodeBlobClosure {
G1CollectedHeap* _g1h;
public:
RebuildCodeRootClosure(G1CollectedHeap* g1h) :
_g1h(g1h) {}
void do_code_blob(CodeBlob* cb) {
nmethod* nm = cb->as_nmethod_or_null();
if (nm != nullptr) {
_g1h->register_nmethod(nm);
}
}
};
void G1CollectedHeap::rebuild_code_roots() {
RebuildCodeRootClosure blob_cl(this);
CodeCache::blobs_do(&blob_cl);
}
void G1CollectedHeap::initialize_serviceability() {
_monitoring_support->initialize_serviceability();
}
MemoryUsage G1CollectedHeap::memory_usage() {
return _monitoring_support->memory_usage();
}
GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
return _monitoring_support->memory_managers();
}
GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
return _monitoring_support->memory_pools();
}
void G1CollectedHeap::fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap) {
HeapRegion* region = heap_region_containing(start);
region->fill_with_dummy_object(start, pointer_delta(end, start), zap);
}
void G1CollectedHeap::start_codecache_marking_cycle_if_inactive(bool concurrent_mark_start) {
// We can reach here with an active code cache marking cycle either because the
// previous G1 concurrent marking cycle was undone (if heap occupancy after the
// concurrent start young collection was below the threshold) or aborted. See
// CodeCache::on_gc_marking_cycle_finish() why this is. We must not start a new code
// cache cycle then. If we are about to start a new g1 concurrent marking cycle we
// still have to arm all nmethod entry barriers. They are needed for adding oop
// constants to the SATB snapshot. Full GC does not need nmethods to be armed.
if (!CodeCache::is_gc_marking_cycle_active()) {
CodeCache::on_gc_marking_cycle_start();
}
if (concurrent_mark_start) {
CodeCache::arm_all_nmethods();
}
}
void G1CollectedHeap::finish_codecache_marking_cycle() {
CodeCache::on_gc_marking_cycle_finish();
CodeCache::arm_all_nmethods();
}