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third-party-mirror/openjdk/jdk25u/2bb13dd57c55f0b23599aadb6d34d72abafe4b76/./src/hotspot/share/gc/parallel/psParallelCompact.cpp
blob: 79a0b898a6b7b121738051ba7f3012722078904a [file]
/*
* Copyright (c) 2005, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
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*/
#include "classfile/classLoaderDataGraph.hpp"
#include "classfile/javaClasses.inline.hpp"
#include "classfile/stringTable.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "compiler/oopMap.hpp"
#include "gc/parallel/objectStartArray.inline.hpp"
#include "gc/parallel/parallelArguments.hpp"
#include "gc/parallel/parallelScavengeHeap.inline.hpp"
#include "gc/parallel/parMarkBitMap.inline.hpp"
#include "gc/parallel/psAdaptiveSizePolicy.hpp"
#include "gc/parallel/psCompactionManager.inline.hpp"
#include "gc/parallel/psOldGen.hpp"
#include "gc/parallel/psParallelCompact.inline.hpp"
#include "gc/parallel/psPromotionManager.inline.hpp"
#include "gc/parallel/psRootType.hpp"
#include "gc/parallel/psScavenge.hpp"
#include "gc/parallel/psStringDedup.hpp"
#include "gc/parallel/psYoungGen.hpp"
#include "gc/shared/classUnloadingContext.hpp"
#include "gc/shared/fullGCForwarding.inline.hpp"
#include "gc/shared/gcCause.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.hpp"
#include "gc/shared/gcTimer.hpp"
#include "gc/shared/gcTrace.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "gc/shared/gcVMOperations.hpp"
#include "gc/shared/isGCActiveMark.hpp"
#include "gc/shared/oopStorage.inline.hpp"
#include "gc/shared/oopStorageSet.inline.hpp"
#include "gc/shared/oopStorageSetParState.inline.hpp"
#include "gc/shared/preservedMarks.inline.hpp"
#include "gc/shared/referencePolicy.hpp"
#include "gc/shared/referenceProcessor.hpp"
#include "gc/shared/referenceProcessorPhaseTimes.hpp"
#include "gc/shared/spaceDecorator.hpp"
#include "gc/shared/strongRootsScope.hpp"
#include "gc/shared/taskTerminator.hpp"
#include "gc/shared/weakProcessor.inline.hpp"
#include "gc/shared/workerPolicy.hpp"
#include "gc/shared/workerThread.hpp"
#include "gc/shared/workerUtils.hpp"
#include "logging/log.hpp"
#include "memory/iterator.inline.hpp"
#include "memory/memoryReserver.hpp"
#include "memory/metaspaceUtils.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "nmt/memTracker.hpp"
#include "oops/access.inline.hpp"
#include "oops/instanceClassLoaderKlass.inline.hpp"
#include "oops/instanceKlass.inline.hpp"
#include "oops/instanceMirrorKlass.inline.hpp"
#include "oops/methodData.hpp"
#include "oops/objArrayKlass.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/threads.hpp"
#include "runtime/vmThread.hpp"
#include "services/memoryService.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"
#include "utilities/events.hpp"
#include "utilities/formatBuffer.hpp"
#include "utilities/macros.hpp"
#include "utilities/stack.inline.hpp"
#if INCLUDE_JVMCI
#include "jvmci/jvmci.hpp"
#endif
#include <math.h>
// All sizes are in HeapWords.
const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
const size_t ParallelCompactData::RegionSizeBytes =
RegionSize << LogHeapWordSize;
const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_shift = 27;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::los_mask = ~dc_mask;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
bool ParallelCompactData::RegionData::is_clear() {
return (_destination == nullptr) &&
(_source_region == 0) &&
(_partial_obj_addr == nullptr) &&
(_partial_obj_size == 0) &&
(_dc_and_los == 0) &&
(_shadow_state == 0);
}
#ifdef ASSERT
void ParallelCompactData::RegionData::verify_clear() {
assert(_destination == nullptr, "inv");
assert(_source_region == 0, "inv");
assert(_partial_obj_addr == nullptr, "inv");
assert(_partial_obj_size == 0, "inv");
assert(_dc_and_los == 0, "inv");
assert(_shadow_state == 0, "inv");
}
#endif
SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
assert(split_region_idx != 0, "precondition");
// Obj denoted by split_point will be deferred to the next space.
assert(split_point != nullptr, "precondition");
const ParallelCompactData& sd = PSParallelCompact::summary_data();
PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
assert(preceding_live_words < split_region_ptr->data_size(), "inv");
HeapWord* preceding_destination = split_region_ptr->destination();
assert(preceding_destination != nullptr, "inv");
// How many regions does the preceding part occupy
uint preceding_destination_count;
if (preceding_live_words == 0) {
preceding_destination_count = 0;
} else {
// -1 so that the ending address doesn't fall on the region-boundary
if (sd.region_align_down(preceding_destination) ==
sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
preceding_destination_count = 1;
} else {
preceding_destination_count = 2;
}
}
_split_region_idx = split_region_idx;
_split_point = split_point;
_preceding_live_words = preceding_live_words;
_preceding_destination = preceding_destination;
_preceding_destination_count = preceding_destination_count;
}
void SplitInfo::clear()
{
_split_region_idx = 0;
_split_point = nullptr;
_preceding_live_words = 0;
_preceding_destination = nullptr;
_preceding_destination_count = 0;
assert(!is_valid(), "sanity");
}
#ifdef ASSERT
void SplitInfo::verify_clear()
{
assert(_split_region_idx == 0, "not clear");
assert(_split_point == nullptr, "not clear");
assert(_preceding_live_words == 0, "not clear");
assert(_preceding_destination == nullptr, "not clear");
assert(_preceding_destination_count == 0, "not clear");
}
#endif // #ifdef ASSERT
void PSParallelCompact::print_on(outputStream* st) {
_mark_bitmap.print_on(st);
}
ParallelCompactData::ParallelCompactData() :
_heap_start(nullptr),
DEBUG_ONLY(_heap_end(nullptr) COMMA)
_region_vspace(nullptr),
_reserved_byte_size(0),
_region_data(nullptr),
_region_count(0) {}
bool ParallelCompactData::initialize(MemRegion reserved_heap)
{
_heap_start = reserved_heap.start();
const size_t heap_size = reserved_heap.word_size();
DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
assert(region_align_down(_heap_start) == _heap_start,
"region start not aligned");
return initialize_region_data(heap_size);
}
PSVirtualSpace*
ParallelCompactData::create_vspace(size_t count, size_t element_size)
{
const size_t raw_bytes = count * element_size;
const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
const size_t granularity = os::vm_allocation_granularity();
const size_t rs_align = MAX2(page_sz, granularity);
_reserved_byte_size = align_up(raw_bytes, rs_align);
ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
rs_align,
page_sz,
mtGC);
if (!rs.is_reserved()) {
// Failed to reserve memory.
return nullptr;
}
os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
rs.size(), page_sz);
MemTracker::record_virtual_memory_tag(rs, mtGC);
PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
if (!vspace->expand_by(_reserved_byte_size)) {
// Failed to commit memory.
delete vspace;
// Release memory reserved in the space.
MemoryReserver::release(rs);
return nullptr;
}
return vspace;
}
bool ParallelCompactData::initialize_region_data(size_t heap_size)
{
assert(is_aligned(heap_size, RegionSize), "precondition");
const size_t count = heap_size >> Log2RegionSize;
_region_vspace = create_vspace(count, sizeof(RegionData));
if (_region_vspace != nullptr) {
_region_data = (RegionData*)_region_vspace->reserved_low_addr();
_region_count = count;
return true;
}
return false;
}
void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
assert(beg_region <= _region_count, "beg_region out of range");
assert(end_region <= _region_count, "end_region out of range");
const size_t region_cnt = end_region - beg_region;
memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
}
void
ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
{
assert(is_region_aligned(beg), "not RegionSize aligned");
assert(is_region_aligned(end), "not RegionSize aligned");
size_t cur_region = addr_to_region_idx(beg);
const size_t end_region = addr_to_region_idx(end);
HeapWord* addr = beg;
while (cur_region < end_region) {
_region_data[cur_region].set_destination(addr);
_region_data[cur_region].set_destination_count(0);
_region_data[cur_region].set_source_region(cur_region);
// Update live_obj_size so the region appears completely full.
size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
_region_data[cur_region].set_live_obj_size(live_size);
++cur_region;
addr += RegionSize;
}
}
// The total live words on src_region would overflow the target space, so find
// the overflowing object and record the split point. The invariant is that an
// obj should not cross space boundary.
HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
SplitInfo& split_info,
HeapWord* const destination,
HeapWord* const target_end,
HeapWord** target_next) {
assert(destination <= target_end, "sanity");
assert(destination + _region_data[src_region].data_size() > target_end,
"region should not fit into target space");
assert(is_region_aligned(target_end), "sanity");
size_t partial_obj_size = _region_data[src_region].partial_obj_size();
if (destination + partial_obj_size > target_end) {
assert(partial_obj_size > 0, "inv");
// The overflowing obj is from a previous region.
//
// source-regions:
//
// ***************
// | A|AA |
// ***************
// ^
// | split-point
//
// dest-region:
//
// ********
// |~~~~A |
// ********
// ^^
// || target-space-end
// |
// | destination
//
// AAA would overflow target-space.
//
HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
size_t split_region = addr_to_region_idx(overflowing_obj);
// The number of live words before the overflowing object on this split region
size_t preceding_live_words;
if (is_region_aligned(overflowing_obj)) {
preceding_live_words = 0;
} else {
// Words accounted by the overflowing object on the split region
size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
preceding_live_words = region(split_region)->data_size() - overflowing_size;
}
split_info.record(split_region, overflowing_obj, preceding_live_words);
// The [overflowing_obj, src_region_start) part has been accounted for, so
// must move back the new_top, now that this overflowing obj is deferred.
HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
// If the overflowing obj was relocated to its original destination,
// those destination regions would have their source_region set. Now that
// this overflowing obj is relocated somewhere else, reset the
// source_region.
{
size_t range_start = addr_to_region_idx(region_align_up(new_top));
size_t range_end = addr_to_region_idx(region_align_up(destination));
for (size_t i = range_start; i < range_end; ++i) {
region(i)->set_source_region(0);
}
}
// Update new top of target space
*target_next = new_top;
return overflowing_obj;
}
// Obj-iteration to locate the overflowing obj
HeapWord* region_start = region_to_addr(src_region);
HeapWord* region_end = region_start + RegionSize;
HeapWord* cur_addr = region_start + partial_obj_size;
size_t live_words = partial_obj_size;
while (true) {
assert(cur_addr < region_end, "inv");
cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
// There must be an overflowing obj in this region
assert(cur_addr < region_end, "inv");
oop obj = cast_to_oop(cur_addr);
size_t obj_size = obj->size();
if (destination + live_words + obj_size > target_end) {
// Found the overflowing obj
split_info.record(src_region, cur_addr, live_words);
*target_next = destination + live_words;
return cur_addr;
}
live_words += obj_size;
cur_addr += obj_size;
}
}
size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
HeapWord** full_region_prefix_end) {
size_t cur_region = addr_to_region_idx(space->bottom());
const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
size_t live_words = 0;
if (full_region_prefix_end == nullptr) {
for (/* empty */; cur_region < end_region; ++cur_region) {
live_words += _region_data[cur_region].data_size();
}
} else {
bool first_set = false;
for (/* empty */; cur_region < end_region; ++cur_region) {
size_t live_words_in_region = _region_data[cur_region].data_size();
if (!first_set && live_words_in_region < RegionSize) {
*full_region_prefix_end = region_to_addr(cur_region);
first_set = true;
}
live_words += live_words_in_region;
}
if (!first_set) {
// All regions are full of live objs.
assert(is_region_aligned(space->top()), "inv");
*full_region_prefix_end = space->top();
}
assert(*full_region_prefix_end != nullptr, "postcondition");
assert(is_region_aligned(*full_region_prefix_end), "inv");
assert(*full_region_prefix_end >= space->bottom(), "in-range");
assert(*full_region_prefix_end <= space->top(), "in-range");
}
return live_words;
}
bool ParallelCompactData::summarize(SplitInfo& split_info,
HeapWord* source_beg, HeapWord* source_end,
HeapWord** source_next,
HeapWord* target_beg, HeapWord* target_end,
HeapWord** target_next)
{
HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
log_develop_trace(gc, compaction)(
"sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
"tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
p2i(source_beg), p2i(source_end), p2i(source_next_val),
p2i(target_beg), p2i(target_end), p2i(*target_next));
size_t cur_region = addr_to_region_idx(source_beg);
const size_t end_region = addr_to_region_idx(region_align_up(source_end));
HeapWord *dest_addr = target_beg;
for (/* empty */; cur_region < end_region; cur_region++) {
size_t words = _region_data[cur_region].data_size();
// Skip empty ones
if (words == 0) {
continue;
}
if (split_info.is_split(cur_region)) {
assert(words > split_info.preceding_live_words(), "inv");
words -= split_info.preceding_live_words();
}
_region_data[cur_region].set_destination(dest_addr);
// If cur_region does not fit entirely into the target space, find a point
// at which the source space can be 'split' so that part is copied to the
// target space and the rest is copied elsewhere.
if (dest_addr + words > target_end) {
assert(source_next != nullptr, "source_next is null when splitting");
*source_next = summarize_split_space(cur_region, split_info, dest_addr,
target_end, target_next);
return false;
}
uint destination_count = split_info.is_split(cur_region)
? split_info.preceding_destination_count()
: 0;
HeapWord* const last_addr = dest_addr + words - 1;
const size_t dest_region_1 = addr_to_region_idx(dest_addr);
const size_t dest_region_2 = addr_to_region_idx(last_addr);
// Initially assume that the destination regions will be the same and
// adjust the value below if necessary. Under this assumption, if
// cur_region == dest_region_2, then cur_region will be compacted
// completely into itself.
destination_count += cur_region == dest_region_2 ? 0 : 1;
if (dest_region_1 != dest_region_2) {
// Destination regions differ; adjust destination_count.
destination_count += 1;
// Data from cur_region will be copied to the start of dest_region_2.
_region_data[dest_region_2].set_source_region(cur_region);
} else if (is_region_aligned(dest_addr)) {
// Data from cur_region will be copied to the start of the destination
// region.
_region_data[dest_region_1].set_source_region(cur_region);
}
_region_data[cur_region].set_destination_count(destination_count);
dest_addr += words;
}
*target_next = dest_addr;
return true;
}
#ifdef ASSERT
void ParallelCompactData::verify_clear() {
for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
if (!region(cur_idx)->is_clear()) {
log_warning(gc)("Uncleared Region: %u", cur_idx);
region(cur_idx)->verify_clear();
}
}
}
#endif // #ifdef ASSERT
STWGCTimer PSParallelCompact::_gc_timer;
ParallelOldTracer PSParallelCompact::_gc_tracer;
elapsedTimer PSParallelCompact::_accumulated_time;
unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
CollectorCounters* PSParallelCompact::_counters = nullptr;
ParMarkBitMap PSParallelCompact::_mark_bitmap;
ParallelCompactData PSParallelCompact::_summary_data;
PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
class PCAdjustPointerClosure: public BasicOopIterateClosure {
template <typename T>
void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
public:
virtual void do_oop(oop* p) { do_oop_work(p); }
virtual void do_oop(narrowOop* p) { do_oop_work(p); }
virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
};
static PCAdjustPointerClosure pc_adjust_pointer_closure;
bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
void PSParallelCompact::post_initialize() {
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
_span_based_discoverer.set_span(heap->reserved_region());
_ref_processor =
new ReferenceProcessor(&_span_based_discoverer,
ParallelGCThreads, // mt processing degree
ParallelGCThreads, // mt discovery degree
false, // concurrent_discovery
&_is_alive_closure); // non-header is alive closure
_counters = new CollectorCounters("Parallel full collection pauses", 1);
// Initialize static fields in ParCompactionManager.
ParCompactionManager::initialize(mark_bitmap());
}
bool PSParallelCompact::initialize_aux_data() {
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
MemRegion mr = heap->reserved_region();
assert(mr.byte_size() != 0, "heap should be reserved");
initialize_space_info();
if (!_mark_bitmap.initialize(mr)) {
vm_shutdown_during_initialization(
err_msg("Unable to allocate %zuKB bitmaps for parallel "
"garbage collection for the requested %zuKB heap.",
_mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
return false;
}
if (!_summary_data.initialize(mr)) {
vm_shutdown_during_initialization(
err_msg("Unable to allocate %zuKB card tables for parallel "
"garbage collection for the requested %zuKB heap.",
_summary_data.reserved_byte_size()/K, mr.byte_size()/K));
return false;
}
return true;
}
void PSParallelCompact::initialize_space_info()
{
memset(&_space_info, 0, sizeof(_space_info));
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
PSYoungGen* young_gen = heap->young_gen();
_space_info[old_space_id].set_space(heap->old_gen()->object_space());
_space_info[eden_space_id].set_space(young_gen->eden_space());
_space_info[from_space_id].set_space(young_gen->from_space());
_space_info[to_space_id].set_space(young_gen->to_space());
_space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
}
void
PSParallelCompact::clear_data_covering_space(SpaceId id)
{
// At this point, top is the value before GC, new_top() is the value that will
// be set at the end of GC. The marking bitmap is cleared to top; nothing
// should be marked above top. The summary data is cleared to the larger of
// top & new_top.
MutableSpace* const space = _space_info[id].space();
HeapWord* const bot = space->bottom();
HeapWord* const top = space->top();
HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
_mark_bitmap.clear_range(bot, top);
const size_t beg_region = _summary_data.addr_to_region_idx(bot);
const size_t end_region =
_summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
_summary_data.clear_range(beg_region, end_region);
// Clear the data used to 'split' regions.
SplitInfo& split_info = _space_info[id].split_info();
if (split_info.is_valid()) {
split_info.clear();
}
DEBUG_ONLY(split_info.verify_clear();)
}
void PSParallelCompact::pre_compact()
{
// Update the from & to space pointers in space_info, since they are swapped
// at each young gen gc. Do the update unconditionally (even though a
// promotion failure does not swap spaces) because an unknown number of young
// collections will have swapped the spaces an unknown number of times.
GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
_space_info[from_space_id].set_space(heap->young_gen()->from_space());
_space_info[to_space_id].set_space(heap->young_gen()->to_space());
// Increment the invocation count
heap->increment_total_collections(true);
CodeCache::on_gc_marking_cycle_start();
heap->print_before_gc();
heap->trace_heap_before_gc(&_gc_tracer);
// Fill in TLABs
heap->ensure_parsability(true); // retire TLABs
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
Universe::verify("Before GC");
}
DEBUG_ONLY(mark_bitmap()->verify_clear();)
DEBUG_ONLY(summary_data().verify_clear();)
}
void PSParallelCompact::post_compact()
{
GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
ParCompactionManager::remove_all_shadow_regions();
CodeCache::on_gc_marking_cycle_finish();
CodeCache::arm_all_nmethods();
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
// Clear the marking bitmap, summary data and split info.
clear_data_covering_space(SpaceId(id));
{
MutableSpace* space = _space_info[id].space();
HeapWord* top = space->top();
HeapWord* new_top = _space_info[id].new_top();
if (ZapUnusedHeapArea && new_top < top) {
space->mangle_region(MemRegion(new_top, top));
}
// Update top(). Must be done after clearing the bitmap and summary data.
space->set_top(new_top);
}
}
#ifdef ASSERT
{
mark_bitmap()->verify_clear();
summary_data().verify_clear();
}
#endif
ParCompactionManager::flush_all_string_dedup_requests();
MutableSpace* const eden_space = _space_info[eden_space_id].space();
MutableSpace* const from_space = _space_info[from_space_id].space();
MutableSpace* const to_space = _space_info[to_space_id].space();
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
bool eden_empty = eden_space->is_empty();
// Update heap occupancy information which is used as input to the soft ref
// clearing policy at the next gc.
Universe::heap()->update_capacity_and_used_at_gc();
bool young_gen_empty = eden_empty && from_space->is_empty() &&
to_space->is_empty();
PSCardTable* ct = heap->card_table();
MemRegion old_mr = heap->old_gen()->committed();
if (young_gen_empty) {
ct->clear_MemRegion(old_mr);
} else {
ct->dirty_MemRegion(old_mr);
}
{
// Delete metaspaces for unloaded class loaders and clean up loader_data graph
GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
ClassLoaderDataGraph::purge(true /* at_safepoint */);
DEBUG_ONLY(MetaspaceUtils::verify();)
}
// Need to clear claim bits for the next mark.
ClassLoaderDataGraph::clear_claimed_marks();
heap->prune_scavengable_nmethods();
#if COMPILER2_OR_JVMCI
DerivedPointerTable::update_pointers();
#endif
// Signal that we have completed a visit to all live objects.
Universe::heap()->record_whole_heap_examined_timestamp();
}
HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
HeapWord* full_region_prefix_end) {
const size_t region_size = ParallelCompactData::RegionSize;
const ParallelCompactData& sd = summary_data();
// Iteration starts with the region *after* the full-region-prefix-end.
const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
// If final region is not full, iteration stops before that region,
// because fill_dense_prefix_end assumes that prefix_end <= top.
const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
assert(start_region <= end_region, "inv");
size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
const RegionData* cur_region = start_region;
for (/* empty */; cur_region < end_region; ++cur_region) {
assert(region_size >= cur_region->data_size(), "inv");
size_t dead_size = region_size - cur_region->data_size();
if (max_waste < dead_size) {
break;
}
max_waste -= dead_size;
}
HeapWord* const prefix_end = sd.region_to_addr(cur_region);
assert(sd.is_region_aligned(prefix_end), "postcondition");
assert(prefix_end >= full_region_prefix_end, "in-range");
assert(prefix_end <= old_space->top(), "in-range");
return prefix_end;
}
void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
// Comparing two sizes to decide if filling is required:
//
// The size of the filler (min-obj-size) is 2 heap words with the default
// MinObjAlignment, since both markword and klass take 1 heap word.
// With +UseCompactObjectHeaders, the minimum filler size is only one word,
// because the Klass* gets encoded in the mark-word.
//
// The size of the gap (if any) right before dense-prefix-end is
// MinObjAlignment.
//
// Need to fill in the gap only if it's smaller than min-obj-size, and the
// filler obj will extend to next region.
if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
return;
}
assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
assert(CollectedHeap::min_fill_size() == 2, "inv");
HeapWord* const dense_prefix_end = dense_prefix(id);
assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
assert(dense_prefix_end <= space(id)->top(), "precondition");
if (dense_prefix_end == space(id)->top()) {
// Must not have single-word gap right before prefix-end/top.
return;
}
RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
if (region_after_dense_prefix->partial_obj_size() != 0 ||
_mark_bitmap.is_marked(dense_prefix_end)) {
// The region after the dense prefix starts with live bytes.
return;
}
HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
if (block_start == dense_prefix_end - 1) {
assert(!_mark_bitmap.is_marked(block_start), "inv");
// There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
// The filler object will extend into region_after_dense_prefix.
const size_t obj_len = 2; // min-fill-size
HeapWord* const obj_beg = dense_prefix_end - 1;
CollectedHeap::fill_with_object(obj_beg, obj_len);
_mark_bitmap.mark_obj(obj_beg);
_summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
region_after_dense_prefix->set_partial_obj_size(1);
region_after_dense_prefix->set_partial_obj_addr(obj_beg);
assert(start_array(id) != nullptr, "sanity");
start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
}
}
bool PSParallelCompact::check_maximum_compaction(size_t total_live_words,
MutableSpace* const old_space,
HeapWord* full_region_prefix_end) {
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
// Check System.GC
bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
&& GCCause::is_user_requested_gc(heap->gc_cause());
// Check if all live objs are larger than old-gen.
const bool is_old_gen_overflowing = (total_live_words > old_space->capacity_in_words());
// JVM flags
const uint total_invocations = heap->total_full_collections();
assert(total_invocations >= _maximum_compaction_gc_num, "sanity");
const size_t gcs_since_max = total_invocations - _maximum_compaction_gc_num;
const bool is_interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
// If all regions in old-gen are full
const bool is_region_full =
full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
if (is_max_on_system_gc || is_old_gen_overflowing || is_interval_ended || is_region_full) {
_maximum_compaction_gc_num = total_invocations;
return true;
}
return false;
}
void PSParallelCompact::summary_phase()
{
GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
MutableSpace* const old_space = _space_info[old_space_id].space();
{
size_t total_live_words = 0;
HeapWord* full_region_prefix_end = nullptr;
{
// old-gen
size_t live_words = _summary_data.live_words_in_space(old_space,
&full_region_prefix_end);
total_live_words += live_words;
}
// young-gen
for (uint i = eden_space_id; i < last_space_id; ++i) {
const MutableSpace* space = _space_info[i].space();
size_t live_words = _summary_data.live_words_in_space(space);
total_live_words += live_words;
_space_info[i].set_new_top(space->bottom() + live_words);
_space_info[i].set_dense_prefix(space->bottom());
}
bool maximum_compaction = check_maximum_compaction(total_live_words,
old_space,
full_region_prefix_end);
HeapWord* dense_prefix_end = maximum_compaction
? full_region_prefix_end
: compute_dense_prefix_for_old_space(old_space,
full_region_prefix_end);
SpaceId id = old_space_id;
_space_info[id].set_dense_prefix(dense_prefix_end);
if (dense_prefix_end != old_space->bottom()) {
fill_dense_prefix_end(id);
_summary_data.summarize_dense_prefix(old_space->bottom(), dense_prefix_end);
}
// Compacting objs in [dense_prefix_end, old_space->top())
_summary_data.summarize(_space_info[id].split_info(),
dense_prefix_end, old_space->top(), nullptr,
dense_prefix_end, old_space->end(),
_space_info[id].new_top_addr());
}
// Summarize the remaining spaces in the young gen. The initial target space
// is the old gen. If a space does not fit entirely into the target, then the
// remainder is compacted into the space itself and that space becomes the new
// target.
SpaceId dst_space_id = old_space_id;
HeapWord* dst_space_end = old_space->end();
HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
const MutableSpace* space = _space_info[id].space();
const size_t live = pointer_delta(_space_info[id].new_top(),
space->bottom());
const size_t available = pointer_delta(dst_space_end, *new_top_addr);
if (live > 0 && live <= available) {
// All the live data will fit.
bool done = _summary_data.summarize(_space_info[id].split_info(),
space->bottom(), space->top(),
nullptr,
*new_top_addr, dst_space_end,
new_top_addr);
assert(done, "space must fit into old gen");
// Reset the new_top value for the space.
_space_info[id].set_new_top(space->bottom());
} else if (live > 0) {
// Attempt to fit part of the source space into the target space.
HeapWord* next_src_addr = nullptr;
bool done = _summary_data.summarize(_space_info[id].split_info(),
space->bottom(), space->top(),
&next_src_addr,
*new_top_addr, dst_space_end,
new_top_addr);
assert(!done, "space should not fit into old gen");
assert(next_src_addr != nullptr, "sanity");
// The source space becomes the new target, so the remainder is compacted
// within the space itself.
dst_space_id = SpaceId(id);
dst_space_end = space->end();
new_top_addr = _space_info[id].new_top_addr();
done = _summary_data.summarize(_space_info[id].split_info(),
next_src_addr, space->top(),
nullptr,
space->bottom(), dst_space_end,
new_top_addr);
assert(done, "space must fit when compacted into itself");
assert(*new_top_addr <= space->top(), "usage should not grow");
}
}
}
// This method should contain all heap-specific policy for invoking a full
// collection. invoke_no_policy() will only attempt to compact the heap; it
// will do nothing further. If we need to bail out for policy reasons, scavenge
// before full gc, or any other specialized behavior, it needs to be added here.
//
// Note that this method should only be called from the vm_thread while at a
// safepoint.
//
// Note that the all_soft_refs_clear flag in the soft ref policy
// may be true because this method can be called without intervening
// activity. For example when the heap space is tight and full measure
// are being taken to free space.
bool PSParallelCompact::invoke(bool clear_all_soft_refs) {
assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
assert(Thread::current() == (Thread*)VMThread::vm_thread(),
"should be in vm thread");
SvcGCMarker sgcm(SvcGCMarker::FULL);
IsSTWGCActiveMark mark;
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
clear_all_soft_refs = clear_all_soft_refs
|| heap->soft_ref_policy()->should_clear_all_soft_refs();
return PSParallelCompact::invoke_no_policy(clear_all_soft_refs);
}
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSParallelCompact::invoke_no_policy(bool clear_all_soft_refs) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
assert(ref_processor() != nullptr, "Sanity");
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
GCIdMark gc_id_mark;
_gc_timer.register_gc_start();
_gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
GCCause::Cause gc_cause = heap->gc_cause();
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSAdaptiveSizePolicy* size_policy = heap->size_policy();
// The scope of casr should end after code that can change
// SoftRefPolicy::_should_clear_all_soft_refs.
ClearedAllSoftRefs casr(clear_all_soft_refs,
heap->soft_ref_policy());
// Make sure data structures are sane, make the heap parsable, and do other
// miscellaneous bookkeeping.
pre_compact();
const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
{
const uint active_workers =
WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
ParallelScavengeHeap::heap()->workers().active_workers(),
Threads::number_of_non_daemon_threads());
ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
GCTraceCPUTime tcpu(&_gc_tracer);
GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
heap->pre_full_gc_dump(&_gc_timer);
TraceCollectorStats tcs(counters());
TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
if (log_is_enabled(Debug, gc, heap, exit)) {
accumulated_time()->start();
}
// Let the size policy know we're starting
size_policy->major_collection_begin();
#if COMPILER2_OR_JVMCI
DerivedPointerTable::clear();
#endif
ref_processor()->start_discovery(clear_all_soft_refs);
ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
false /* unregister_nmethods_during_purge */,
false /* lock_nmethod_free_separately */);
marking_phase(&_gc_tracer);
summary_phase();
#if COMPILER2_OR_JVMCI
assert(DerivedPointerTable::is_active(), "Sanity");
DerivedPointerTable::set_active(false);
#endif
forward_to_new_addr();
adjust_pointers();
compact();
ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
ParCompactionManager::verify_all_region_stack_empty();
// Reset the mark bitmap, summary data, and do other bookkeeping. Must be
// done before resizing.
post_compact();
// Let the size policy know we're done
size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
if (UseAdaptiveSizePolicy) {
log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
log_trace(gc, ergo)("old_gen_capacity: %zu young_gen_capacity: %zu",
old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
// Don't check if the size_policy is ready here. Let
// the size_policy check that internally.
if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
// Swap the survivor spaces if from_space is empty. The
// resize_young_gen() called below is normally used after
// a successful young GC and swapping of survivor spaces;
// otherwise, it will fail to resize the young gen with
// the current implementation.
if (young_gen->from_space()->is_empty()) {
young_gen->from_space()->clear(SpaceDecorator::Mangle);
young_gen->swap_spaces();
}
// Calculate optimal free space amounts
assert(young_gen->max_gen_size() >
young_gen->from_space()->capacity_in_bytes() +
young_gen->to_space()->capacity_in_bytes(),
"Sizes of space in young gen are out-of-bounds");
size_t young_live = young_gen->used_in_bytes();
size_t eden_live = young_gen->eden_space()->used_in_bytes();
size_t old_live = old_gen->used_in_bytes();
size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
size_t max_old_gen_size = old_gen->max_gen_size();
size_t max_eden_size = young_gen->max_gen_size() -
young_gen->from_space()->capacity_in_bytes() -
young_gen->to_space()->capacity_in_bytes();
// Used for diagnostics
size_policy->clear_generation_free_space_flags();
size_policy->compute_generations_free_space(young_live,
eden_live,
old_live,
cur_eden,
max_old_gen_size,
max_eden_size,
true /* full gc*/);
size_policy->check_gc_overhead_limit(eden_live,
max_old_gen_size,
max_eden_size,
true /* full gc*/,
gc_cause,
heap->soft_ref_policy());
size_policy->decay_supplemental_growth(true /* full gc*/);
heap->resize_old_gen(
size_policy->calculated_old_free_size_in_bytes());
heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
size_policy->calculated_survivor_size_in_bytes());
}
log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
}
if (UsePerfData) {
PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
counters->update_counters();
counters->update_old_capacity(old_gen->capacity_in_bytes());
counters->update_young_capacity(young_gen->capacity_in_bytes());
}
heap->resize_all_tlabs();
// Resize the metaspace capacity after a collection
MetaspaceGC::compute_new_size();
if (log_is_enabled(Debug, gc, heap, exit)) {
accumulated_time()->stop();
}
heap->print_heap_change(pre_gc_values);
// Track memory usage and detect low memory
MemoryService::track_memory_usage();
heap->update_counters();
heap->post_full_gc_dump(&_gc_timer);
}
if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
Universe::verify("After GC");
}
heap->print_after_gc();
heap->trace_heap_after_gc(&_gc_tracer);
AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
_gc_timer.register_gc_end();
_gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
_gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
return true;
}
class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
private:
uint _worker_id;
public:
PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
void do_thread(Thread* thread) {
assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
ResourceMark rm;
ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
MarkingNMethodClosure mark_and_push_in_blobs(&cm->_mark_and_push_closure,
!NMethodToOopClosure::FixRelocations,
true /* keepalive nmethods */);
thread->oops_do(&cm->_mark_and_push_closure, &mark_and_push_in_blobs);
// Do the real work
cm->follow_marking_stacks();
}
};
void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
ParCompactionManager* cm =
ParCompactionManager::gc_thread_compaction_manager(worker_id);
do {
ScannerTask task;
if (ParCompactionManager::steal(worker_id, task)) {
cm->follow_contents(task, true);
}
cm->follow_marking_stacks();
} while (!terminator.offer_termination());
}
class MarkFromRootsTask : public WorkerTask {
StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
TaskTerminator _terminator;
uint _active_workers;
public:
MarkFromRootsTask(uint active_workers) :
WorkerTask("MarkFromRootsTask"),
_strong_roots_scope(active_workers),
_terminator(active_workers, ParCompactionManager::marking_stacks()),
_active_workers(active_workers) {}
virtual void work(uint worker_id) {
ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
cm->create_marking_stats_cache();
{
CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
// Do the real work
cm->follow_marking_stacks();
}
{
PCAddThreadRootsMarkingTaskClosure closure(worker_id);
Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
}
// Mark from OopStorages
{
_oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
// Do the real work
cm->follow_marking_stacks();
}
if (_active_workers > 1) {
steal_marking_work(_terminator, worker_id);
}
}
};
class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
TaskTerminator _terminator;
public:
ParallelCompactRefProcProxyTask(uint max_workers)
: RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
_terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
void work(uint worker_id) override {
assert(worker_id < _max_workers, "sanity");
ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
BarrierEnqueueDiscoveredFieldClosure enqueue;
ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
_rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
}
void prepare_run_task_hook() override {
_terminator.reset_for_reuse(_queue_count);
}
};
static void flush_marking_stats_cache(const uint num_workers) {
for (uint i = 0; i < num_workers; ++i) {
ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
cm->flush_and_destroy_marking_stats_cache();
}
}
void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
// Recursively traverse all live objects and mark them
GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
{
GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
MarkFromRootsTask task(active_gc_threads);
ParallelScavengeHeap::heap()->workers().run_task(&task);
}
// Process reference objects found during marking
{
GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
ReferenceProcessorStats stats;
ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
ref_processor()->set_active_mt_degree(active_gc_threads);
ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
stats = ref_processor()->process_discovered_references(task, pt);
gc_tracer->report_gc_reference_stats(stats);
pt.print_all_references();
}
{
GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
flush_marking_stats_cache(active_gc_threads);
}
// This is the point where the entire marking should have completed.
ParCompactionManager::verify_all_marking_stack_empty();
{
GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
is_alive_closure(),
&do_nothing_cl,
1);
}
{
GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
ClassUnloadingContext* ctx = ClassUnloadingContext::context();
bool unloading_occurred;
{
CodeCache::UnlinkingScope scope(is_alive_closure());
// Follow system dictionary roots and unload classes.
unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
// Unload nmethods.
CodeCache::do_unloading(unloading_occurred);
}
{
GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
// Release unloaded nmethod's memory.
ctx->purge_nmethods();
}
{
GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
}
{
GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
ctx->free_nmethods();
}
// Prune dead klasses from subklass/sibling/implementor lists.
Klass::clean_weak_klass_links(unloading_occurred);
// Clean JVMCI metadata handles.
JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
}
{
GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
_gc_tracer.report_object_count_after_gc(is_alive_closure(), &ParallelScavengeHeap::heap()->workers());
}
#if TASKQUEUE_STATS
ParCompactionManager::print_and_reset_taskqueue_stats();
#endif
}
template<typename Func>
void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
MutableSpace* sp = PSParallelCompact::space(id);
HeapWord* const bottom = sp->bottom();
HeapWord* const top = sp->top();
if (bottom == top) {
return;
}
const uint num_regions_per_stripe = 2;
const size_t region_size = ParallelCompactData::RegionSize;
const size_t stripe_size = num_regions_per_stripe * region_size;
while (true) {
uint counter = Atomic::fetch_then_add(claim_counter, num_regions_per_stripe);
HeapWord* cur_stripe = bottom + counter * region_size;
if (cur_stripe >= top) {
break;
}
HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
on_stripe(cur_stripe, stripe_end);
}
}
void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
// Regions in old-space shouldn't be split.
assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
assert(mark_bitmap()->is_marked(obj_start), "inv");
oop obj = cast_to_oop(obj_start);
return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
};
adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
assert(_summary_data.is_region_aligned(stripe_start), "inv");
RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
HeapWord* obj_start;
if (cur_region->partial_obj_size() != 0) {
obj_start = cur_region->partial_obj_addr();
obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
} else {
obj_start = stripe_start;
}
while (obj_start < stripe_end) {
obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
if (obj_start >= stripe_end) {
break;
}
obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
}
});
}
void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
HeapWord* obj_start = stripe_start;
while (obj_start < stripe_end) {
obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
if (obj_start >= stripe_end) {
break;
}
oop obj = cast_to_oop(obj_start);
obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
}
});
}
void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
auto start_time = Ticks::now();
adjust_in_old_space(&claim_counters[0]);
for (uint id = eden_space_id; id < last_space_id; ++id) {
adjust_in_young_space(SpaceId(id), &claim_counters[id]);
}
log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
}
class PSAdjustTask final : public WorkerTask {
SubTasksDone _sub_tasks;
WeakProcessor::Task _weak_proc_task;
OopStorageSetStrongParState<false, false> _oop_storage_iter;
uint _nworkers;
volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
enum PSAdjustSubTask {
PSAdjustSubTask_code_cache,
PSAdjustSubTask_num_elements
};
public:
PSAdjustTask(uint nworkers) :
WorkerTask("PSAdjust task"),
_sub_tasks(PSAdjustSubTask_num_elements),
_weak_proc_task(nworkers),
_nworkers(nworkers) {
ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
if (nworkers > 1) {
Threads::change_thread_claim_token();
}
}
~PSAdjustTask() {
Threads::assert_all_threads_claimed();
}
void work(uint worker_id) {
ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
cm->preserved_marks()->adjust_during_full_gc();
{
// adjust pointers in all spaces
PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
}
{
ResourceMark rm;
Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
}
_oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
{
CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
ClassLoaderDataGraph::cld_do(&cld_closure);
}
{
AlwaysTrueClosure always_alive;
_weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
}
if (_sub_tasks.try_claim_task(PSAdjustSubTask_code_cache)) {
NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
CodeCache::nmethods_do(&adjust_code);
}
_sub_tasks.all_tasks_claimed();
}
};
void PSParallelCompact::adjust_pointers() {
// Adjust the pointers to reflect the new locations
GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
PSAdjustTask task(nworkers);
ParallelScavengeHeap::heap()->workers().run_task(&task);
}
// Split [start, end) evenly for a number of workers and return the
// range for worker_id.
static void split_regions_for_worker(size_t start, size_t end,
uint worker_id, uint num_workers,
size_t* worker_start, size_t* worker_end) {
assert(start < end, "precondition");
assert(num_workers > 0, "precondition");
assert(worker_id < num_workers, "precondition");
size_t num_regions = end - start;
size_t num_regions_per_worker = num_regions / num_workers;
size_t remainder = num_regions % num_workers;
// The first few workers will get one extra.
*worker_start = start + worker_id * num_regions_per_worker
+ MIN2(checked_cast<size_t>(worker_id), remainder);
*worker_end = *worker_start + num_regions_per_worker
+ (worker_id < remainder ? 1 : 0);
}
void PSParallelCompact::forward_to_new_addr() {
GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
struct ForwardTask final : public WorkerTask {
uint _num_workers;
explicit ForwardTask(uint num_workers) :
WorkerTask("PSForward task"),
_num_workers(num_workers) {}
static void forward_objs_in_range(ParCompactionManager* cm,
HeapWord* start,
HeapWord* end,
HeapWord* destination) {
HeapWord* cur_addr = start;
HeapWord* new_addr = destination;
while (cur_addr < end) {
cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
if (cur_addr >= end) {
return;
}
assert(mark_bitmap()->is_marked(cur_addr), "inv");
oop obj = cast_to_oop(cur_addr);
if (new_addr != cur_addr) {
cm->preserved_marks()->push_if_necessary(obj, obj->mark());
FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
}
size_t obj_size = obj->size();
new_addr += obj_size;
cur_addr += obj_size;
}
}
void work(uint worker_id) override {
ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
for (uint id = old_space_id; id < last_space_id; ++id) {
MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
HeapWord* top = sp->top();
if (dense_prefix_addr == top) {
continue;
}
const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
size_t start_region;
size_t end_region;
split_regions_for_worker(dense_prefix_region, top_region,
worker_id, _num_workers,
&start_region, &end_region);
for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
RegionData* region_ptr = _summary_data.region(cur_region);
size_t partial_obj_size = region_ptr->partial_obj_size();
if (partial_obj_size == ParallelCompactData::RegionSize) {
// No obj-start
continue;
}
HeapWord* region_start = _summary_data.region_to_addr(cur_region);
HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
if (split_info.is_split(cur_region)) {
// Part 1: will be relocated to space-1
HeapWord* preceding_destination = split_info.preceding_destination();
HeapWord* split_point = split_info.split_point();
forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
// Part 2: will be relocated to space-2
HeapWord* destination = region_ptr->destination();
forward_objs_in_range(cm, split_point, region_end, destination);
} else {
HeapWord* destination = region_ptr->destination();
forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
}
}
}
}
} task(nworkers);
ParallelScavengeHeap::heap()->workers().run_task(&task);
DEBUG_ONLY(verify_forward();)
}
#ifdef ASSERT
void PSParallelCompact::verify_forward() {
HeapWord* old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
RegionData* old_region = _summary_data.region(_summary_data.addr_to_region_idx(old_dense_prefix_addr));
HeapWord* bump_ptr = old_region->partial_obj_size() != 0
? old_dense_prefix_addr + old_region->partial_obj_size()
: old_dense_prefix_addr;
SpaceId bump_ptr_space = old_space_id;
for (uint id = old_space_id; id < last_space_id; ++id) {
MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
HeapWord* top = sp->top();
HeapWord* cur_addr = dense_prefix_addr;
while (cur_addr < top) {
cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
if (cur_addr >= top) {
break;
}
assert(mark_bitmap()->is_marked(cur_addr), "inv");
assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
// Move to the space containing cur_addr
if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
bump_ptr = space(space_id(cur_addr))->bottom();
bump_ptr_space = space_id(bump_ptr);
}
oop obj = cast_to_oop(cur_addr);
if (cur_addr == bump_ptr) {
assert(!FullGCForwarding::is_forwarded(obj), "inv");
} else {
assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
}
bump_ptr += obj->size();
cur_addr += obj->size();
}
}
}
#endif
// Helper class to print 8 region numbers per line and then print the total at the end.
class FillableRegionLogger : public StackObj {
private:
Log(gc, compaction) log;
static const int LineLength = 8;
size_t _regions[LineLength];
int _next_index;
bool _enabled;
size_t _total_regions;
public:
FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
~FillableRegionLogger() {
log.trace("%zu initially fillable regions", _total_regions);
}
void print_line() {
if (!_enabled || _next_index == 0) {
return;
}
FormatBuffer<> line("Fillable: ");
for (int i = 0; i < _next_index; i++) {
line.append(" %7zu", _regions[i]);
}
log.trace("%s", line.buffer());
_next_index = 0;
}
void handle(size_t region) {
if (!_enabled) {
return;
}
_regions[_next_index++] = region;
if (_next_index == LineLength) {
print_line();
}
_total_regions++;
}
};
void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
{
GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
// Find the threads that are active
uint worker_id = 0;
// Find all regions that are available (can be filled immediately) and
// distribute them to the thread stacks. The iteration is done in reverse
// order (high to low) so the regions will be removed in ascending order.
const ParallelCompactData& sd = PSParallelCompact::summary_data();
// id + 1 is used to test termination so unsigned can
// be used with an old_space_id == 0.
FillableRegionLogger region_logger;
for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
SpaceInfo* const space_info = _space_info + id;
HeapWord* const new_top = space_info->new_top();
const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
const size_t end_region =
sd.addr_to_region_idx(sd.region_align_up(new_top));
for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
if (sd.region(cur)->claim_unsafe()) {
ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
bool result = sd.region(cur)->mark_normal();
assert(result, "Must succeed at this point.");
cm->region_stack()->push(cur);
region_logger.handle(cur);
// Assign regions to tasks in round-robin fashion.
if (++worker_id == parallel_gc_threads) {
worker_id = 0;
}
}
}
region_logger.print_line();
}
}
static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
ParCompactionManager* cm =
ParCompactionManager::gc_thread_compaction_manager(worker_id);
// Drain the stacks that have been preloaded with regions
// that are ready to fill.
cm->drain_region_stacks();
guarantee(cm->region_stack()->is_empty(), "Not empty");
size_t region_index = 0;
while (true) {
if (ParCompactionManager::steal(worker_id, region_index)) {
PSParallelCompact::fill_and_update_region(cm, region_index);
cm->drain_region_stacks();
} else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
// Fill and update an unavailable region with the help of a shadow region
PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
cm->drain_region_stacks();
} else {
if (terminator->offer_termination()) {
break;
}
// Go around again.
}
}
}
class FillDensePrefixAndCompactionTask: public WorkerTask {
uint _num_workers;
TaskTerminator _terminator;
public:
FillDensePrefixAndCompactionTask(uint active_workers) :
WorkerTask("FillDensePrefixAndCompactionTask"),
_num_workers(active_workers),
_terminator(active_workers, ParCompactionManager::region_task_queues()) {
}
virtual void work(uint worker_id) {
{
auto start = Ticks::now();
PSParallelCompact::fill_dead_objs_in_dense_prefix(worker_id, _num_workers);
log_trace(gc, phases)("Fill dense prefix by worker %u: %.3f ms", worker_id, (Ticks::now() - start).seconds() * 1000);
}
compaction_with_stealing_work(&_terminator, worker_id);
}
};
void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
#ifdef ASSERT
{
assert(start < end, "precondition");
assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
HeapWord* bottom = _space_info[old_space_id].space()->bottom();
if (start != bottom) {
HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
HeapWord* after_obj = obj_start + cast_to_oop(obj_start)->size();
assert(after_obj == start, "precondition");
}
}
#endif
CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
HeapWord* addr = start;
do {
size_t size = cast_to_oop(addr)->size();
start_array(old_space_id)->update_for_block(addr, addr + size);
addr += size;
} while (addr < end);
}
void PSParallelCompact::fill_dead_objs_in_dense_prefix(uint worker_id, uint num_workers) {
ParMarkBitMap* bitmap = mark_bitmap();
HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
HeapWord* const prefix_end = dense_prefix(old_space_id);
if (bottom == prefix_end) {
return;
}
size_t bottom_region = _summary_data.addr_to_region_idx(bottom);
size_t prefix_end_region = _summary_data.addr_to_region_idx(prefix_end);
size_t start_region;
size_t end_region;
split_regions_for_worker(bottom_region, prefix_end_region,
worker_id, num_workers,
&start_region, &end_region);
if (start_region == end_region) {
return;
}
HeapWord* const start_addr = _summary_data.region_to_addr(start_region);
HeapWord* const end_addr = _summary_data.region_to_addr(end_region);
// Skip live partial obj (if any) from previous region.
HeapWord* cur_addr;
RegionData* start_region_ptr = _summary_data.region(start_region);
if (start_region_ptr->partial_obj_size() != 0) {
HeapWord* partial_obj_start = start_region_ptr->partial_obj_addr();
assert(bitmap->is_marked(partial_obj_start), "inv");
cur_addr = partial_obj_start + cast_to_oop(partial_obj_start)->size();
} else {
cur_addr = start_addr;
}
// end_addr is inclusive to handle regions starting with dead space.
while (cur_addr <= end_addr) {
// Use prefix_end to handle trailing obj in each worker region-chunk.
HeapWord* live_start = bitmap->find_obj_beg(cur_addr, prefix_end);
if (cur_addr != live_start) {
// Only worker 0 handles proceeding dead space.
if (cur_addr != start_addr || worker_id == 0) {
fill_range_in_dense_prefix(cur_addr, live_start);
}
}
if (live_start >= end_addr) {
break;
}
assert(bitmap->is_marked(live_start), "inv");
cur_addr = live_start + cast_to_oop(live_start)->size();
}
}
void PSParallelCompact::compact() {
GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
initialize_shadow_regions(active_gc_threads);
prepare_region_draining_tasks(active_gc_threads);
{
GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
FillDensePrefixAndCompactionTask task(active_gc_threads);
ParallelScavengeHeap::heap()->workers().run_task(&task);
#ifdef ASSERT
verify_filler_in_dense_prefix();
// Verify that all regions have been processed.
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
verify_complete(SpaceId(id));
}
#endif
}
}
#ifdef ASSERT
void PSParallelCompact::verify_filler_in_dense_prefix() {
HeapWord* bottom = _space_info[old_space_id].space()->bottom();
HeapWord* dense_prefix_end = dense_prefix(old_space_id);
HeapWord* cur_addr = bottom;
while (cur_addr < dense_prefix_end) {
oop obj = cast_to_oop(cur_addr);
oopDesc::verify(obj);
if (!mark_bitmap()->is_marked(cur_addr)) {
Klass* k = cast_to_oop(cur_addr)->klass();
assert(k == Universe::fillerArrayKlass() || k == vmClasses::FillerObject_klass(), "inv");
}
cur_addr += obj->size();
}
}
void PSParallelCompact::verify_complete(SpaceId space_id) {
// All Regions served as compaction targets, from dense_prefix() to
// new_top(), should be marked as filled and all Regions between new_top()
// and top() should be available (i.e., should have been emptied).
ParallelCompactData& sd = summary_data();
SpaceInfo si = _space_info[space_id];
HeapWord* new_top_addr = sd.region_align_up(si.new_top());
HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
size_t cur_region;
for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
const RegionData* const c = sd.region(cur_region);
assert(c->completed(), "region %zu not filled: destination_count=%u",
cur_region, c->destination_count());
}
for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
const RegionData* const c = sd.region(cur_region);
assert(c->available(), "region %zu not empty: destination_count=%u",
cur_region, c->destination_count());
}
}
#endif // #ifdef ASSERT
// Return the SpaceId for the space containing addr. If addr is not in the
// heap, last_space_id is returned. In debug mode it expects the address to be
// in the heap and asserts such.
PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
if (_space_info[id].space()->contains(addr)) {
return SpaceId(id);
}
}
assert(false, "no space contains the addr");
return last_space_id;
}
// Skip over count live words starting from beg, and return the address of the
// next live word. Callers must also ensure that there are enough live words in
// the range [beg, end) to skip.
HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
{
ParMarkBitMap* m = mark_bitmap();
HeapWord* cur_addr = beg;
while (true) {
cur_addr = m->find_obj_beg(cur_addr, end);
assert(cur_addr < end, "inv");
size_t obj_size = cast_to_oop(cur_addr)->size();
// Strictly greater-than
if (obj_size > count) {
return cur_addr + count;
}
count -= obj_size;
cur_addr += obj_size;
}
}
// On starting to fill a destination region (dest-region), we need to know the
// location of the word that will be at the start of the dest-region after
// compaction. A dest-region can have one or more source regions, but only the
// first source-region contains this location. This location is retrieved by
// calling `first_src_addr` on a dest-region.
// Conversely, a source-region has a dest-region which holds the destination of
// the first live word on this source-region, based on which the destination
// for the rest of live words can be derived.
//
// Note:
// There is some complication due to space-boundary-fragmentation (an obj can't
// cross space-boundary) -- a source-region may be split and behave like two
// distinct regions with their own dest-region, as depicted below.
//
// source-region: region-n
//
// **********************
// | A|A~~~~B|B |
// **********************
// n-1 n n+1
//
// AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
//
// Assuming the dest-region for region-n is the final region before
// old-space-end and its first-live-word is the middle of AA, the heap content
// will look like the following after compaction:
//
// ************** *************
// A|A~~~~ | |BB |
// ************** *************
// ^ ^
// | old-space-end | eden-space-start
//
// Therefore, in this example, region-n will have two dest-regions:
// 1. the final region in old-space
// 2. the first region in eden-space.
// To handle this special case, we introduce the concept of split-region, whose
// contents are relocated to two spaces. `SplitInfo` captures all necessary
// info about the split, the first part, spliting-point, and the second part.
HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
SpaceId src_space_id,
size_t src_region_idx)
{
const size_t RegionSize = ParallelCompactData::RegionSize;
const ParallelCompactData& sd = summary_data();
assert(sd.is_region_aligned(dest_addr), "precondition");
const RegionData* const src_region_ptr = sd.region(src_region_idx);
assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
const size_t partial_obj_size = src_region_ptr->partial_obj_size();
HeapWord* const src_region_destination = src_region_ptr->destination();
HeapWord* const region_start = sd.region_to_addr(src_region_idx);
HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
// Identify the actual destination for the first live words on this region,
// taking split-region into account.
HeapWord* region_start_destination;
const SplitInfo& split_info = _space_info[src_space_id].split_info();
if (split_info.is_split(src_region_idx)) {
// The second part of this split region; use the recorded split point.
if (dest_addr == src_region_destination) {
return split_info.split_point();
}
region_start_destination = split_info.preceding_destination();
} else {
region_start_destination = src_region_destination;
}
// Calculate the offset to be skipped
size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
HeapWord* result;
if (partial_obj_size > words_to_skip) {
result = region_start + words_to_skip;
} else {
words_to_skip -= partial_obj_size;
result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
}
if (split_info.is_split(src_region_idx)) {
assert(result < split_info.split_point(), "postcondition");
} else {
assert(result < region_end, "postcondition");
}
return result;
}
void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
SpaceId src_space_id,
size_t beg_region,
HeapWord* end_addr)
{
ParallelCompactData& sd = summary_data();
#ifdef ASSERT
MutableSpace* const src_space = _space_info[src_space_id].space();
HeapWord* const beg_addr = sd.region_to_addr(beg_region);
assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
"src_space_id does not match beg_addr");
assert(src_space->contains(end_addr) || end_addr == src_space->end(),
"src_space_id does not match end_addr");
#endif // #ifdef ASSERT
RegionData* const beg = sd.region(beg_region);
RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
// Regions up to new_top() are enqueued if they become available.
HeapWord* const new_top = _space_info[src_space_id].new_top();
RegionData* const enqueue_end =
sd.addr_to_region_ptr(sd.region_align_up(new_top));
for (RegionData* cur = beg; cur < end; ++cur) {
assert(cur->data_size() > 0, "region must have live data");
cur->decrement_destination_count();
if (cur < enqueue_end && cur->available() && cur->claim()) {
if (cur->mark_normal()) {
cm->push_region(sd.region(cur));
} else if (cur->mark_copied()) {
// Try to copy the content of the shadow region back to its corresponding
// heap region if the shadow region is filled. Otherwise, the GC thread
// fills the shadow region will copy the data back (see
// MoveAndUpdateShadowClosure::complete_region).
copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
cur->set_completed();
}
}
}
}
size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
SpaceId& src_space_id,
HeapWord*& src_space_top,
HeapWord* end_addr)
{
ParallelCompactData& sd = PSParallelCompact::summary_data();
size_t src_region_idx = 0;
// Skip empty regions (if any) up to the top of the space.
HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
++src_region_ptr;
}
if (src_region_ptr < top_region_ptr) {
// Found the first non-empty region in the same space.
src_region_idx = sd.region(src_region_ptr);
closure.set_source(sd.region_to_addr(src_region_idx));
return src_region_idx;
}
// Switch to a new source space and find the first non-empty region.
uint space_id = src_space_id + 1;
assert(space_id < last_space_id, "not enough spaces");
for (/* empty */; space_id < last_space_id; ++space_id) {
HeapWord* bottom = _space_info[space_id].space()->bottom();
HeapWord* top = _space_info[space_id].space()->top();
// Skip empty space
if (bottom == top) {
continue;
}
// Identify the first region that contains live words in this space
size_t cur_region = sd.addr_to_region_idx(bottom);
size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
for (/* empty */ ; cur_region < end_region; ++cur_region) {
RegionData* cur = sd.region(cur_region);
if (cur->live_obj_size() > 0) {
HeapWord* region_start_addr = sd.region_to_addr(cur_region);
src_space_id = SpaceId(space_id);
src_space_top = top;
closure.set_source(region_start_addr);
return cur_region;
}
}
}
ShouldNotReachHere();
}
HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
ParallelCompactData& sd = summary_data();
assert(sd.is_region_aligned(region_start_addr), "precondition");
// Use per-region partial_obj_size to locate the end of the obj, that extends
// to region_start_addr.
size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
size_t end_region_idx = sd.region_count();
size_t accumulated_size = 0;
for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
accumulated_size += cur_partial_obj_size;
if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
break;
}
}
return region_start_addr + accumulated_size;
}
// Use region_idx as the destination region, and evacuate all live objs on its
// source regions to this destination region.
void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
{
ParMarkBitMap* const bitmap = mark_bitmap();
ParallelCompactData& sd = summary_data();
RegionData* const region_ptr = sd.region(region_idx);
// Get the source region and related info.
size_t src_region_idx = region_ptr->source_region();
SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
HeapWord* src_space_top = _space_info[src_space_id].space()->top();
HeapWord* dest_addr = sd.region_to_addr(region_idx);
closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
// Adjust src_region_idx to prepare for decrementing destination counts (the
// destination count is not decremented when a region is copied to itself).
if (src_region_idx == region_idx) {
src_region_idx += 1;
}
// source-region:
//
// **********
// | ~~~ |
// **********
// ^
// |-- closure.source() / first_src_addr
//
//
// ~~~ : live words
//
// destination-region:
//
// **********
// | |
// **********
// ^
// |-- region-start
if (bitmap->is_unmarked(closure.source())) {
// An object overflows the previous destination region, so this
// destination region should copy the remainder of the object or as much as
// will fit.
HeapWord* const old_src_addr = closure.source();
{
HeapWord* region_start = sd.region_align_down(closure.source());
HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
HeapWord* obj_end;
if (obj_start != closure.source()) {
assert(bitmap->is_marked(obj_start), "inv");
// Found the actual obj-start, try to find the obj-end using either
// size() if this obj is completely contained in the current region.
HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
HeapWord* partial_obj_start = (next_region_start >= src_space_top)
? nullptr
: sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
// This obj extends to next region iff partial_obj_addr of the *next*
// region is the same as obj-start.
if (partial_obj_start == obj_start) {
// This obj extends to next region.
obj_end = partial_obj_end(next_region_start);
} else {
// Completely contained in this region; safe to use size().
obj_end = obj_start + cast_to_oop(obj_start)->size();
}
} else {
// This obj extends to current region.
obj_end = partial_obj_end(region_start);
}
size_t partial_obj_size = pointer_delta(obj_end, closure.source());
closure.copy_partial_obj(partial_obj_size);
}
if (closure.is_full()) {
decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
closure.complete_region(dest_addr, region_ptr);
return;
}
// Finished copying without using up the current destination-region
HeapWord* const end_addr = sd.region_align_down(closure.source());
if (sd.region_align_down(old_src_addr) != end_addr) {
assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
// The partial object was copied from more than one source region.
decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
// Move to the next source region, possibly switching spaces as well. All
// args except end_addr may be modified.
src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
}
}
// Handle the rest obj-by-obj, where we know obj-start.
do {
HeapWord* cur_addr = closure.source();
HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
src_space_top);
// To handle the case where the final obj in source region extends to next region.
HeapWord* final_obj_start = (end_addr == src_space_top)
? nullptr
: sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
// Apply closure on objs inside [cur_addr, end_addr)
do {
cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
if (cur_addr == end_addr) {
break;
}
size_t obj_size;
if (final_obj_start == cur_addr) {
obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
} else {
// This obj doesn't extend into next region; size() is safe to use.
obj_size = cast_to_oop(cur_addr)->size();
}
closure.do_addr(cur_addr, obj_size);
cur_addr += obj_size;
} while (cur_addr < end_addr && !closure.is_full());
if (closure.is_full()) {
decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
closure.complete_region(dest_addr, region_ptr);
return;
}
decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
// Move to the next source region, possibly switching spaces as well. All
// args except end_addr may be modified.
src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
} while (true);
}
void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
{
MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
fill_region(cm, cl, region_idx);
}
void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
{
// Get a shadow region first
ParallelCompactData& sd = summary_data();
RegionData* const region_ptr = sd.region(region_idx);
size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
// The InvalidShadow return value indicates the corresponding heap region is available,
// so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
// MoveAndUpdateShadowClosure to fill the acquired shadow region.
if (shadow_region == ParCompactionManager::InvalidShadow) {
MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
region_ptr->shadow_to_normal();
return fill_region(cm, cl, region_idx);
} else {
MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
return fill_region(cm, cl, region_idx);
}
}
void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
{
Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
}
bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t &region_idx)
{
size_t next = cm->next_shadow_region();
ParallelCompactData& sd = summary_data();
size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
while (next < old_new_top) {
if (sd.region(next)->mark_shadow()) {
region_idx = next;
return true;
}
next = cm->move_next_shadow_region_by(active_gc_threads);
}
return false;
}
// The shadow region is an optimization to address region dependencies in full GC. The basic
// idea is making more regions available by temporally storing their live objects in empty
// shadow regions to resolve dependencies between them and the destination regions. Therefore,
// GC threads need not wait destination regions to be available before processing sources.
//
// A typical workflow would be:
// After draining its own stack and failing to steal from others, a GC worker would pick an
// unavailable region (destination count > 0) and get a shadow region. Then the worker fills
// the shadow region by copying live objects from source regions of the unavailable one. Once
// the unavailable region becomes available, the data in the shadow region will be copied back.
// Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
{
const ParallelCompactData& sd = PSParallelCompact::summary_data();
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
SpaceInfo* const space_info = _space_info + id;
MutableSpace* const space = space_info->space();
const size_t beg_region =
sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
const size_t end_region =
sd.addr_to_region_idx(sd.region_align_down(space->end()));
for (size_t cur = beg_region; cur < end_region; ++cur) {
ParCompactionManager::push_shadow_region(cur);
}
}
size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
for (uint i = 0; i < parallel_gc_threads; i++) {
ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
cm->set_next_shadow_region(beg_region + i);
}
}
void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
{
size_t words = MIN2(partial_obj_size, words_remaining());
// This test is necessary; if omitted, the pointer updates to a partial object
// that crosses the dense prefix boundary could be overwritten.
if (source() != copy_destination()) {
DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
Copy::aligned_conjoint_words(source(), copy_destination(), words);
}
update_state(words);
}
void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
region_ptr->set_completed();
}
void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
assert(destination() != nullptr, "sanity");
_source = addr;
// The start_array must be updated even if the object is not moving.
if (_start_array != nullptr) {
_start_array->update_for_block(destination(), destination() + words);
}
// Avoid overflow
words = MIN2(words, words_remaining());
assert(words > 0, "inv");
if (copy_destination() != source()) {
DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
assert(source() != destination(), "inv");
assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
Copy::aligned_conjoint_words(source(), copy_destination(), words);
cast_to_oop(copy_destination())->init_mark();
}
update_state(words);
}
void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
// Record the shadow region index
region_ptr->set_shadow_region(_shadow);
// Mark the shadow region as filled to indicate the data is ready to be
// copied back
region_ptr->mark_filled();
// Try to copy the content of the shadow region back to its corresponding
// heap region if available; the GC thread that decreases the destination
// count to zero will do the copying otherwise (see
// PSParallelCompact::decrement_destination_counts).
if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
region_ptr->set_completed();
PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
ParCompactionManager::push_shadow_region_mt_safe(_shadow);
}
}