src/hotspot/share/gc/parallel/psOldGen.cpp - toolchain/jdk/jdk21 - Git at Google

 /*
  * 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
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #include "precompiled.hpp"
 #include "gc/parallel/objectStartArray.inline.hpp"
 #include "gc/parallel/parallelArguments.hpp"
 #include "gc/parallel/parallelScavengeHeap.hpp"
 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
 #include "gc/parallel/psCardTable.hpp"
 #include "gc/parallel/psOldGen.hpp"
 #include "gc/shared/cardTableBarrierSet.hpp"
 #include "gc/shared/gcLocker.hpp"
 #include "gc/shared/spaceDecorator.inline.hpp"
 #include "logging/log.hpp"
 #include "oops/oop.inline.hpp"
 #include "runtime/java.hpp"
 #include "utilities/align.hpp"

 PSOldGen::PSOldGen(ReservedSpace rs, size_t initial_size, size_t min_size,
                    size_t max_size, const char* perf_data_name, int level):
   _min_gen_size(min_size),
   _max_gen_size(max_size)
 {
   initialize(rs, initial_size, GenAlignment, perf_data_name, level);
 }

 void PSOldGen::initialize(ReservedSpace rs, size_t initial_size, size_t alignment,
                           const char* perf_data_name, int level) {
   initialize_virtual_space(rs, initial_size, alignment);
   initialize_work(perf_data_name, level);

   initialize_performance_counters(perf_data_name, level);
 }

 void PSOldGen::initialize_virtual_space(ReservedSpace rs,
                                         size_t initial_size,
                                         size_t alignment) {

   _virtual_space = new PSVirtualSpace(rs, alignment);
   if (!_virtual_space->expand_by(initial_size)) {
     vm_exit_during_initialization("Could not reserve enough space for "
                                   "object heap");
   }
 }

 void PSOldGen::initialize_work(const char* perf_data_name, int level) {
   MemRegion const reserved_mr = reserved();
   assert(reserved_mr.byte_size() == max_gen_size(), "invariant");

   // Object start stuff: for all reserved memory
   start_array()->initialize(reserved_mr);

   // Card table stuff: for all committed memory
   MemRegion committed_mr((HeapWord*)virtual_space()->low(),
                          (HeapWord*)virtual_space()->high());

   if (ZapUnusedHeapArea) {
     // Mangle newly committed space immediately rather than
     // waiting for the initialization of the space even though
     // mangling is related to spaces.  Doing it here eliminates
     // the need to carry along information that a complete mangling
     // (bottom to end) needs to be done.
     SpaceMangler::mangle_region(committed_mr);
   }

   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
   PSCardTable* ct = heap->card_table();
   ct->resize_covered_region(committed_mr);

   // Verify that the start and end of this generation is the start of a card.
   // If this wasn't true, a single card could span more than one generation,
   // which would cause problems when we commit/uncommit memory, and when we
   // clear and dirty cards.
   guarantee(ct->is_card_aligned(reserved_mr.start()), "generation must be card aligned");
   // Check the heap layout documented at `class ParallelScavengeHeap`.
   assert(reserved_mr.end() != heap->reserved_region().end(), "invariant");
   guarantee(ct->is_card_aligned(reserved_mr.end()), "generation must be card aligned");

   //
   // ObjectSpace stuff
   //

   _object_space = new MutableSpace(virtual_space()->alignment());
   object_space()->initialize(committed_mr,
                              SpaceDecorator::Clear,
                              SpaceDecorator::Mangle,
                              MutableSpace::SetupPages,
                              &ParallelScavengeHeap::heap()->workers());

   // Update the start_array
   start_array()->set_covered_region(committed_mr);
 }

 void PSOldGen::initialize_performance_counters(const char* perf_data_name, int level) {
   // Generation Counters, generation 'level', 1 subspace
   _gen_counters = new PSGenerationCounters(perf_data_name, level, 1, min_gen_size(),
                                            max_gen_size(), virtual_space());
   _space_counters = new SpaceCounters(perf_data_name, 0,
                                       virtual_space()->reserved_size(),
                                       _object_space, _gen_counters);
 }

 // Assume that the generation has been allocated if its
 // reserved size is not 0.
 bool  PSOldGen::is_allocated() {
   return virtual_space()->reserved_size() != 0;
 }

 size_t PSOldGen::num_iterable_blocks() const {
   return (object_space()->used_in_bytes() + IterateBlockSize - 1) / IterateBlockSize;
 }

 void PSOldGen::object_iterate_block(ObjectClosure* cl, size_t block_index) {
   size_t block_word_size = IterateBlockSize / HeapWordSize;
   assert((block_word_size % (ObjectStartArray::card_size())) == 0,
          "Block size not a multiple of start_array block");

   MutableSpace *space = object_space();

   HeapWord* begin = space->bottom() + block_index * block_word_size;
   HeapWord* end = MIN2(space->top(), begin + block_word_size);

   if (!start_array()->object_starts_in_range(begin, end)) {
     return;
   }

   // Get object starting at or reaching into this block.
   HeapWord* start = start_array()->object_start(begin);
   if (start < begin) {
     start += cast_to_oop(start)->size();
   }
   assert(start >= begin,
          "Object address" PTR_FORMAT " must be larger or equal to block address at " PTR_FORMAT,
          p2i(start), p2i(begin));
   // Iterate all objects until the end.
   for (HeapWord* p = start; p < end; p += cast_to_oop(p)->size()) {
     cl->do_object(cast_to_oop(p));
   }
 }

 bool PSOldGen::expand_for_allocate(size_t word_size) {
   assert(word_size > 0, "allocating zero words?");
   bool result = true;
   {
     MutexLocker x(PSOldGenExpand_lock);
     // Avoid "expand storms" by rechecking available space after obtaining
     // the lock, because another thread may have already made sufficient
     // space available.  If insufficient space available, that will remain
     // true until we expand, since we have the lock.  Other threads may take
     // the space we need before we can allocate it, regardless of whether we
     // expand.  That's okay, we'll just try expanding again.
     if (object_space()->needs_expand(word_size)) {
       result = expand(word_size*HeapWordSize);
     }
   }
   if (GCExpandToAllocateDelayMillis > 0) {
     os::naked_sleep(GCExpandToAllocateDelayMillis);
   }
   return result;
 }

 bool PSOldGen::expand(size_t bytes) {
   assert_lock_strong(PSOldGenExpand_lock);
   assert_locked_or_safepoint(Heap_lock);
   assert(bytes > 0, "precondition");
   const size_t alignment = virtual_space()->alignment();
   size_t aligned_bytes  = align_up(bytes, alignment);
   size_t aligned_expand_bytes = align_up(MinHeapDeltaBytes, alignment);

   if (UseNUMA) {
     // With NUMA we use round-robin page allocation for the old gen. Expand by at least
     // providing a page per lgroup. Alignment is larger or equal to the page size.
     aligned_expand_bytes = MAX2(aligned_expand_bytes, alignment * os::numa_get_groups_num());
   }
   if (aligned_bytes == 0) {
     // The alignment caused the number of bytes to wrap.  A call to expand
     // implies a best effort to expand by "bytes" but not a guarantee.  Align
     // down to give a best effort.  This is likely the most that the generation
     // can expand since it has some capacity to start with.
     aligned_bytes = align_down(bytes, alignment);
   }

   bool success = false;
   if (aligned_expand_bytes > aligned_bytes) {
     success = expand_by(aligned_expand_bytes);
   }
   if (!success) {
     success = expand_by(aligned_bytes);
   }
   if (!success) {
     success = expand_to_reserved();
   }

   if (success && GCLocker::is_active_and_needs_gc()) {
     log_debug(gc)("Garbage collection disabled, expanded heap instead");
   }
   return success;
 }

 bool PSOldGen::expand_by(size_t bytes) {
   assert_lock_strong(PSOldGenExpand_lock);
   assert_locked_or_safepoint(Heap_lock);
   assert(bytes > 0, "precondition");
   bool result = virtual_space()->expand_by(bytes);
   if (result) {
     if (ZapUnusedHeapArea) {
       // We need to mangle the newly expanded area. The memregion spans
       // end -> new_end, we assume that top -> end is already mangled.
       // Do the mangling before post_resize() is called because
       // the space is available for allocation after post_resize();
       HeapWord* const virtual_space_high = (HeapWord*) virtual_space()->high();
       assert(object_space()->end() < virtual_space_high,
         "Should be true before post_resize()");
       MemRegion mangle_region(object_space()->end(), virtual_space_high);
       // Note that the object space has not yet been updated to
       // coincide with the new underlying virtual space.
       SpaceMangler::mangle_region(mangle_region);
     }
     post_resize();
     if (UsePerfData) {
       _space_counters->update_capacity();
       _gen_counters->update_all();
     }
   }

   if (result) {
     size_t new_mem_size = virtual_space()->committed_size();
     size_t old_mem_size = new_mem_size - bytes;
     log_debug(gc)("Expanding %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K",
                   name(), old_mem_size/K, bytes/K, new_mem_size/K);
   }

   return result;
 }

 bool PSOldGen::expand_to_reserved() {
   assert_lock_strong(PSOldGenExpand_lock);
   assert_locked_or_safepoint(Heap_lock);

   bool result = false;
   const size_t remaining_bytes = virtual_space()->uncommitted_size();
   if (remaining_bytes > 0) {
     result = expand_by(remaining_bytes);
     DEBUG_ONLY(if (!result) log_warning(gc)("grow to reserve failed"));
   }
   return result;
 }

 void PSOldGen::shrink(size_t bytes) {
   assert_lock_strong(PSOldGenExpand_lock);
   assert_locked_or_safepoint(Heap_lock);

   size_t size = align_down(bytes, virtual_space()->alignment());
   if (size > 0) {
     virtual_space()->shrink_by(bytes);
     post_resize();

     size_t new_mem_size = virtual_space()->committed_size();
     size_t old_mem_size = new_mem_size + bytes;
     log_debug(gc)("Shrinking %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K",
                   name(), old_mem_size/K, bytes/K, new_mem_size/K);
   }
 }

 void PSOldGen::complete_loaded_archive_space(MemRegion archive_space) {
   HeapWord* cur = archive_space.start();
   while (cur < archive_space.end()) {
     _start_array.allocate_block(cur);
     size_t word_size = cast_to_oop(cur)->size();
     cur += word_size;
   }
 }

 void PSOldGen::resize(size_t desired_free_space) {
   const size_t alignment = virtual_space()->alignment();
   const size_t size_before = virtual_space()->committed_size();
   size_t new_size = used_in_bytes() + desired_free_space;
   if (new_size < used_in_bytes()) {
     // Overflowed the addition.
     new_size = max_gen_size();
   }
   // Adjust according to our min and max
   new_size = clamp(new_size, min_gen_size(), max_gen_size());

   new_size = align_up(new_size, alignment);

   const size_t current_size = capacity_in_bytes();

   log_trace(gc, ergo)("AdaptiveSizePolicy::old generation size: "
     "desired free: " SIZE_FORMAT " used: " SIZE_FORMAT
     " new size: " SIZE_FORMAT " current size " SIZE_FORMAT
     " gen limits: " SIZE_FORMAT " / " SIZE_FORMAT,
     desired_free_space, used_in_bytes(), new_size, current_size,
     max_gen_size(), min_gen_size());

   if (new_size == current_size) {
     // No change requested
     return;
   }
   if (new_size > current_size) {
     size_t change_bytes = new_size - current_size;
     MutexLocker x(PSOldGenExpand_lock);
     expand(change_bytes);
   } else {
     size_t change_bytes = current_size - new_size;
     MutexLocker x(PSOldGenExpand_lock);
     shrink(change_bytes);
   }

   log_trace(gc, ergo)("AdaptiveSizePolicy::old generation size: collection: %d (" SIZE_FORMAT ") -> (" SIZE_FORMAT ") ",
                       ParallelScavengeHeap::heap()->total_collections(),
                       size_before,
                       virtual_space()->committed_size());
 }

 // NOTE! We need to be careful about resizing. During a GC, multiple
 // allocators may be active during heap expansion. If we allow the
 // heap resizing to become visible before we have correctly resized
 // all heap related data structures, we may cause program failures.
 void PSOldGen::post_resize() {
   // First construct a memregion representing the new size
   MemRegion new_memregion((HeapWord*)virtual_space()->low(),
     (HeapWord*)virtual_space()->high());
   size_t new_word_size = new_memregion.word_size();

   start_array()->set_covered_region(new_memregion);
   ParallelScavengeHeap::heap()->card_table()->resize_covered_region(new_memregion);

   WorkerThreads* workers = Thread::current()->is_VM_thread() ?
                       &ParallelScavengeHeap::heap()->workers() : nullptr;

   // The update of the space's end is done by this call.  As that
   // makes the new space available for concurrent allocation, this
   // must be the last step when expanding.
   object_space()->initialize(new_memregion,
                              SpaceDecorator::DontClear,
                              SpaceDecorator::DontMangle,
                              MutableSpace::SetupPages,
                              workers);

   assert(new_word_size == heap_word_size(object_space()->capacity_in_bytes()),
     "Sanity");
 }

 void PSOldGen::print() const { print_on(tty);}
 void PSOldGen::print_on(outputStream* st) const {
   st->print(" %-15s", name());
   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
               capacity_in_bytes()/K, used_in_bytes()/K);
   st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
                 p2i(virtual_space()->low_boundary()),
                 p2i(virtual_space()->high()),
                 p2i(virtual_space()->high_boundary()));

   st->print("  object"); object_space()->print_on(st);
 }

 void PSOldGen::update_counters() {
   if (UsePerfData) {
     _space_counters->update_all();
     _gen_counters->update_all();
   }
 }

 void PSOldGen::verify() {
   object_space()->verify();
 }

 class VerifyObjectStartArrayClosure : public ObjectClosure {
   ObjectStartArray* _start_array;

  public:
   VerifyObjectStartArrayClosure(ObjectStartArray* start_array) :
     _start_array(start_array) { }

   virtual void do_object(oop obj) {
     HeapWord* test_addr = cast_from_oop<HeapWord*>(obj) + 1;
     guarantee(_start_array->object_start(test_addr) == cast_from_oop<HeapWord*>(obj), "ObjectStartArray cannot find start of object");
     guarantee(_start_array->is_block_allocated(cast_from_oop<HeapWord*>(obj)), "ObjectStartArray missing block allocation");
   }
 };

 void PSOldGen::verify_object_start_array() {
   VerifyObjectStartArrayClosure check(&_start_array);
   object_iterate(&check);
 }

 #ifndef PRODUCT
 void PSOldGen::record_spaces_top() {
   assert(ZapUnusedHeapArea, "Not mangling unused space");
   object_space()->set_top_for_allocations();
 }
 #endif
	/*
	* 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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#include "precompiled.hpp"
	#include "gc/parallel/objectStartArray.inline.hpp"
	#include "gc/parallel/parallelArguments.hpp"
	#include "gc/parallel/parallelScavengeHeap.hpp"
	#include "gc/parallel/psAdaptiveSizePolicy.hpp"
	#include "gc/parallel/psCardTable.hpp"
	#include "gc/parallel/psOldGen.hpp"
	#include "gc/shared/cardTableBarrierSet.hpp"
	#include "gc/shared/gcLocker.hpp"
	#include "gc/shared/spaceDecorator.inline.hpp"
	#include "logging/log.hpp"
	#include "oops/oop.inline.hpp"
	#include "runtime/java.hpp"
	#include "utilities/align.hpp"

	PSOldGen::PSOldGen(ReservedSpace rs, size_t initial_size, size_t min_size,
	size_t max_size, const char* perf_data_name, int level):
	_min_gen_size(min_size),
	_max_gen_size(max_size)
	{
	initialize(rs, initial_size, GenAlignment, perf_data_name, level);
	}

	void PSOldGen::initialize(ReservedSpace rs, size_t initial_size, size_t alignment,
	const char* perf_data_name, int level) {
	initialize_virtual_space(rs, initial_size, alignment);
	initialize_work(perf_data_name, level);

	initialize_performance_counters(perf_data_name, level);
	}

	void PSOldGen::initialize_virtual_space(ReservedSpace rs,
	size_t initial_size,
	size_t alignment) {

	_virtual_space = new PSVirtualSpace(rs, alignment);
	if (!_virtual_space->expand_by(initial_size)) {
	vm_exit_during_initialization("Could not reserve enough space for "
	"object heap");
	}
	}

	void PSOldGen::initialize_work(const char* perf_data_name, int level) {
	MemRegion const reserved_mr = reserved();
	assert(reserved_mr.byte_size() == max_gen_size(), "invariant");

	// Object start stuff: for all reserved memory
	start_array()->initialize(reserved_mr);

	// Card table stuff: for all committed memory
	MemRegion committed_mr((HeapWord*)virtual_space()->low(),
	(HeapWord*)virtual_space()->high());

	if (ZapUnusedHeapArea) {
	// Mangle newly committed space immediately rather than
	// waiting for the initialization of the space even though
	// mangling is related to spaces. Doing it here eliminates
	// the need to carry along information that a complete mangling
	// (bottom to end) needs to be done.
	SpaceMangler::mangle_region(committed_mr);
	}

	ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
	PSCardTable* ct = heap->card_table();
	ct->resize_covered_region(committed_mr);

	// Verify that the start and end of this generation is the start of a card.
	// If this wasn't true, a single card could span more than one generation,
	// which would cause problems when we commit/uncommit memory, and when we
	// clear and dirty cards.
	guarantee(ct->is_card_aligned(reserved_mr.start()), "generation must be card aligned");
	// Check the heap layout documented at `class ParallelScavengeHeap`.
	assert(reserved_mr.end() != heap->reserved_region().end(), "invariant");
	guarantee(ct->is_card_aligned(reserved_mr.end()), "generation must be card aligned");

	//
	// ObjectSpace stuff
	//

	_object_space = new MutableSpace(virtual_space()->alignment());
	object_space()->initialize(committed_mr,
	SpaceDecorator::Clear,
	SpaceDecorator::Mangle,
	MutableSpace::SetupPages,
	&ParallelScavengeHeap::heap()->workers());

	// Update the start_array
	start_array()->set_covered_region(committed_mr);
	}

	void PSOldGen::initialize_performance_counters(const char* perf_data_name, int level) {
	// Generation Counters, generation 'level', 1 subspace
	_gen_counters = new PSGenerationCounters(perf_data_name, level, 1, min_gen_size(),
	max_gen_size(), virtual_space());
	_space_counters = new SpaceCounters(perf_data_name, 0,
	virtual_space()->reserved_size(),
	_object_space, _gen_counters);
	}

	// Assume that the generation has been allocated if its
	// reserved size is not 0.
	bool PSOldGen::is_allocated() {
	return virtual_space()->reserved_size() != 0;
	}

	size_t PSOldGen::num_iterable_blocks() const {
	return (object_space()->used_in_bytes() + IterateBlockSize - 1) / IterateBlockSize;
	}

	void PSOldGen::object_iterate_block(ObjectClosure* cl, size_t block_index) {
	size_t block_word_size = IterateBlockSize / HeapWordSize;
	assert((block_word_size % (ObjectStartArray::card_size())) == 0,
	"Block size not a multiple of start_array block");

	MutableSpace *space = object_space();

	HeapWord* begin = space->bottom() + block_index * block_word_size;
	HeapWord* end = MIN2(space->top(), begin + block_word_size);

	if (!start_array()->object_starts_in_range(begin, end)) {
	return;
	}

	// Get object starting at or reaching into this block.
	HeapWord* start = start_array()->object_start(begin);
	if (start < begin) {
	start += cast_to_oop(start)->size();
	}
	assert(start >= begin,
	"Object address" PTR_FORMAT " must be larger or equal to block address at " PTR_FORMAT,
	p2i(start), p2i(begin));
	// Iterate all objects until the end.
	for (HeapWord* p = start; p < end; p += cast_to_oop(p)->size()) {
	cl->do_object(cast_to_oop(p));
	}
	}

	bool PSOldGen::expand_for_allocate(size_t word_size) {
	assert(word_size > 0, "allocating zero words?");
	bool result = true;
	{
	MutexLocker x(PSOldGenExpand_lock);
	// Avoid "expand storms" by rechecking available space after obtaining
	// the lock, because another thread may have already made sufficient
	// space available. If insufficient space available, that will remain
	// true until we expand, since we have the lock. Other threads may take
	// the space we need before we can allocate it, regardless of whether we
	// expand. That's okay, we'll just try expanding again.
	if (object_space()->needs_expand(word_size)) {
	result = expand(word_size*HeapWordSize);
	}
	}
	if (GCExpandToAllocateDelayMillis > 0) {
	os::naked_sleep(GCExpandToAllocateDelayMillis);
	}
	return result;
	}

	bool PSOldGen::expand(size_t bytes) {
	assert_lock_strong(PSOldGenExpand_lock);
	assert_locked_or_safepoint(Heap_lock);
	assert(bytes > 0, "precondition");
	const size_t alignment = virtual_space()->alignment();
	size_t aligned_bytes = align_up(bytes, alignment);
	size_t aligned_expand_bytes = align_up(MinHeapDeltaBytes, alignment);

	if (UseNUMA) {
	// With NUMA we use round-robin page allocation for the old gen. Expand by at least
	// providing a page per lgroup. Alignment is larger or equal to the page size.
	aligned_expand_bytes = MAX2(aligned_expand_bytes, alignment * os::numa_get_groups_num());
	}
	if (aligned_bytes == 0) {
	// The alignment caused the number of bytes to wrap. A call to expand
	// implies a best effort to expand by "bytes" but not a guarantee. Align
	// down to give a best effort. This is likely the most that the generation
	// can expand since it has some capacity to start with.
	aligned_bytes = align_down(bytes, alignment);
	}

	bool success = false;
	if (aligned_expand_bytes > aligned_bytes) {
	success = expand_by(aligned_expand_bytes);
	}
	if (!success) {
	success = expand_by(aligned_bytes);
	}
	if (!success) {
	success = expand_to_reserved();
	}

	if (success && GCLocker::is_active_and_needs_gc()) {
	log_debug(gc)("Garbage collection disabled, expanded heap instead");
	}
	return success;
	}

	bool PSOldGen::expand_by(size_t bytes) {
	assert_lock_strong(PSOldGenExpand_lock);
	assert_locked_or_safepoint(Heap_lock);
	assert(bytes > 0, "precondition");
	bool result = virtual_space()->expand_by(bytes);
	if (result) {
	if (ZapUnusedHeapArea) {
	// We need to mangle the newly expanded area. The memregion spans
	// end -> new_end, we assume that top -> end is already mangled.
	// Do the mangling before post_resize() is called because
	// the space is available for allocation after post_resize();
	HeapWord* const virtual_space_high = (HeapWord*) virtual_space()->high();
	assert(object_space()->end() < virtual_space_high,
	"Should be true before post_resize()");
	MemRegion mangle_region(object_space()->end(), virtual_space_high);
	// Note that the object space has not yet been updated to
	// coincide with the new underlying virtual space.
	SpaceMangler::mangle_region(mangle_region);
	}
	post_resize();
	if (UsePerfData) {
	_space_counters->update_capacity();
	_gen_counters->update_all();
	}
	}

	if (result) {
	size_t new_mem_size = virtual_space()->committed_size();
	size_t old_mem_size = new_mem_size - bytes;
	log_debug(gc)("Expanding %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K",
	name(), old_mem_size/K, bytes/K, new_mem_size/K);
	}

	return result;
	}

	bool PSOldGen::expand_to_reserved() {
	assert_lock_strong(PSOldGenExpand_lock);
	assert_locked_or_safepoint(Heap_lock);

	bool result = false;
	const size_t remaining_bytes = virtual_space()->uncommitted_size();
	if (remaining_bytes > 0) {
	result = expand_by(remaining_bytes);
	DEBUG_ONLY(if (!result) log_warning(gc)("grow to reserve failed"));
	}
	return result;
	}

	void PSOldGen::shrink(size_t bytes) {
	assert_lock_strong(PSOldGenExpand_lock);
	assert_locked_or_safepoint(Heap_lock);

	size_t size = align_down(bytes, virtual_space()->alignment());
	if (size > 0) {
	virtual_space()->shrink_by(bytes);
	post_resize();

	size_t new_mem_size = virtual_space()->committed_size();
	size_t old_mem_size = new_mem_size + bytes;
	log_debug(gc)("Shrinking %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K",
	name(), old_mem_size/K, bytes/K, new_mem_size/K);
	}
	}

	void PSOldGen::complete_loaded_archive_space(MemRegion archive_space) {
	HeapWord* cur = archive_space.start();
	while (cur < archive_space.end()) {
	_start_array.allocate_block(cur);
	size_t word_size = cast_to_oop(cur)->size();
	cur += word_size;
	}
	}

	void PSOldGen::resize(size_t desired_free_space) {
	const size_t alignment = virtual_space()->alignment();
	const size_t size_before = virtual_space()->committed_size();
	size_t new_size = used_in_bytes() + desired_free_space;
	if (new_size < used_in_bytes()) {
	// Overflowed the addition.
	new_size = max_gen_size();
	}
	// Adjust according to our min and max
	new_size = clamp(new_size, min_gen_size(), max_gen_size());

	new_size = align_up(new_size, alignment);

	const size_t current_size = capacity_in_bytes();

	log_trace(gc, ergo)("AdaptiveSizePolicy::old generation size: "
	"desired free: " SIZE_FORMAT " used: " SIZE_FORMAT
	" new size: " SIZE_FORMAT " current size " SIZE_FORMAT
	" gen limits: " SIZE_FORMAT " / " SIZE_FORMAT,
	desired_free_space, used_in_bytes(), new_size, current_size,
	max_gen_size(), min_gen_size());

	if (new_size == current_size) {
	// No change requested
	return;
	}
	if (new_size > current_size) {
	size_t change_bytes = new_size - current_size;
	MutexLocker x(PSOldGenExpand_lock);
	expand(change_bytes);
	} else {
	size_t change_bytes = current_size - new_size;
	MutexLocker x(PSOldGenExpand_lock);
	shrink(change_bytes);
	}

	log_trace(gc, ergo)("AdaptiveSizePolicy::old generation size: collection: %d (" SIZE_FORMAT ") -> (" SIZE_FORMAT ") ",
	ParallelScavengeHeap::heap()->total_collections(),
	size_before,
	virtual_space()->committed_size());
	}

	// NOTE! We need to be careful about resizing. During a GC, multiple
	// allocators may be active during heap expansion. If we allow the
	// heap resizing to become visible before we have correctly resized
	// all heap related data structures, we may cause program failures.
	void PSOldGen::post_resize() {
	// First construct a memregion representing the new size
	MemRegion new_memregion((HeapWord*)virtual_space()->low(),
	(HeapWord*)virtual_space()->high());
	size_t new_word_size = new_memregion.word_size();

	start_array()->set_covered_region(new_memregion);
	ParallelScavengeHeap::heap()->card_table()->resize_covered_region(new_memregion);

	WorkerThreads* workers = Thread::current()->is_VM_thread() ?
	&ParallelScavengeHeap::heap()->workers() : nullptr;

	// The update of the space's end is done by this call. As that
	// makes the new space available for concurrent allocation, this
	// must be the last step when expanding.
	object_space()->initialize(new_memregion,
	SpaceDecorator::DontClear,
	SpaceDecorator::DontMangle,
	MutableSpace::SetupPages,
	workers);

	assert(new_word_size == heap_word_size(object_space()->capacity_in_bytes()),
	"Sanity");
	}

	void PSOldGen::print() const { print_on(tty);}
	void PSOldGen::print_on(outputStream* st) const {
	st->print(" %-15s", name());
	st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
	capacity_in_bytes()/K, used_in_bytes()/K);
	st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
	p2i(virtual_space()->low_boundary()),
	p2i(virtual_space()->high()),
	p2i(virtual_space()->high_boundary()));

	st->print(" object"); object_space()->print_on(st);
	}

	void PSOldGen::update_counters() {
	if (UsePerfData) {
	_space_counters->update_all();
	_gen_counters->update_all();
	}
	}

	void PSOldGen::verify() {
	object_space()->verify();
	}

	class VerifyObjectStartArrayClosure : public ObjectClosure {
	ObjectStartArray* _start_array;

	public:
	VerifyObjectStartArrayClosure(ObjectStartArray* start_array) :
	_start_array(start_array) { }

	virtual void do_object(oop obj) {
	HeapWord* test_addr = cast_from_oop<HeapWord*>(obj) + 1;
	guarantee(_start_array->object_start(test_addr) == cast_from_oop<HeapWord*>(obj), "ObjectStartArray cannot find start of object");
	guarantee(_start_array->is_block_allocated(cast_from_oop<HeapWord*>(obj)), "ObjectStartArray missing block allocation");
	}
	};

	void PSOldGen::verify_object_start_array() {
	VerifyObjectStartArrayClosure check(&_start_array);
	object_iterate(&check);
	}

	#ifndef PRODUCT
	void PSOldGen::record_spaces_top() {
	assert(ZapUnusedHeapArea, "Not mangling unused space");
	object_space()->set_top_for_allocations();
	}
	#endif