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sdk/runtime/vm/heap/pages.cc
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Ryan Macnak 0080a1a43b [vm, gc] Don't hold PageSpace::tasks_lock_ while visiting remembered cards. 
The scavenger may abort while visiting the remembered cards if we run out of memory. The longjmp implementing this abort would skip ~MonitorLocker, leaving the monitor locked and (in debug mode) Thread::no_safepoint_scope_ unbalanced.

TEST=fragmentation_test
Bug: https://github.com/dart-lang/sdk/issues/45059
Change-Id: I63d77709c8d8948b5827f7ecde5b0ecb3af9a245
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/186640
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Liam Appelbe <liama@google.com>
2021-02-23 22:28:01 +00:00

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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/heap/pages.h"
#include "platform/assert.h"
#include "platform/leak_sanitizer.h"
#include "vm/dart.h"
#include "vm/heap/become.h"
#include "vm/heap/compactor.h"
#include "vm/heap/marker.h"
#include "vm/heap/safepoint.h"
#include "vm/heap/sweeper.h"
#include "vm/lockers.h"
#include "vm/log.h"
#include "vm/object.h"
#include "vm/object_set.h"
#include "vm/os_thread.h"
#include "vm/virtual_memory.h"
namespace dart {
DEFINE_FLAG(int,
old_gen_growth_space_ratio,
20,
"The desired maximum percentage of free space after old gen GC");
DEFINE_FLAG(int,
old_gen_growth_time_ratio,
3,
"The desired maximum percentage of time spent in old gen GC");
DEFINE_FLAG(int,
old_gen_growth_rate,
280,
"The max number of pages the old generation can grow at a time");
DEFINE_FLAG(bool,
print_free_list_before_gc,
false,
"Print free list statistics before a GC");
DEFINE_FLAG(bool,
print_free_list_after_gc,
false,
"Print free list statistics after a GC");
DEFINE_FLAG(bool, log_growth, false, "Log PageSpace growth policy decisions.");
OldPage* OldPage::Allocate(intptr_t size_in_words,
PageType type,
const char* name) {
const bool executable = type == kExecutable;
VirtualMemory* memory = VirtualMemory::AllocateAligned(
size_in_words << kWordSizeLog2, kOldPageSize, executable, name);
if (memory == NULL) {
return NULL;
}
OldPage* result = reinterpret_cast<OldPage*>(memory->address());
ASSERT(result != NULL);
result->memory_ = memory;
result->next_ = NULL;
result->used_in_bytes_ = 0;
result->forwarding_page_ = NULL;
result->card_table_ = NULL;
result->type_ = type;
LSAN_REGISTER_ROOT_REGION(result, sizeof(*result));
return result;
}
void OldPage::Deallocate() {
if (card_table_ != NULL) {
free(card_table_);
card_table_ = NULL;
}
bool image_page = is_image_page();
if (!image_page) {
LSAN_UNREGISTER_ROOT_REGION(this, sizeof(*this));
}
// For a regular heap pages, the memory for this object will become
// unavailable after the delete below.
delete memory_;
// For a heap page from a snapshot, the OldPage object lives in the malloc
// heap rather than the page itself.
if (image_page) {
free(this);
}
}
void OldPage::VisitObjects(ObjectVisitor* visitor) const {
ASSERT(Thread::Current()->IsAtSafepoint());
NoSafepointScope no_safepoint;
uword obj_addr = object_start();
uword end_addr = object_end();
while (obj_addr < end_addr) {
ObjectPtr raw_obj = UntaggedObject::FromAddr(obj_addr);
visitor->VisitObject(raw_obj);
obj_addr += raw_obj->untag()->HeapSize();
}
ASSERT(obj_addr == end_addr);
}
void OldPage::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
ASSERT(Thread::Current()->IsAtSafepoint() ||
(Thread::Current()->task_kind() == Thread::kCompactorTask));
NoSafepointScope no_safepoint;
uword obj_addr = object_start();
uword end_addr = object_end();
while (obj_addr < end_addr) {
ObjectPtr raw_obj = UntaggedObject::FromAddr(obj_addr);
obj_addr += raw_obj->untag()->VisitPointers(visitor);
}
ASSERT(obj_addr == end_addr);
}
void OldPage::VisitRememberedCards(ObjectPointerVisitor* visitor) {
ASSERT(Thread::Current()->IsAtSafepoint() ||
(Thread::Current()->task_kind() == Thread::kScavengerTask));
NoSafepointScope no_safepoint;
if (card_table_ == NULL) {
return;
}
bool table_is_empty = false;
ArrayPtr obj =
static_cast<ArrayPtr>(UntaggedObject::FromAddr(object_start()));
ASSERT(obj->IsArray());
ASSERT(obj->untag()->IsCardRemembered());
ObjectPtr* obj_from = obj->untag()->from();
ObjectPtr* obj_to = obj->untag()->to(Smi::Value(obj->untag()->length_));
const intptr_t size = card_table_size();
for (intptr_t i = 0; i < size; i++) {
if (card_table_[i] != 0) {
ObjectPtr* card_from =
reinterpret_cast<ObjectPtr*>(this) + (i << kSlotsPerCardLog2);
ObjectPtr* card_to = reinterpret_cast<ObjectPtr*>(card_from) +
(1 << kSlotsPerCardLog2) - 1;
// Minus 1 because to is inclusive.
if (card_from < obj_from) {
// First card overlaps with header.
card_from = obj_from;
}
if (card_to > obj_to) {
// Last card(s) may extend past the object. Array truncation can make
// this happen for more than one card.
card_to = obj_to;
}
visitor->VisitPointers(card_from, card_to);
bool has_new_target = false;
for (ObjectPtr* slot = card_from; slot <= card_to; slot++) {
if ((*slot)->IsNewObjectMayBeSmi()) {
has_new_target = true;
break;
}
}
if (has_new_target) {
// Card remains remembered.
table_is_empty = false;
} else {
card_table_[i] = 0;
}
}
}
if (table_is_empty) {
free(card_table_);
card_table_ = NULL;
}
}
ObjectPtr OldPage::FindObject(FindObjectVisitor* visitor) const {
uword obj_addr = object_start();
uword end_addr = object_end();
if (visitor->VisitRange(obj_addr, end_addr)) {
while (obj_addr < end_addr) {
ObjectPtr raw_obj = UntaggedObject::FromAddr(obj_addr);
uword next_obj_addr = obj_addr + raw_obj->untag()->HeapSize();
if (visitor->VisitRange(obj_addr, next_obj_addr) &&
raw_obj->untag()->FindObject(visitor)) {
return raw_obj; // Found object, return it.
}
obj_addr = next_obj_addr;
}
ASSERT(obj_addr == end_addr);
}
return Object::null();
}
void OldPage::WriteProtect(bool read_only) {
ASSERT(!is_image_page());
VirtualMemory::Protection prot;
if (read_only) {
if ((type_ == kExecutable) && (memory_->AliasOffset() == 0)) {
prot = VirtualMemory::kReadExecute;
} else {
prot = VirtualMemory::kReadOnly;
}
} else {
prot = VirtualMemory::kReadWrite;
}
memory_->Protect(prot);
}
// The initial estimate of how many words we can mark per microsecond (usage
// before / mark-sweep time). This is a conservative value observed running
// Flutter on a Nexus 4. After the first mark-sweep, we instead use a value
// based on the device's actual speed.
static const intptr_t kConservativeInitialMarkSpeed = 20;
PageSpace::PageSpace(Heap* heap, intptr_t max_capacity_in_words)
: heap_(heap),
num_freelists_(Utils::Maximum(FLAG_scavenger_tasks, 1) + 1),
freelists_(new FreeList[num_freelists_]),
pages_lock_(),
max_capacity_in_words_(max_capacity_in_words),
usage_(),
allocated_black_in_words_(0),
tasks_lock_(),
tasks_(0),
concurrent_marker_tasks_(0),
phase_(kDone),
#if defined(DEBUG)
iterating_thread_(NULL),
#endif
page_space_controller_(heap,
FLAG_old_gen_growth_space_ratio,
FLAG_old_gen_growth_rate,
FLAG_old_gen_growth_time_ratio),
marker_(NULL),
gc_time_micros_(0),
collections_(0),
mark_words_per_micro_(kConservativeInitialMarkSpeed),
enable_concurrent_mark_(FLAG_concurrent_mark) {
// We aren't holding the lock but no one can reference us yet.
UpdateMaxCapacityLocked();
UpdateMaxUsed();
for (intptr_t i = 0; i < num_freelists_; i++) {
freelists_[i].Reset();
}
TryReserveForOOM();
}
PageSpace::~PageSpace() {
{
MonitorLocker ml(tasks_lock());
while (tasks() > 0) {
ml.Wait();
}
}
FreePages(pages_);
FreePages(exec_pages_);
FreePages(large_pages_);
FreePages(image_pages_);
ASSERT(marker_ == NULL);
delete[] freelists_;
}
intptr_t PageSpace::LargePageSizeInWordsFor(intptr_t size) {
intptr_t page_size = Utils::RoundUp(size + OldPage::ObjectStartOffset(),
VirtualMemory::PageSize());
return page_size >> kWordSizeLog2;
}
void PageSpace::AddPageLocked(OldPage* page) {
if (pages_ == nullptr) {
pages_ = page;
} else {
pages_tail_->set_next(page);
}
pages_tail_ = page;
}
void PageSpace::AddLargePageLocked(OldPage* page) {
if (large_pages_ == nullptr) {
large_pages_ = page;
} else {
large_pages_tail_->set_next(page);
}
large_pages_tail_ = page;
}
void PageSpace::AddExecPageLocked(OldPage* page) {
if (exec_pages_ == nullptr) {
exec_pages_ = page;
} else {
if (FLAG_write_protect_code) {
exec_pages_tail_->WriteProtect(false);
}
exec_pages_tail_->set_next(page);
if (FLAG_write_protect_code) {
exec_pages_tail_->WriteProtect(true);
}
}
exec_pages_tail_ = page;
}
void PageSpace::RemovePageLocked(OldPage* page, OldPage* previous_page) {
if (previous_page != NULL) {
previous_page->set_next(page->next());
} else {
pages_ = page->next();
}
if (page == pages_tail_) {
pages_tail_ = previous_page;
}
}
void PageSpace::RemoveLargePageLocked(OldPage* page, OldPage* previous_page) {
if (previous_page != NULL) {
previous_page->set_next(page->next());
} else {
large_pages_ = page->next();
}
if (page == large_pages_tail_) {
large_pages_tail_ = previous_page;
}
}
void PageSpace::RemoveExecPageLocked(OldPage* page, OldPage* previous_page) {
if (previous_page != NULL) {
previous_page->set_next(page->next());
} else {
exec_pages_ = page->next();
}
if (page == exec_pages_tail_) {
exec_pages_tail_ = previous_page;
}
}
OldPage* PageSpace::AllocatePage(OldPage::PageType type, bool link) {
{
MutexLocker ml(&pages_lock_);
if (!CanIncreaseCapacityInWordsLocked(kOldPageSizeInWords)) {
return nullptr;
}
IncreaseCapacityInWordsLocked(kOldPageSizeInWords);
}
const bool is_exec = (type == OldPage::kExecutable);
const char* name = Heap::RegionName(is_exec ? Heap::kCode : Heap::kOld);
OldPage* page = OldPage::Allocate(kOldPageSizeInWords, type, name);
if (page == nullptr) {
RELEASE_ASSERT(!FLAG_abort_on_oom);
IncreaseCapacityInWords(-kOldPageSizeInWords);
return nullptr;
}
MutexLocker ml(&pages_lock_);
if (link) {
if (is_exec) {
AddExecPageLocked(page);
} else {
AddPageLocked(page);
}
}
page->set_object_end(page->memory_->end());
if ((type != OldPage::kExecutable) && (heap_ != nullptr) &&
(!heap_->is_vm_isolate())) {
page->AllocateForwardingPage();
}
return page;
}
OldPage* PageSpace::AllocateLargePage(intptr_t size, OldPage::PageType type) {
const intptr_t page_size_in_words = LargePageSizeInWordsFor(size);
{
MutexLocker ml(&pages_lock_);
if (!CanIncreaseCapacityInWordsLocked(page_size_in_words)) {
return nullptr;
}
IncreaseCapacityInWordsLocked(page_size_in_words);
}
const bool is_exec = (type == OldPage::kExecutable);
const char* name = Heap::RegionName(is_exec ? Heap::kCode : Heap::kOld);
OldPage* page = OldPage::Allocate(page_size_in_words, type, name);
MutexLocker ml(&pages_lock_);
if (page == nullptr) {
IncreaseCapacityInWordsLocked(-page_size_in_words);
return nullptr;
} else {
intptr_t actual_size_in_words = page->memory_->size() >> kWordSizeLog2;
if (actual_size_in_words != page_size_in_words) {
IncreaseCapacityInWordsLocked(actual_size_in_words - page_size_in_words);
}
}
if (is_exec) {
AddExecPageLocked(page);
} else {
AddLargePageLocked(page);
}
// Only one object in this page (at least until Array::MakeFixedLength
// is called).
page->set_object_end(page->object_start() + size);
return page;
}
void PageSpace::TruncateLargePage(OldPage* page,
intptr_t new_object_size_in_bytes) {
const intptr_t old_object_size_in_bytes =
page->object_end() - page->object_start();
ASSERT(new_object_size_in_bytes <= old_object_size_in_bytes);
const intptr_t new_page_size_in_words =
LargePageSizeInWordsFor(new_object_size_in_bytes);
VirtualMemory* memory = page->memory_;
const intptr_t old_page_size_in_words = (memory->size() >> kWordSizeLog2);
if (new_page_size_in_words < old_page_size_in_words) {
memory->Truncate(new_page_size_in_words << kWordSizeLog2);
IncreaseCapacityInWords(new_page_size_in_words - old_page_size_in_words);
page->set_object_end(page->object_start() + new_object_size_in_bytes);
}
}
void PageSpace::FreePage(OldPage* page, OldPage* previous_page) {
bool is_exec = (page->type() == OldPage::kExecutable);
{
MutexLocker ml(&pages_lock_);
IncreaseCapacityInWordsLocked(-(page->memory_->size() >> kWordSizeLog2));
if (is_exec) {
RemoveExecPageLocked(page, previous_page);
} else {
RemovePageLocked(page, previous_page);
}
}
// TODO(iposva): Consider adding to a pool of empty pages.
page->Deallocate();
}
void PageSpace::FreeLargePage(OldPage* page, OldPage* previous_page) {
ASSERT(page->type() != OldPage::kExecutable);
MutexLocker ml(&pages_lock_);
IncreaseCapacityInWordsLocked(-(page->memory_->size() >> kWordSizeLog2));
RemoveLargePageLocked(page, previous_page);
page->Deallocate();
}
void PageSpace::FreePages(OldPage* pages) {
OldPage* page = pages;
while (page != NULL) {
OldPage* next = page->next();
page->Deallocate();
page = next;
}
}
void PageSpace::EvaluateConcurrentMarking(GrowthPolicy growth_policy) {
if (growth_policy != kForceGrowth) {
ASSERT(GrowthControlState());
if (heap_ != NULL) { // Some unit tests.
Thread* thread = Thread::Current();
if (thread->CanCollectGarbage()) {
heap_->CheckFinishConcurrentMarking(thread);
heap_->CheckStartConcurrentMarking(thread, Heap::kOldSpace);
}
}
}
}
uword PageSpace::TryAllocateInFreshPage(intptr_t size,
FreeList* freelist,
OldPage::PageType type,
GrowthPolicy growth_policy,
bool is_locked) {
ASSERT(Heap::IsAllocatableViaFreeLists(size));
EvaluateConcurrentMarking(growth_policy);
uword result = 0;
SpaceUsage after_allocation = GetCurrentUsage();
after_allocation.used_in_words += size >> kWordSizeLog2;
// Can we grow by one page?
after_allocation.capacity_in_words += kOldPageSizeInWords;
if (growth_policy == kForceGrowth ||
!page_space_controller_.ReachedHardThreshold(after_allocation)) {
OldPage* page = AllocatePage(type);
if (page == NULL) {
return 0;
}
// Start of the newly allocated page is the allocated object.
result = page->object_start();
// Note: usage_.capacity_in_words is increased by AllocatePage.
usage_.used_in_words += (size >> kWordSizeLog2);
// Enqueue the remainder in the free list.
uword free_start = result + size;
intptr_t free_size = page->object_end() - free_start;
if (free_size > 0) {
if (is_locked) {
freelist->FreeLocked(free_start, free_size);
} else {
freelist->Free(free_start, free_size);
}
}
}
return result;
}
uword PageSpace::TryAllocateInFreshLargePage(intptr_t size,
OldPage::PageType type,
GrowthPolicy growth_policy) {
ASSERT(!Heap::IsAllocatableViaFreeLists(size));
EvaluateConcurrentMarking(growth_policy);
intptr_t page_size_in_words = LargePageSizeInWordsFor(size);
if ((page_size_in_words << kWordSizeLog2) < size) {
// On overflow we fail to allocate.
return 0;
}
uword result = 0;
SpaceUsage after_allocation = GetCurrentUsage();
after_allocation.used_in_words += size >> kWordSizeLog2;
after_allocation.capacity_in_words += page_size_in_words;
if (growth_policy == kForceGrowth ||
!page_space_controller_.ReachedHardThreshold(after_allocation)) {
OldPage* page = AllocateLargePage(size, type);
if (page != NULL) {
result = page->object_start();
// Note: usage_.capacity_in_words is increased by AllocateLargePage.
usage_.used_in_words += (size >> kWordSizeLog2);
}
}
return result;
}
uword PageSpace::TryAllocateInternal(intptr_t size,
FreeList* freelist,
OldPage::PageType type,
GrowthPolicy growth_policy,
bool is_protected,
bool is_locked) {
ASSERT(size >= kObjectAlignment);
ASSERT(Utils::IsAligned(size, kObjectAlignment));
uword result = 0;
if (Heap::IsAllocatableViaFreeLists(size)) {
if (is_locked) {
result = freelist->TryAllocateLocked(size, is_protected);
} else {
result = freelist->TryAllocate(size, is_protected);
}
if (result == 0) {
result = TryAllocateInFreshPage(size, freelist, type, growth_policy,
is_locked);
// usage_ is updated by the call above.
} else {
usage_.used_in_words += (size >> kWordSizeLog2);
}
} else {
result = TryAllocateInFreshLargePage(size, type, growth_policy);
// usage_ is updated by the call above.
}
ASSERT((result & kObjectAlignmentMask) == kOldObjectAlignmentOffset);
return result;
}
void PageSpace::AcquireLock(FreeList* freelist) {
freelist->mutex()->Lock();
}
void PageSpace::ReleaseLock(FreeList* freelist) {
intptr_t size = freelist->TakeUnaccountedSizeLocked();
usage_.used_in_words += (size >> kWordSizeLog2);
freelist->mutex()->Unlock();
}
class BasePageIterator : ValueObject {
public:
explicit BasePageIterator(const PageSpace* space) : space_(space) {}
OldPage* page() const { return page_; }
bool Done() const { return page_ == NULL; }
void Advance() {
ASSERT(!Done());
page_ = page_->next();
if ((page_ == NULL) && (list_ == kRegular)) {
list_ = kExecutable;
page_ = space_->exec_pages_;
}
if ((page_ == NULL) && (list_ == kExecutable)) {
list_ = kLarge;
page_ = space_->large_pages_;
}
if ((page_ == NULL) && (list_ == kLarge)) {
list_ = kImage;
page_ = space_->image_pages_;
}
ASSERT((page_ != NULL) || (list_ == kImage));
}
protected:
enum List { kRegular, kExecutable, kLarge, kImage };
void Initialize() {
list_ = kRegular;
page_ = space_->pages_;
if (page_ == NULL) {
list_ = kExecutable;
page_ = space_->exec_pages_;
if (page_ == NULL) {
list_ = kLarge;
page_ = space_->large_pages_;
if (page_ == NULL) {
list_ = kImage;
page_ = space_->image_pages_;
}
}
}
}
const PageSpace* space_ = nullptr;
List list_;
OldPage* page_ = nullptr;
};
// Provides unsafe access to all pages. Assumes pages are walkable.
class UnsafeExclusivePageIterator : public BasePageIterator {
public:
explicit UnsafeExclusivePageIterator(const PageSpace* space)
: BasePageIterator(space) {
Initialize();
}
};
// Provides exclusive access to all pages, and ensures they are walkable.
class ExclusivePageIterator : public BasePageIterator {
public:
explicit ExclusivePageIterator(const PageSpace* space)
: BasePageIterator(space), ml_(&space->pages_lock_) {
space_->MakeIterable();
Initialize();
}
private:
MutexLocker ml_;
NoSafepointScope no_safepoint;
};
// Provides exclusive access to code pages, and ensures they are walkable.
// NOTE: This does not iterate over large pages which can contain code.
class ExclusiveCodePageIterator : ValueObject {
public:
explicit ExclusiveCodePageIterator(const PageSpace* space)
: space_(space), ml_(&space->pages_lock_) {
space_->MakeIterable();
page_ = space_->exec_pages_;
}
OldPage* page() const { return page_; }
bool Done() const { return page_ == NULL; }
void Advance() {
ASSERT(!Done());
page_ = page_->next();
}
private:
const PageSpace* space_;
MutexLocker ml_;
NoSafepointScope no_safepoint;
OldPage* page_;
};
void PageSpace::MakeIterable() const {
// Assert not called from concurrent sweeper task.
// TODO(koda): Use thread/task identity when implemented.
ASSERT(IsolateGroup::Current()->heap() != NULL);
for (intptr_t i = 0; i < num_freelists_; i++) {
freelists_[i].MakeIterable();
}
}
void PageSpace::AbandonBumpAllocation() {
for (intptr_t i = 0; i < num_freelists_; i++) {
freelists_[i].AbandonBumpAllocation();
}
}
void PageSpace::AbandonMarkingForShutdown() {
delete marker_;
marker_ = NULL;
}
void PageSpace::UpdateMaxCapacityLocked() {
if (heap_ == NULL) {
// Some unit tests.
return;
}
ASSERT(heap_ != NULL);
ASSERT(heap_->isolate_group() != NULL);
auto isolate_group = heap_->isolate_group();
isolate_group->GetHeapOldCapacityMaxMetric()->SetValue(
static_cast<int64_t>(usage_.capacity_in_words) * kWordSize);
}
void PageSpace::UpdateMaxUsed() {
if (heap_ == NULL) {
// Some unit tests.
return;
}
ASSERT(heap_ != NULL);
ASSERT(heap_->isolate_group() != NULL);
auto isolate_group = heap_->isolate_group();
isolate_group->GetHeapOldUsedMaxMetric()->SetValue(UsedInWords() * kWordSize);
}
bool PageSpace::Contains(uword addr) const {
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if (it.page()->Contains(addr)) {
return true;
}
}
return false;
}
bool PageSpace::ContainsUnsafe(uword addr) const {
for (UnsafeExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if (it.page()->Contains(addr)) {
return true;
}
}
return false;
}
bool PageSpace::Contains(uword addr, OldPage::PageType type) const {
if (type == OldPage::kExecutable) {
// Fast path executable pages.
for (ExclusiveCodePageIterator it(this); !it.Done(); it.Advance()) {
if (it.page()->Contains(addr)) {
return true;
}
}
return false;
}
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if ((it.page()->type() == type) && it.page()->Contains(addr)) {
return true;
}
}
return false;
}
bool PageSpace::DataContains(uword addr) const {
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if ((it.page()->type() != OldPage::kExecutable) &&
it.page()->Contains(addr)) {
return true;
}
}
return false;
}
void PageSpace::AddRegionsToObjectSet(ObjectSet* set) const {
ASSERT((pages_ != NULL) || (exec_pages_ != NULL) || (large_pages_ != NULL));
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
set->AddRegion(it.page()->object_start(), it.page()->object_end());
}
}
void PageSpace::VisitObjects(ObjectVisitor* visitor) const {
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
it.page()->VisitObjects(visitor);
}
}
void PageSpace::VisitObjectsNoImagePages(ObjectVisitor* visitor) const {
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if (!it.page()->is_image_page()) {
it.page()->VisitObjects(visitor);
}
}
}
void PageSpace::VisitObjectsImagePages(ObjectVisitor* visitor) const {
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if (it.page()->is_image_page()) {
it.page()->VisitObjects(visitor);
}
}
}
void PageSpace::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
it.page()->VisitObjectPointers(visitor);
}
}
void PageSpace::VisitRememberedCards(ObjectPointerVisitor* visitor) const {
ASSERT(Thread::Current()->IsAtSafepoint() ||
(Thread::Current()->task_kind() == Thread::kScavengerTask));
// Wait for the sweeper to finish mutating the large page list.
{
MonitorLocker ml(tasks_lock());
while (phase() == kSweepingLarge) {
ml.Wait(); // No safepoint check.
}
}
// Large pages may be added concurrently due to promotion in another scavenge
// worker, so terminate the traversal when we hit the tail we saw while
// holding the pages lock, instead of at NULL, otherwise we are racing when we
// read OldPage::next_ and OldPage::remembered_cards_.
OldPage* page;
OldPage* tail;
{
MutexLocker ml(&pages_lock_);
page = large_pages_;
tail = large_pages_tail_;
}
while (page != nullptr) {
page->VisitRememberedCards(visitor);
if (page == tail) break;
page = page->next();
}
}
ObjectPtr PageSpace::FindObject(FindObjectVisitor* visitor,
OldPage::PageType type) const {
if (type == OldPage::kExecutable) {
// Fast path executable pages.
for (ExclusiveCodePageIterator it(this); !it.Done(); it.Advance()) {
ObjectPtr obj = it.page()->FindObject(visitor);
if (obj != Object::null()) {
return obj;
}
}
return Object::null();
}
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if (it.page()->type() == type) {
ObjectPtr obj = it.page()->FindObject(visitor);
if (obj != Object::null()) {
return obj;
}
}
}
return Object::null();
}
void PageSpace::WriteProtect(bool read_only) {
if (read_only) {
// Avoid MakeIterable trying to write to the heap.
AbandonBumpAllocation();
}
for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
if (!it.page()->is_image_page()) {
it.page()->WriteProtect(read_only);
}
}
}
#ifndef PRODUCT
void PageSpace::PrintToJSONObject(JSONObject* object) const {
auto isolate_group = IsolateGroup::Current();
ASSERT(isolate_group != nullptr);
JSONObject space(object, "old");
space.AddProperty("type", "HeapSpace");
space.AddProperty("name", "old");
space.AddProperty("vmName", "PageSpace");
space.AddProperty("collections", collections());
space.AddProperty64("used", UsedInWords() * kWordSize);
space.AddProperty64("capacity", CapacityInWords() * kWordSize);
space.AddProperty64("external", ExternalInWords() * kWordSize);
space.AddProperty("time", MicrosecondsToSeconds(gc_time_micros()));
if (collections() > 0) {
int64_t run_time = isolate_group->UptimeMicros();
run_time = Utils::Maximum(run_time, static_cast<int64_t>(0));
double run_time_millis = MicrosecondsToMilliseconds(run_time);
double avg_time_between_collections =
run_time_millis / static_cast<double>(collections());
space.AddProperty("avgCollectionPeriodMillis",
avg_time_between_collections);
} else {
space.AddProperty("avgCollectionPeriodMillis", 0.0);
}
}
class HeapMapAsJSONVisitor : public ObjectVisitor {
public:
explicit HeapMapAsJSONVisitor(JSONArray* array) : array_(array) {}
virtual void VisitObject(ObjectPtr obj) {
array_->AddValue(obj->untag()->HeapSize() / kObjectAlignment);
array_->AddValue(obj->GetClassId());
}
private:
JSONArray* array_;
};
void PageSpace::PrintHeapMapToJSONStream(IsolateGroup* isolate_group,
JSONStream* stream) const {
JSONObject heap_map(stream);
heap_map.AddProperty("type", "HeapMap");
heap_map.AddProperty("freeClassId", static_cast<intptr_t>(kFreeListElement));
heap_map.AddProperty("unitSizeBytes",
static_cast<intptr_t>(kObjectAlignment));
heap_map.AddProperty("pageSizeBytes", kOldPageSizeInWords * kWordSize);
{
JSONObject class_list(&heap_map, "classList");
isolate_group->class_table()->PrintToJSONObject(&class_list);
}
{
// "pages" is an array [page0, page1, ..., pageN], each page of the form
// {"object_start": "0x...", "objects": [size, class id, size, ...]}
// TODO(19445): Use ExclusivePageIterator once HeapMap supports large pages.
HeapIterationScope iteration(Thread::Current());
MutexLocker ml(&pages_lock_);
MakeIterable();
JSONArray all_pages(&heap_map, "pages");
for (OldPage* page = pages_; page != NULL; page = page->next()) {
JSONObject page_container(&all_pages);
page_container.AddPropertyF("objectStart", "0x%" Px "",
page->object_start());
JSONArray page_map(&page_container, "objects");
HeapMapAsJSONVisitor printer(&page_map);
page->VisitObjects(&printer);
}
for (OldPage* page = exec_pages_; page != NULL; page = page->next()) {
JSONObject page_container(&all_pages);
page_container.AddPropertyF("objectStart", "0x%" Px "",
page->object_start());
JSONArray page_map(&page_container, "objects");
HeapMapAsJSONVisitor printer(&page_map);
page->VisitObjects(&printer);
}
}
}
#endif // PRODUCT
void PageSpace::WriteProtectCode(bool read_only) {
if (FLAG_write_protect_code) {
MutexLocker ml(&pages_lock_);
NoSafepointScope no_safepoint;
// No need to go through all of the data pages first.
OldPage* page = exec_pages_;
while (page != NULL) {
ASSERT(page->type() == OldPage::kExecutable);
page->WriteProtect(read_only);
page = page->next();
}
page = large_pages_;
while (page != NULL) {
if (page->type() == OldPage::kExecutable) {
page->WriteProtect(read_only);
}
page = page->next();
}
}
}
bool PageSpace::ShouldStartIdleMarkSweep(int64_t deadline) {
// To make a consistent decision, we should not yield for a safepoint in the
// middle of deciding whether to perform an idle GC.
NoSafepointScope no_safepoint;
if (!page_space_controller_.ReachedIdleThreshold(usage_)) {
return false;
}
{
MonitorLocker locker(tasks_lock());
if (tasks() > 0) {
// A concurrent sweeper is running. If we start a mark sweep now
// we'll have to wait for it, and this wait time is not included in
// mark_words_per_micro_.
return false;
}
}
// This uses the size of new-space because the pause time to start concurrent
// marking is related to the size of the root set, which is mostly new-space.
int64_t estimated_mark_completion =
OS::GetCurrentMonotonicMicros() +
heap_->new_space()->UsedInWords() / mark_words_per_micro_;
return estimated_mark_completion <= deadline;
}
bool PageSpace::ShouldPerformIdleMarkCompact(int64_t deadline) {
// To make a consistent decision, we should not yield for a safepoint in the
// middle of deciding whether to perform an idle GC.
NoSafepointScope no_safepoint;
// Discount two pages to account for the newest data and code pages, whose
// partial use doesn't indicate fragmentation.
const intptr_t excess_in_words =
usage_.capacity_in_words - usage_.used_in_words - 2 * kOldPageSizeInWords;
const double excess_ratio = static_cast<double>(excess_in_words) /
static_cast<double>(usage_.capacity_in_words);
const bool fragmented = excess_ratio > 0.05;
if (!fragmented && !page_space_controller_.ReachedIdleThreshold(usage_)) {
return false;
}
{
MonitorLocker locker(tasks_lock());
if (tasks() > 0) {
// A concurrent sweeper is running. If we start a mark sweep now
// we'll have to wait for it, and this wait time is not included in
// mark_words_per_micro_.
return false;
}
}
// Assuming compaction takes as long as marking.
intptr_t mark_compact_words_per_micro = mark_words_per_micro_ / 2;
if (mark_compact_words_per_micro == 0) {
mark_compact_words_per_micro = 1; // Prevent division by zero.
}
int64_t estimated_mark_compact_completion =
OS::GetCurrentMonotonicMicros() +
UsedInWords() / mark_compact_words_per_micro;
return estimated_mark_compact_completion <= deadline;
}
void PageSpace::TryReleaseReservation() {
if (oom_reservation_ == nullptr) return;
uword addr = reinterpret_cast<uword>(oom_reservation_);
intptr_t size = oom_reservation_->HeapSize();
oom_reservation_ = nullptr;
freelists_[OldPage::kData].Free(addr, size);
}
bool PageSpace::MarkReservation() {
if (oom_reservation_ == nullptr) {
return false;
}
UntaggedObject* ptr = reinterpret_cast<UntaggedObject*>(oom_reservation_);
if (!ptr->IsMarked()) {
ptr->SetMarkBit();
}
return true;
}
void PageSpace::TryReserveForOOM() {
if (oom_reservation_ == nullptr) {
uword addr = TryAllocate(kOOMReservationSize, OldPage::kData,
kForceGrowth /* Don't re-enter GC */);
if (addr != 0) {
oom_reservation_ = FreeListElement::AsElement(addr, kOOMReservationSize);
}
}
}
void PageSpace::VisitRoots(ObjectPointerVisitor* visitor) {
if (oom_reservation_ != nullptr) {
// FreeListElements are generally held untagged, but ObjectPointerVisitors
// expect tagged pointers.
ObjectPtr ptr =
UntaggedObject::FromAddr(reinterpret_cast<uword>(oom_reservation_));
visitor->VisitPointer(&ptr);
oom_reservation_ =
reinterpret_cast<FreeListElement*>(UntaggedObject::ToAddr(ptr));
}
}
void PageSpace::CollectGarbage(bool compact, bool finalize) {
ASSERT(GrowthControlState());
if (!finalize) {
#if defined(TARGET_ARCH_IA32)
return; // Barrier not implemented.
#else
if (!enable_concurrent_mark()) return; // Disabled.
if (FLAG_marker_tasks == 0) return; // Disabled.
#endif
}
Thread* thread = Thread::Current();
const int64_t pre_safe_point = OS::GetCurrentMonotonicMicros();
SafepointOperationScope safepoint_scope(thread);
const int64_t pre_wait_for_sweepers = OS::GetCurrentMonotonicMicros();
// Wait for pending tasks to complete and then account for the driver task.
Phase waited_for;
{
MonitorLocker locker(tasks_lock());
waited_for = phase();
if (!finalize &&
(phase() == kMarking || phase() == kAwaitingFinalization)) {
// Concurrent mark is already running.
return;
}
while (tasks() > 0) {
locker.Wait();
}
ASSERT(phase() == kAwaitingFinalization || phase() == kDone);
set_tasks(1);
}
if (FLAG_verbose_gc) {
const int64_t wait =
OS::GetCurrentMonotonicMicros() - pre_wait_for_sweepers;
if (waited_for == kMarking) {
THR_Print("Waited %" Pd64 " us for concurrent marking to finish.\n",
wait);
} else if (waited_for == kSweepingRegular || waited_for == kSweepingLarge) {
THR_Print("Waited %" Pd64 " us for concurrent sweeping to finish.\n",
wait);
}
}
// Ensure that all threads for this isolate are at a safepoint (either
// stopped or in native code). We have guards around Newgen GC and oldgen GC
// to ensure that if two threads are racing to collect at the same time the
// loser skips collection and goes straight to allocation.
{
CollectGarbageHelper(compact, finalize, pre_wait_for_sweepers,
pre_safe_point);
}
// Done, reset the task count.
{
MonitorLocker ml(tasks_lock());
set_tasks(tasks() - 1);
ml.NotifyAll();
}
}
void PageSpace::CollectGarbageHelper(bool compact,
bool finalize,
int64_t pre_wait_for_sweepers,
int64_t pre_safe_point) {
Thread* thread = Thread::Current();
ASSERT(thread->IsAtSafepoint());
auto isolate_group = heap_->isolate_group();
ASSERT(isolate_group == IsolateGroup::Current());
const int64_t start = OS::GetCurrentMonotonicMicros();
// Perform various cleanup that relies on no tasks interfering.
isolate_group->shared_class_table()->FreeOldTables();
isolate_group->ForEachIsolate(
[&](Isolate* isolate) { isolate->field_table()->FreeOldTables(); },
/*at_safepoint=*/true);
NoSafepointScope no_safepoints;
if (FLAG_print_free_list_before_gc) {
for (intptr_t i = 0; i < num_freelists_; i++) {
OS::PrintErr("Before GC: Freelist %" Pd "\n", i);
freelists_[i].Print();
}
}
if (FLAG_verify_before_gc) {
OS::PrintErr("Verifying before marking...");
heap_->VerifyGC(phase() == kDone ? kForbidMarked : kAllowMarked);
OS::PrintErr(" done.\n");
}
// Make code pages writable.
if (finalize) WriteProtectCode(false);
// Save old value before GCMarker visits the weak persistent handles.
SpaceUsage usage_before = GetCurrentUsage();
// Mark all reachable old-gen objects.
if (marker_ == NULL) {
ASSERT(phase() == kDone);
marker_ = new GCMarker(isolate_group, heap_);
} else {
ASSERT(phase() == kAwaitingFinalization);
}
if (!finalize) {
ASSERT(phase() == kDone);
marker_->StartConcurrentMark(this);
return;
}
marker_->MarkObjects(this);
usage_.used_in_words = marker_->marked_words() + allocated_black_in_words_;
allocated_black_in_words_ = 0;
mark_words_per_micro_ = marker_->MarkedWordsPerMicro();
delete marker_;
marker_ = NULL;
int64_t mid1 = OS::GetCurrentMonotonicMicros();
// Abandon the remainder of the bump allocation block.
AbandonBumpAllocation();
// Reset the freelists and setup sweeping.
for (intptr_t i = 0; i < num_freelists_; i++) {
freelists_[i].Reset();
}
int64_t mid2 = OS::GetCurrentMonotonicMicros();
int64_t mid3 = 0;
{
if (FLAG_verify_before_gc) {
OS::PrintErr("Verifying before sweeping...");
heap_->VerifyGC(kAllowMarked);
OS::PrintErr(" done.\n");
}
// Executable pages are always swept immediately to simplify
// code protection.
TIMELINE_FUNCTION_GC_DURATION(thread, "SweepExecutable");
GCSweeper sweeper;
OldPage* prev_page = NULL;
OldPage* page = exec_pages_;
FreeList* freelist = &freelists_[OldPage::kExecutable];
MutexLocker ml(freelist->mutex());
while (page != NULL) {
OldPage* next_page = page->next();
bool page_in_use = sweeper.SweepPage(page, freelist, true /*is_locked*/);
if (page_in_use) {
prev_page = page;
} else {
FreePage(page, prev_page);
}
// Advance to the next page.
page = next_page;
}
mid3 = OS::GetCurrentMonotonicMicros();
}
bool has_reservation = MarkReservation();
if (compact) {
SweepLarge();
Compact(thread);
set_phase(kDone);
} else if (FLAG_concurrent_sweep && has_reservation) {
ConcurrentSweep(isolate_group);
} else {
SweepLarge();
Sweep();
set_phase(kDone);
}
TryReserveForOOM();
// Make code pages read-only.
if (finalize) WriteProtectCode(true);
int64_t end = OS::GetCurrentMonotonicMicros();
// Record signals for growth control. Include size of external allocations.
page_space_controller_.EvaluateGarbageCollection(
usage_before, GetCurrentUsage(), start, end);
heap_->RecordTime(kConcurrentSweep, pre_safe_point - pre_wait_for_sweepers);
heap_->RecordTime(kSafePoint, start - pre_safe_point);
heap_->RecordTime(kMarkObjects, mid1 - start);
heap_->RecordTime(kResetFreeLists, mid2 - mid1);
heap_->RecordTime(kSweepPages, mid3 - mid2);
heap_->RecordTime(kSweepLargePages, end - mid3);
if (FLAG_print_free_list_after_gc) {
for (intptr_t i = 0; i < num_freelists_; i++) {
OS::PrintErr("After GC: Freelist %" Pd "\n", i);
freelists_[i].Print();
}
}
UpdateMaxUsed();
if (heap_ != NULL) {
heap_->UpdateGlobalMaxUsed();
}
}
void PageSpace::SweepLarge() {
TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "SweepLarge");
GCSweeper sweeper;
OldPage* prev_page = nullptr;
OldPage* page = large_pages_;
while (page != nullptr) {
OldPage* next_page = page->next();
const intptr_t words_to_end = sweeper.SweepLargePage(page);
if (words_to_end == 0) {
FreeLargePage(page, prev_page);
} else {
TruncateLargePage(page, words_to_end << kWordSizeLog2);
prev_page = page;
}
// Advance to the next page.
page = next_page;
}
}
void PageSpace::Sweep() {
TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "Sweep");
GCSweeper sweeper;
intptr_t shard = 0;
const intptr_t num_shards = Utils::Maximum(FLAG_scavenger_tasks, 1);
for (intptr_t i = 0; i < num_shards; i++) {
DataFreeList(i)->mutex()->Lock();
}
OldPage* prev_page = nullptr;
OldPage* page = pages_;
while (page != nullptr) {
OldPage* next_page = page->next();
ASSERT(page->type() == OldPage::kData);
shard = (shard + 1) % num_shards;
bool page_in_use =
sweeper.SweepPage(page, DataFreeList(shard), true /*is_locked*/);
if (page_in_use) {
prev_page = page;
} else {
FreePage(page, prev_page);
}
// Advance to the next page.
page = next_page;
}
for (intptr_t i = 0; i < num_shards; i++) {
DataFreeList(i)->mutex()->Unlock();
}
if (FLAG_verify_after_gc) {
OS::PrintErr("Verifying after sweeping...");
heap_->VerifyGC(kForbidMarked);
OS::PrintErr(" done.\n");
}
}
void PageSpace::ConcurrentSweep(IsolateGroup* isolate_group) {
// Start the concurrent sweeper task now.
GCSweeper::SweepConcurrent(isolate_group, pages_, pages_tail_, large_pages_,
large_pages_tail_, &freelists_[OldPage::kData]);
}
void PageSpace::Compact(Thread* thread) {
thread->isolate_group()->set_compaction_in_progress(true);
GCCompactor compactor(thread, heap_);
compactor.Compact(pages_, &freelists_[OldPage::kData], &pages_lock_);
thread->isolate_group()->set_compaction_in_progress(false);
if (FLAG_verify_after_gc) {
OS::PrintErr("Verifying after compacting...");
heap_->VerifyGC(kForbidMarked);
OS::PrintErr(" done.\n");
}
}
uword PageSpace::TryAllocateDataBumpLocked(FreeList* freelist, intptr_t size) {
ASSERT(size >= kObjectAlignment);
ASSERT(Utils::IsAligned(size, kObjectAlignment));
intptr_t remaining = freelist->end() - freelist->top();
if (UNLIKELY(remaining < size)) {
// Checking this first would be logical, but needlessly slow.
if (!Heap::IsAllocatableViaFreeLists(size)) {
return TryAllocateDataLocked(freelist, size, kForceGrowth);
}
FreeListElement* block = freelist->TryAllocateLargeLocked(size);
if (block == NULL) {
// Allocating from a new page (if growth policy allows) will have the
// side-effect of populating the freelist with a large block. The next
// bump allocation request will have a chance to consume that block.
// TODO(koda): Could take freelist lock just once instead of twice.
return TryAllocateInFreshPage(size, freelist, OldPage::kData,
kForceGrowth, true /* is_locked*/);
}
intptr_t block_size = block->HeapSize();
if (remaining > 0) {
freelist->FreeLocked(freelist->top(), remaining);
}
freelist->set_top(reinterpret_cast<uword>(block));
freelist->set_end(freelist->top() + block_size);
remaining = block_size;
}
ASSERT(remaining >= size);
uword result = freelist->top();
freelist->set_top(result + size);
freelist->AddUnaccountedSize(size);
// Note: Remaining block is unwalkable until MakeIterable is called.
#ifdef DEBUG
if (freelist->top() < freelist->end()) {
// Fail fast if we try to walk the remaining block.
COMPILE_ASSERT(kIllegalCid == 0);
*reinterpret_cast<uword*>(freelist->top()) = 0;
}
#endif // DEBUG
return result;
}
uword PageSpace::TryAllocatePromoLockedSlow(FreeList* freelist, intptr_t size) {
uword result = freelist->TryAllocateSmallLocked(size);
if (result != 0) {
freelist->AddUnaccountedSize(size);
return result;
}
return TryAllocateDataBumpLocked(freelist, size);
}
void PageSpace::SetupImagePage(void* pointer, uword size, bool is_executable) {
// Setup a OldPage so precompiled Instructions can be traversed.
// Instructions are contiguous at [pointer, pointer + size). OldPage
// expects to find objects at [memory->start() + ObjectStartOffset,
// memory->end()).
uword offset = OldPage::ObjectStartOffset();
pointer = reinterpret_cast<void*>(reinterpret_cast<uword>(pointer) - offset);
ASSERT(Utils::IsAligned(pointer, kObjectAlignment));
size += offset;
VirtualMemory* memory = VirtualMemory::ForImagePage(pointer, size);
ASSERT(memory != NULL);
OldPage* page = reinterpret_cast<OldPage*>(malloc(sizeof(OldPage)));
page->memory_ = memory;
page->next_ = NULL;
page->object_end_ = memory->end();
page->used_in_bytes_ = page->object_end_ - page->object_start();
page->forwarding_page_ = NULL;
page->card_table_ = NULL;
if (is_executable) {
page->type_ = OldPage::kExecutable;
} else {
page->type_ = OldPage::kData;
}
MutexLocker ml(&pages_lock_);
page->next_ = image_pages_;
image_pages_ = page;
}
bool PageSpace::IsObjectFromImagePages(dart::ObjectPtr object) {
uword object_addr = UntaggedObject::ToAddr(object);
OldPage* image_page = image_pages_;
while (image_page != nullptr) {
if (image_page->Contains(object_addr)) {
return true;
}
image_page = image_page->next();
}
return false;
}
PageSpaceController::PageSpaceController(Heap* heap,
int heap_growth_ratio,
int heap_growth_max,
int garbage_collection_time_ratio)
: heap_(heap),
is_enabled_(false),
heap_growth_ratio_(heap_growth_ratio),
desired_utilization_((100.0 - heap_growth_ratio) / 100.0),
heap_growth_max_(heap_growth_max),
garbage_collection_time_ratio_(garbage_collection_time_ratio),
idle_gc_threshold_in_words_(0) {
const intptr_t growth_in_pages = heap_growth_max / 2;
RecordUpdate(last_usage_, last_usage_, growth_in_pages, "initial");
}
PageSpaceController::~PageSpaceController() {}
bool PageSpaceController::ReachedHardThreshold(SpaceUsage after) const {
if (!is_enabled_) {
return false;
}
if (heap_growth_ratio_ == 100) {
return false;
}
return after.CombinedUsedInWords() > hard_gc_threshold_in_words_;
}
bool PageSpaceController::ReachedSoftThreshold(SpaceUsage after) const {
if (!is_enabled_) {
return false;
}
if (heap_growth_ratio_ == 100) {
return false;
}
return after.CombinedUsedInWords() > soft_gc_threshold_in_words_;
}
bool PageSpaceController::ReachedIdleThreshold(SpaceUsage current) const {
if (!is_enabled_) {
return false;
}
if (heap_growth_ratio_ == 100) {
return false;
}
return current.CombinedUsedInWords() > idle_gc_threshold_in_words_;
}
void PageSpaceController::EvaluateGarbageCollection(SpaceUsage before,
SpaceUsage after,
int64_t start,
int64_t end) {
ASSERT(end >= start);
history_.AddGarbageCollectionTime(start, end);
const int gc_time_fraction = history_.GarbageCollectionTimeFraction();
heap_->RecordData(PageSpace::kGCTimeFraction, gc_time_fraction);
// Assume garbage increases linearly with allocation:
// G = kA, and estimate k from the previous cycle.
const intptr_t allocated_since_previous_gc =
before.CombinedUsedInWords() - last_usage_.CombinedUsedInWords();
intptr_t grow_heap;
if (allocated_since_previous_gc > 0) {
intptr_t garbage =
before.CombinedUsedInWords() - after.CombinedUsedInWords();
// Garbage may be negative if when the OOM reservation is refilled.
garbage = Utils::Maximum(static_cast<intptr_t>(0), garbage);
// It makes no sense to expect that each kb allocated will cause more than
// one kb of garbage, so we clamp k at 1.0.
const double k = Utils::Minimum(
1.0, garbage / static_cast<double>(allocated_since_previous_gc));
const int garbage_ratio = static_cast<int>(k * 100);
heap_->RecordData(PageSpace::kGarbageRatio, garbage_ratio);
// Define GC to be 'worthwhile' iff at least fraction t of heap is garbage.
double t = 1.0 - desired_utilization_;
// If we spend too much time in GC, strive for even more free space.
if (gc_time_fraction > garbage_collection_time_ratio_) {
t += (gc_time_fraction - garbage_collection_time_ratio_) / 100.0;
}
// Number of pages we can allocate and still be within the desired growth
// ratio.
const intptr_t grow_pages =
(static_cast<intptr_t>(after.CombinedUsedInWords() /
desired_utilization_) -
(after.CombinedUsedInWords())) /
kOldPageSizeInWords;
if (garbage_ratio == 0) {
// No garbage in the previous cycle so it would be hard to compute a
// grow_heap size based on estimated garbage so we use growth ratio
// heuristics instead.
grow_heap =
Utils::Maximum(static_cast<intptr_t>(heap_growth_max_), grow_pages);
} else {
// Find minimum 'grow_heap' such that after increasing capacity by
// 'grow_heap' pages and filling them, we expect a GC to be worthwhile.
intptr_t max = heap_growth_max_;
intptr_t min = 0;
intptr_t local_grow_heap = 0;
while (min < max) {
local_grow_heap = (max + min) / 2;
const intptr_t limit = after.CombinedUsedInWords() +
(local_grow_heap * kOldPageSizeInWords);
const intptr_t allocated_before_next_gc =
limit - (after.CombinedUsedInWords());
const double estimated_garbage = k * allocated_before_next_gc;
if (t <= estimated_garbage / limit) {
max = local_grow_heap - 1;
} else {
min = local_grow_heap + 1;
}
}
local_grow_heap = (max + min) / 2;
grow_heap = local_grow_heap;
ASSERT(grow_heap >= 0);
// If we are going to grow by heap_grow_max_ then ensure that we
// will be growing the heap at least by the growth ratio heuristics.
if (grow_heap >= heap_growth_max_) {
grow_heap = Utils::Maximum(grow_pages, grow_heap);
}
}
} else {
heap_->RecordData(PageSpace::kGarbageRatio, 100);
grow_heap = 0;
}
heap_->RecordData(PageSpace::kPageGrowth, grow_heap);
last_usage_ = after;
intptr_t max_capacity_in_words = heap_->old_space()->max_capacity_in_words_;
if (max_capacity_in_words != 0) {
ASSERT(grow_heap >= 0);
// Fraction of asymptote used.
double f = static_cast<double>(after.CombinedUsedInWords() +
(kOldPageSizeInWords * grow_heap)) /
static_cast<double>(max_capacity_in_words);
ASSERT(f >= 0.0);
// Increase weight at the high end.
f = f * f;
// Fraction of asymptote available.
f = 1.0 - f;
ASSERT(f <= 1.0);
// Discount growth more the closer we get to the desired asymptote.
grow_heap = static_cast<intptr_t>(grow_heap * f);
// Minimum growth step after reaching the asymptote.
intptr_t min_step = (2 * MB) / kOldPageSize;
grow_heap = Utils::Maximum(min_step, grow_heap);
}
RecordUpdate(before, after, grow_heap, "gc");
}
void PageSpaceController::EvaluateAfterLoading(SpaceUsage after) {
// Number of pages we can allocate and still be within the desired growth
// ratio.
intptr_t growth_in_pages;
if (desired_utilization_ == 0.0) {
growth_in_pages = heap_growth_max_;
} else {
growth_in_pages = (static_cast<intptr_t>(after.CombinedUsedInWords() /
desired_utilization_) -
(after.CombinedUsedInWords())) /
kOldPageSizeInWords;
}
// Apply growth cap.
growth_in_pages =
Utils::Minimum(static_cast<intptr_t>(heap_growth_max_), growth_in_pages);
RecordUpdate(after, after, growth_in_pages, "loaded");
}
void PageSpaceController::RecordUpdate(SpaceUsage before,
SpaceUsage after,
intptr_t growth_in_pages,
const char* reason) {
// Save final threshold compared before growing.
hard_gc_threshold_in_words_ =
after.CombinedUsedInWords() + (kOldPageSizeInWords * growth_in_pages);
// Start concurrent marking when old-space has less than half of new-space
// available or less than 5% available.
#if defined(TARGET_ARCH_IA32)
const intptr_t headroom = 0; // No concurrent marking.
#else
// Note that heap_ can be null in some unit tests.
const intptr_t new_space =
heap_ == nullptr ? 0 : heap_->new_space()->CapacityInWords();
const intptr_t headroom =
Utils::Maximum(new_space / 2, hard_gc_threshold_in_words_ / 20);
#endif
soft_gc_threshold_in_words_ = hard_gc_threshold_in_words_ - headroom;
// Set a tight idle threshold.
idle_gc_threshold_in_words_ =
after.CombinedUsedInWords() + (2 * kOldPageSizeInWords);
#if defined(SUPPORT_TIMELINE)
Thread* thread = Thread::Current();
if (thread != nullptr) {
TIMELINE_FUNCTION_GC_DURATION(thread, "UpdateGrowthLimit");
tbes.SetNumArguments(6);
tbes.CopyArgument(0, "Reason", reason);
tbes.FormatArgument(1, "Before.CombinedUsed (kB)", "%" Pd "",
RoundWordsToKB(before.CombinedUsedInWords()));
tbes.FormatArgument(2, "After.CombinedUsed (kB)", "%" Pd "",
RoundWordsToKB(after.CombinedUsedInWords()));
tbes.FormatArgument(3, "Hard Threshold (kB)", "%" Pd "",
RoundWordsToKB(hard_gc_threshold_in_words_));
tbes.FormatArgument(4, "Soft Threshold (kB)", "%" Pd "",
RoundWordsToKB(soft_gc_threshold_in_words_));
tbes.FormatArgument(5, "Idle Threshold (kB)", "%" Pd "",
RoundWordsToKB(idle_gc_threshold_in_words_));
}
#endif
if (FLAG_log_growth) {
THR_Print("%s: threshold=%" Pd "kB, idle_threshold=%" Pd "kB, reason=%s\n",
heap_->isolate_group()->source()->name,
hard_gc_threshold_in_words_ / KBInWords,
idle_gc_threshold_in_words_ / KBInWords, reason);
}
}
void PageSpaceController::HintFreed(intptr_t size) {
intptr_t size_in_words = size << kWordSizeLog2;
if (size_in_words > idle_gc_threshold_in_words_) {
idle_gc_threshold_in_words_ = 0;
} else {
idle_gc_threshold_in_words_ -= size_in_words;
}
// TODO(rmacnak): Hasten the soft threshold at some discount?
}
void PageSpaceGarbageCollectionHistory::AddGarbageCollectionTime(int64_t start,
int64_t end) {
Entry entry;
entry.start = start;
entry.end = end;
history_.Add(entry);
}
int PageSpaceGarbageCollectionHistory::GarbageCollectionTimeFraction() {
int64_t gc_time = 0;
int64_t total_time = 0;
for (int i = 0; i < history_.Size() - 1; i++) {
Entry current = history_.Get(i);
Entry previous = history_.Get(i + 1);
gc_time += current.end - current.start;
total_time += current.end - previous.end;
}
if (total_time == 0) {
return 0;
} else {
ASSERT(total_time >= gc_time);
int result = static_cast<int>(
(static_cast<double>(gc_time) / static_cast<double>(total_time)) * 100);
return result;
}
}
} // namespace dart
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