// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/heap/memory-reducer.h"
#include "src/flags.h"
#include "src/heap/gc-tracer.h"
#include "src/heap/heap-inl.h"
#include "src/utils.h"
#include "src/v8.h"
namespace v8 {
namespace internal {
const int MemoryReducer::kLongDelayMs = 8000;
const int MemoryReducer::kShortDelayMs = 500;
const int MemoryReducer::kWatchdogDelayMs = 100000;
const int MemoryReducer::kMaxNumberOfGCs = 3;
const double MemoryReducer::kCommittedMemoryFactor = 1.1;
const size_t MemoryReducer::kCommittedMemoryDelta = 10 * MB;
MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
: CancelableTask(memory_reducer->heap()->isolate()),
memory_reducer_(memory_reducer) {}
void MemoryReducer::TimerTask::RunInternal() {
Heap* heap = memory_reducer_->heap();
Event event;
double time_ms = heap->MonotonicallyIncreasingTimeInMs();
heap->tracer()->SampleAllocation(time_ms, heap->NewSpaceAllocationCounter(),
heap->OldGenerationAllocationCounter());
bool low_allocation_rate = heap->HasLowAllocationRate();
bool optimize_for_memory = heap->ShouldOptimizeForMemoryUsage();
if (FLAG_trace_gc_verbose) {
heap->isolate()->PrintWithTimestamp(
"Memory reducer: %s, %s\n",
low_allocation_rate ? "low alloc" : "high alloc",
optimize_for_memory ? "background" : "foreground");
}
event.type = kTimer;
event.time_ms = time_ms;
// The memory reducer will start incremental markig if
// 1) mutator is likely idle: js call rate is low and allocation rate is low.
// 2) mutator is in background: optimize for memory flag is set.
event.should_start_incremental_gc =
low_allocation_rate || optimize_for_memory;
event.can_start_incremental_gc =
heap->incremental_marking()->IsStopped() &&
(heap->incremental_marking()->CanBeActivated() || optimize_for_memory);
event.committed_memory = heap->CommittedOldGenerationMemory();
memory_reducer_->NotifyTimer(event);
}
void MemoryReducer::NotifyTimer(const Event& event) {
DCHECK_EQ(kTimer, event.type);
DCHECK_EQ(kWait, state_.action);
state_ = Step(state_, event);
if (state_.action == kRun) {
DCHECK(heap()->incremental_marking()->IsStopped());
DCHECK(FLAG_incremental_marking);
if (FLAG_trace_gc_verbose) {
heap()->isolate()->PrintWithTimestamp("Memory reducer: started GC #%d\n",
state_.started_gcs);
}
heap()->StartIdleIncrementalMarking(
GarbageCollectionReason::kMemoryReducer);
} else if (state_.action == kWait) {
if (!heap()->incremental_marking()->IsStopped() &&
heap()->ShouldOptimizeForMemoryUsage()) {
// Make progress with pending incremental marking if memory usage has
// higher priority than latency. This is important for background tabs
// that do not send idle notifications.
const int kIncrementalMarkingDelayMs = 500;
double deadline = heap()->MonotonicallyIncreasingTimeInMs() +
kIncrementalMarkingDelayMs;
heap()->incremental_marking()->AdvanceIncrementalMarking(
deadline, IncrementalMarking::NO_GC_VIA_STACK_GUARD,
IncrementalMarking::FORCE_COMPLETION, StepOrigin::kTask);
heap()->FinalizeIncrementalMarkingIfComplete(
GarbageCollectionReason::kFinalizeMarkingViaTask);
}
// Re-schedule the timer.
ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
if (FLAG_trace_gc_verbose) {
heap()->isolate()->PrintWithTimestamp(
"Memory reducer: waiting for %.f ms\n",
state_.next_gc_start_ms - event.time_ms);
}
}
}
void MemoryReducer::NotifyMarkCompact(const Event& event) {
DCHECK_EQ(kMarkCompact, event.type);
Action old_action = state_.action;
state_ = Step(state_, event);
if (old_action != kWait && state_.action == kWait) {
// If we are transitioning to the WAIT state, start the timer.
ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
}
if (old_action == kRun) {
if (FLAG_trace_gc_verbose) {
heap()->isolate()->PrintWithTimestamp(
"Memory reducer: finished GC #%d (%s)\n", state_.started_gcs,
state_.action == kWait ? "will do more" : "done");
}
}
}
void MemoryReducer::NotifyPossibleGarbage(const Event& event) {
DCHECK_EQ(kPossibleGarbage, event.type);
Action old_action = state_.action;
state_ = Step(state_, event);
if (old_action != kWait && state_.action == kWait) {
// If we are transitioning to the WAIT state, start the timer.
ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
}
}
bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
return state.last_gc_time_ms != 0 &&
event.time_ms > state.last_gc_time_ms + kWatchdogDelayMs;
}
// For specification of this function see the comment for MemoryReducer class.
MemoryReducer::State MemoryReducer::Step(const State& state,
const Event& event) {
if (!FLAG_incremental_marking || !FLAG_memory_reducer) {
return State(kDone, 0, 0, state.last_gc_time_ms, 0);
}
switch (state.action) {
case kDone:
if (event.type == kTimer) {
return state;
} else if (event.type == kMarkCompact) {
if (event.committed_memory <
Max(static_cast<size_t>(state.committed_memory_at_last_run *
kCommittedMemoryFactor),
state.committed_memory_at_last_run + kCommittedMemoryDelta)) {
return state;
} else {
return State(kWait, 0, event.time_ms + kLongDelayMs,
event.type == kMarkCompact ? event.time_ms
: state.last_gc_time_ms,
0);
}
} else {
DCHECK_EQ(kPossibleGarbage, event.type);
return State(
kWait, 0, event.time_ms + kLongDelayMs,
event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms,
0);
}
case kWait:
switch (event.type) {
case kPossibleGarbage:
return state;
case kTimer:
if (state.started_gcs >= kMaxNumberOfGCs) {
return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms,
event.committed_memory);
} else if (event.can_start_incremental_gc &&
(event.should_start_incremental_gc ||
WatchdogGC(state, event))) {
if (state.next_gc_start_ms <= event.time_ms) {
return State(kRun, state.started_gcs + 1, 0.0,
state.last_gc_time_ms, 0);
} else {
return state;
}
} else {
return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
state.last_gc_time_ms, 0);
}
case kMarkCompact:
return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
event.time_ms, 0);
}
case kRun:
if (event.type != kMarkCompact) {
return state;
} else {
if (state.started_gcs < kMaxNumberOfGCs &&
(event.next_gc_likely_to_collect_more || state.started_gcs == 1)) {
return State(kWait, state.started_gcs, event.time_ms + kShortDelayMs,
event.time_ms, 0);
} else {
return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms,
event.committed_memory);
}
}
}
UNREACHABLE();
return State(kDone, 0, 0, 0.0, 0); // Make the compiler happy.
}
void MemoryReducer::ScheduleTimer(double time_ms, double delay_ms) {
DCHECK(delay_ms > 0);
// Leave some room for precision error in task scheduler.
const double kSlackMs = 100;
v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap()->isolate());
auto timer_task = new MemoryReducer::TimerTask(this);
V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
isolate, timer_task, (delay_ms + kSlackMs) / 1000.0);
}
void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0, 0); }
} // namespace internal
} // namespace v8