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// 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 = 5000;
const int MemoryReducer::kShortDelayMs = 500;
const int MemoryReducer::kWatchdogDelayMs = 100000;
const int MemoryReducer::kMaxNumberOfGCs = 3;
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());
event.type = kTimer;
event.time_ms = time_ms;
event.low_allocation_rate = heap->HasLowAllocationRate();
event.can_start_incremental_gc =
heap->incremental_marking()->IsStopped() &&
heap->incremental_marking()->CanBeActivated();
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) {
PrintIsolate(heap()->isolate(), "Memory reducer: started GC #%d\n",
state_.started_gcs);
}
if (heap()->ShouldOptimizeForMemoryUsage()) {
// Do full GC if memory usage has higher priority than latency. This is
// important for background tabs that do not send idle notifications.
heap()->CollectAllGarbage(Heap::kReduceMemoryFootprintMask,
"memory reducer");
} else {
heap()->StartIdleIncrementalMarking();
}
} 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(
0, deadline, i::IncrementalMarking::StepActions(
i::IncrementalMarking::NO_GC_VIA_STACK_GUARD,
i::IncrementalMarking::FORCE_MARKING,
i::IncrementalMarking::FORCE_COMPLETION));
heap()->FinalizeIncrementalMarkingIfComplete(
"Memory reducer: finalize incremental marking");
}
// Re-schedule the timer.
ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
if (FLAG_trace_gc_verbose) {
PrintIsolate(heap()->isolate(), "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(state_.next_gc_start_ms - event.time_ms);
}
if (old_action == kRun) {
if (FLAG_trace_gc_verbose) {
PrintIsolate(heap()->isolate(), "Memory reducer: finished GC #%d (%s)\n",
state_.started_gcs,
state_.action == kWait ? "will do more" : "done");
}
}
}
void MemoryReducer::NotifyContextDisposed(const Event& event) {
DCHECK_EQ(kContextDisposed, 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(state_.next_gc_start_ms - event.time_ms);
}
}
void MemoryReducer::NotifyBackgroundIdleNotification(const Event& event) {
DCHECK_EQ(kBackgroundIdleNotification, event.type);
Action old_action = state_.action;
int old_started_gcs = state_.started_gcs;
state_ = Step(state_, event);
if (old_action == kWait && state_.action == kWait &&
old_started_gcs + 1 == state_.started_gcs) {
DCHECK(heap()->incremental_marking()->IsStopped());
// TODO(ulan): Replace it with incremental marking GC once
// chromium:490559 is fixed.
if (event.time_ms > state_.last_gc_time_ms + kLongDelayMs) {
heap()->CollectAllGarbage(Heap::kReduceMemoryFootprintMask,
"memory reducer background GC");
} else {
DCHECK(FLAG_incremental_marking);
heap()->StartIdleIncrementalMarking();
if (FLAG_trace_gc_verbose) {
PrintIsolate(heap()->isolate(),
"Memory reducer: started GC #%d"
" (background idle)\n",
state_.started_gcs);
}
}
}
}
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) {
return State(kDone, 0, 0, state.last_gc_time_ms);
}
switch (state.action) {
case kDone:
if (event.type == kTimer || event.type == kBackgroundIdleNotification) {
return state;
} else {
DCHECK(event.type == kContextDisposed || event.type == kMarkCompact);
return State(
kWait, 0, event.time_ms + kLongDelayMs,
event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms);
}
case kWait:
switch (event.type) {
case kContextDisposed:
return state;
case kTimer:
if (state.started_gcs >= kMaxNumberOfGCs) {
return State(kDone, kMaxNumberOfGCs, 0.0, state.last_gc_time_ms);
} else if (event.can_start_incremental_gc &&
(event.low_allocation_rate || 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);
} else {
return state;
}
} else {
return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
state.last_gc_time_ms);
}
case kBackgroundIdleNotification:
if (event.can_start_incremental_gc &&
state.started_gcs < kMaxNumberOfGCs) {
return State(kWait, state.started_gcs + 1,
event.time_ms + kLongDelayMs, state.last_gc_time_ms);
} else {
return state;
}
case kMarkCompact:
return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs,
event.time_ms);
}
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);
} else {
return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms);
}
}
}
UNREACHABLE();
return State(kDone, 0, 0, 0.0); // Make the compiler happy.
}
void MemoryReducer::ScheduleTimer(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); }
} // internal
} // v8
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