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// Copyright 2014 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/globals.h"
namespace v8 {
namespace internal {
enum GCIdleTimeActionType {
class GCIdleTimeAction {
static GCIdleTimeAction Done() {
GCIdleTimeAction result;
result.type = DONE;
result.additional_work = false;
return result;
static GCIdleTimeAction Nothing() {
GCIdleTimeAction result;
result.type = DO_NOTHING;
result.additional_work = false;
return result;
static GCIdleTimeAction IncrementalStep() {
GCIdleTimeAction result;
result.type = DO_INCREMENTAL_STEP;
result.additional_work = false;
return result;
static GCIdleTimeAction FullGC() {
GCIdleTimeAction result;
result.type = DO_FULL_GC;
result.additional_work = false;
return result;
void Print();
GCIdleTimeActionType type;
bool additional_work;
class GCIdleTimeHeapState {
void Print();
int contexts_disposed;
double contexts_disposal_rate;
size_t size_of_objects;
bool incremental_marking_stopped;
// The idle time handler makes decisions about which garbage collection
// operations are executing during IdleNotification.
class V8_EXPORT_PRIVATE GCIdleTimeHandler {
// If we haven't recorded any incremental marking events yet, we carefully
// mark with a conservative lower bound for the marking speed.
static const size_t kInitialConservativeMarkingSpeed = 100 * KB;
// Maximum marking step size returned by EstimateMarkingStepSize.
static const size_t kMaximumMarkingStepSize = 700 * MB;
// We have to make sure that we finish the IdleNotification before
// idle_time_in_ms. Hence, we conservatively prune our workload estimate.
static const double kConservativeTimeRatio;
// If we haven't recorded any mark-compact events yet, we use
// conservative lower bound for the mark-compact speed.
static const size_t kInitialConservativeMarkCompactSpeed = 2 * MB;
// If we haven't recorded any final incremental mark-compact events yet, we
// use conservative lower bound for the mark-compact speed.
static const size_t kInitialConservativeFinalIncrementalMarkCompactSpeed =
2 * MB;
// Maximum final incremental mark-compact time returned by
// EstimateFinalIncrementalMarkCompactTime.
static const size_t kMaxFinalIncrementalMarkCompactTimeInMs;
// This is the maximum scheduled idle time. Note that it can be more than
// 16.66 ms when there is currently no rendering going on.
static const size_t kMaxScheduledIdleTime = 50;
// The maximum idle time when frames are rendered is 16.66ms.
static const size_t kMaxFrameRenderingIdleTime = 17;
static const int kMinBackgroundIdleTime = 900;
// An allocation throughput below kLowAllocationThroughput bytes/ms is
// considered low
static const size_t kLowAllocationThroughput = 1000;
static const size_t kMaxHeapSizeForContextDisposalMarkCompact = 100 * MB;
// If contexts are disposed at a higher rate a full gc is triggered.
static const double kHighContextDisposalRate;
// Incremental marking step time.
static const size_t kIncrementalMarkingStepTimeInMs = 1;
static const size_t kMinTimeForOverApproximatingWeakClosureInMs;
// Number of times we will return a Nothing action in the current mode
// despite having idle time available before we returning a Done action to
// ensure we don't keep scheduling idle tasks and making no progress.
static const int kMaxNoProgressIdleTimes = 10;
GCIdleTimeHandler() : idle_times_which_made_no_progress_(0) {}
GCIdleTimeAction Compute(double idle_time_in_ms,
GCIdleTimeHeapState heap_state);
bool Enabled();
void ResetNoProgressCounter() { idle_times_which_made_no_progress_ = 0; }
static size_t EstimateMarkingStepSize(double idle_time_in_ms,
double marking_speed_in_bytes_per_ms);
static double EstimateFinalIncrementalMarkCompactTime(
size_t size_of_objects, double mark_compact_speed_in_bytes_per_ms);
static bool ShouldDoContextDisposalMarkCompact(int context_disposed,
double contexts_disposal_rate,
size_t size_of_objects);
static bool ShouldDoFinalIncrementalMarkCompact(
double idle_time_in_ms, size_t size_of_objects,
double final_incremental_mark_compact_speed_in_bytes_per_ms);
static bool ShouldDoOverApproximateWeakClosure(double idle_time_in_ms);
GCIdleTimeAction NothingOrDone(double idle_time_in_ms);
// Idle notifications with no progress.
int idle_times_which_made_no_progress_;
} // namespace internal
} // namespace v8