gc-idle-time-handler.h

Go to the documentation of this file.

// 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.
 
#ifndef V8_HEAP_GC_IDLE_TIME_HANDLER_H_
#define V8_HEAP_GC_IDLE_TIME_HANDLER_H_
 
#include "src/globals.h"
 
namespace v8 {
namespace internal {
 
enum GCIdleTimeActionType {
  DONE,
  DO_NOTHING,
  DO_INCREMENTAL_MARKING,
  DO_SCAVENGE,
  DO_FULL_GC,
  DO_FINALIZE_SWEEPING
};
 
 
class GCIdleTimeAction {
 public:
  static GCIdleTimeAction Done() {
    GCIdleTimeAction result;
    result.type = DONE;
    result.parameter = 0;
    return result;
  }
 
  static GCIdleTimeAction Nothing() {
    GCIdleTimeAction result;
    result.type = DO_NOTHING;
    result.parameter = 0;
    return result;
  }
 
  static GCIdleTimeAction IncrementalMarking(intptr_t step_size) {
    GCIdleTimeAction result;
    result.type = DO_INCREMENTAL_MARKING;
    result.parameter = step_size;
    return result;
  }
 
  static GCIdleTimeAction Scavenge() {
    GCIdleTimeAction result;
    result.type = DO_SCAVENGE;
    result.parameter = 0;
    return result;
  }
 
  static GCIdleTimeAction FullGC() {
    GCIdleTimeAction result;
    result.type = DO_FULL_GC;
    result.parameter = 0;
    return result;
  }
 
  static GCIdleTimeAction FinalizeSweeping() {
    GCIdleTimeAction result;
    result.type = DO_FINALIZE_SWEEPING;
    result.parameter = 0;
    return result;
  }
 
  void Print();
 
  GCIdleTimeActionType type;
  intptr_t parameter;
};
 
 
class GCTracer;
 
// The idle time handler makes decisions about which garbage collection
// operations are executing during IdleNotification.
class GCIdleTimeHandler {
 public:
  // 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;
 
  // Maximum mark-compact time returned by EstimateMarkCompactTime.
  static const size_t kMaxMarkCompactTimeInMs;
 
  // Minimum time to finalize sweeping phase. The main thread may wait for
  // sweeper threads.
  static const size_t kMinTimeForFinalizeSweeping;
 
  // Number of idle mark-compact events, after which idle handler will finish
  // idle round.
  static const int kMaxMarkCompactsInIdleRound;
 
  // Number of scavenges that will trigger start of new idle round.
  static const int kIdleScavengeThreshold;
 
  // Heap size threshold below which we prefer mark-compact over incremental
  // step.
  static const size_t kSmallHeapSize = 4 * kPointerSize * MB;
 
  // That is the maximum idle time we will have during frame rendering.
  static const size_t kMaxFrameRenderingIdleTime = 16;
 
  // If less than that much memory is left in the new space, we consider it
  // as almost full and force a new space collection earlier in the idle time.
  static const size_t kNewSpaceAlmostFullTreshold = 100 * KB;
 
  // If we haven't recorded any scavenger events yet, we use a conservative
  // lower bound for the scavenger speed.
  static const size_t kInitialConservativeScavengeSpeed = 100 * KB;
 
  struct HeapState {
    int contexts_disposed;
    size_t size_of_objects;
    bool incremental_marking_stopped;
    bool can_start_incremental_marking;
    bool sweeping_in_progress;
    size_t mark_compact_speed_in_bytes_per_ms;
    size_t incremental_marking_speed_in_bytes_per_ms;
    size_t scavenge_speed_in_bytes_per_ms;
    size_t available_new_space_memory;
    size_t new_space_capacity;
    size_t new_space_allocation_throughput_in_bytes_per_ms;
  };
 
  GCIdleTimeHandler()
      : mark_compacts_since_idle_round_started_(0),
        scavenges_since_last_idle_round_(0) {}
 
  GCIdleTimeAction Compute(size_t idle_time_in_ms, HeapState heap_state);
 
  void NotifyIdleMarkCompact() {
    if (mark_compacts_since_idle_round_started_ < kMaxMarkCompactsInIdleRound) {
      ++mark_compacts_since_idle_round_started_;
      if (mark_compacts_since_idle_round_started_ ==
          kMaxMarkCompactsInIdleRound) {
        scavenges_since_last_idle_round_ = 0;
      }
    }
  }
 
  void NotifyScavenge() { ++scavenges_since_last_idle_round_; }
 
  static size_t EstimateMarkingStepSize(size_t idle_time_in_ms,
                                        size_t marking_speed_in_bytes_per_ms);
 
  static size_t EstimateMarkCompactTime(
      size_t size_of_objects, size_t mark_compact_speed_in_bytes_per_ms);
 
  static size_t EstimateScavengeTime(size_t new_space_size,
                                     size_t scavenger_speed_in_bytes_per_ms);
 
  static bool ScavangeMayHappenSoon(
      size_t available_new_space_memory,
      size_t new_space_allocation_throughput_in_bytes_per_ms);
 
 private:
  void StartIdleRound() { mark_compacts_since_idle_round_started_ = 0; }
  bool IsMarkCompactIdleRoundFinished() {
    return mark_compacts_since_idle_round_started_ ==
           kMaxMarkCompactsInIdleRound;
  }
  bool EnoughGarbageSinceLastIdleRound() {
    return scavenges_since_last_idle_round_ >= kIdleScavengeThreshold;
  }
 
  int mark_compacts_since_idle_round_started_;
  int scavenges_since_last_idle_round_;
 
  DISALLOW_COPY_AND_ASSIGN(GCIdleTimeHandler);
};
 
}  // namespace internal
}  // namespace v8
 
#endif  // V8_HEAP_GC_IDLE_TIME_HANDLER_H_