Perform scavenge in idle tasks.

src/heap/scavenge-job.h

+// 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.
+
+#ifndef V8_HEAP_SCAVENGE_JOB_H_
+#define V8_HEAP_SCAVENGE_JOB_H_
+
+#include "src/cancelable-task.h"
+#include "src/heap/gc-tracer.h"
+
+namespace v8 {
+namespace internal {
+
+class Heap;
+class Isolate;
+
+
+// This class posts idle tasks and performs scavenges in the idle tasks.
+class ScavengeJob {
+ public:
+  class IdleTask : public CancelableIdleTask {
+   public:
+    explicit IdleTask(Isolate* isolate, ScavengeJob* job)
+        : CancelableIdleTask(isolate), job_(job) {}
+    // CancelableIdleTask overrides.
+    void RunInternal(double deadline_in_seconds) override;
+
+   private:
+    ScavengeJob* job_;
+  };
+
+  ScavengeJob()
+      : idle_task_pending_(false),
+        idle_task_rescheduled_(false),
+        bytes_allocated_since_the_last_task_(0) {}
+
+  // Posts an idle task if the cumulative bytes allocated since the last
+  // idle task exceed kBytesAllocatedBeforeNextIdleTask.
+  void ScheduleIdleTaskIfNeeded(Heap* heap, int bytes_allocated);
+
+  // Posts an idle task ignoring the bytes allocated, but makes sure
+  // that the new idle task cannot reschedule again.
+  // This prevents infinite rescheduling.
+  void RescheduleIdleTask(Heap* heap);
+
+  bool IdleTaskPending() { return idle_task_pending_; }
+  void NotifyIdleTask() { idle_task_pending_ = false; }
+  bool IdleTaskRescheduled() { return idle_task_rescheduled_; }
+
+  static bool ReachedIdleAllocationLimit(size_t scavenge_speed_in_bytes_per_ms,
+                                         size_t new_space_size,
+                                         size_t new_space_capacity);
+
+  static bool EnoughIdleTimeForScavenge(double idle_time_ms,
+                                        size_t scavenge_speed_in_bytes_per_ms,
+                                        size_t new_space_size);
+
+  // If we haven't recorded any scavenger events yet, we use a conservative
+  // lower bound for the scavenger speed.
+  static const int kInitialScavengeSpeedInBytesPerMs = 256 * KB;
+  // Estimate of the average idle time that an idle task gets.
+  static const int kAverageIdleTimeMs = 5;
+  // The number of bytes to be allocated in new space before the next idle
+  // task is posted.
+  static const size_t kBytesAllocatedBeforeNextIdleTask = 512 * KB;
+  // The minimum size of allocated new space objects to trigger a scavenge.
+  static const size_t kMinAllocationLimit = 512 * KB;
+  // The allocation limit cannot exceed this fraction of the new space capacity.
+  static const double kMaxAllocationLimitAsFractionOfNewSpace;
+
+ private:
+  void ScheduleIdleTask(Heap* heap);
+  bool idle_task_pending_;
+  bool idle_task_rescheduled_;
+  int bytes_allocated_since_the_last_task_;
+};
+}
+}  // namespace v8::internal
+
+#endif  // V8_HEAP_SCAVENGE_JOB_H_