Limit rate of full garbage collections triggered by idle notification.

src/heap/gc-idle-time-handler.h

 // 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 {
@@ skipping 118 matching lines @@
   // 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;
 
   // 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;
 
+  // This is the minimum time required to perform over approximation of
+  // weak closure during idle notification.
   static const size_t kMinTimeForOverApproximatingWeakClosureInMs;
 
+  // No full garbage collections are performed if the last full GC was done
+  // kMinTimeInBetweenMarkCompactsInMs milliseconds before. Idle times larger
+  // than kMaxScheduledIdleTime ignore that threshold.
+  static const size_t kMinTimeInBetweenMarkCompactsInMs = 1000;

[rmcilroy, 2015/03/20 14:56:08]

Is 1000ms a guesstimation or is there any reason to think that pages shouldn't
really need full GCs within 1s?

+
   class HeapState {
    public:
     void Print();
 
     int contexts_disposed;
     double contexts_disposal_rate;
     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 final_incremental_mark_compact_speed_in_bytes_per_ms;
     size_t scavenge_speed_in_bytes_per_ms;
     size_t used_new_space_size;
     size_t new_space_capacity;
     size_t new_space_allocation_throughput_in_bytes_per_ms;
+    size_t last_mark_compact_time;
+    size_t current_time;
   };
 
   GCIdleTimeHandler()
       : mark_compacts_since_idle_round_started_(0),
         scavenges_since_last_idle_round_(0) {}
 
   GCIdleTimeAction Compute(double idle_time_in_ms, HeapState heap_state);
 
   void NotifyIdleMarkCompact() {
     if (mark_compacts_since_idle_round_started_ < kMaxMarkCompactsInIdleRound) {
@@ skipping 11 matching lines @@
                                         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 EstimateFinalIncrementalMarkCompactTime(
       size_t size_of_objects, size_t mark_compact_speed_in_bytes_per_ms);
 
   static bool ShouldDoMarkCompact(size_t idle_time_in_ms,
                                   size_t size_of_objects,
-                                  size_t mark_compact_speed_in_bytes_per_ms);
+                                  size_t mark_compact_speed_in_bytes_per_ms,
+                                  size_t last_mark_compact_time_in_ms,
+                                  size_t current_time_in_ms);
 
   static bool ShouldDoContextDisposalMarkCompact(int context_disposed,
                                                  double contexts_disposal_rate);
 
   static bool ShouldDoFinalIncrementalMarkCompact(
       size_t idle_time_in_ms, size_t size_of_objects,
       size_t final_incremental_mark_compact_speed_in_bytes_per_ms);
 
   static bool ShouldDoOverApproximateWeakClosure(size_t idle_time_in_ms);
 
@@ skipping 15 matching lines @@
   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_