Make full GC reduce memory footprint an explicit event in the idle notification handler.

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 {
 namespace internal {
 
 enum GCIdleTimeActionType {
   DONE,
   DO_NOTHING,
   DO_INCREMENTAL_MARKING,
   DO_SCAVENGE,
   DO_FULL_GC,
+  DO_FULL_GC_COMPACT,
   DO_FINALIZE_SWEEPING
 };
 
 
 class GCIdleTimeAction {
  public:
   static GCIdleTimeAction Done() {
     GCIdleTimeAction result;
     result.type = DONE;
     result.parameter = 0;
@@ skipping 26 matching lines @@
   }
 
   static GCIdleTimeAction FullGC() {
     GCIdleTimeAction result;
     result.type = DO_FULL_GC;
     result.parameter = 0;
     result.additional_work = false;
     return result;
   }
 
+  static GCIdleTimeAction FullGCCompact() {
+    GCIdleTimeAction result;
+    result.type = DO_FULL_GC_COMPACT;
+    result.parameter = 0;
+    result.additional_work = false;
+    return result;
+  }
+
   static GCIdleTimeAction FinalizeSweeping() {
     GCIdleTimeAction result;
     result.type = DO_FINALIZE_SWEEPING;
     result.parameter = 0;
     result.additional_work = false;
     return result;
   }
 
   void Print();
 
@@ skipping 40 matching lines @@
   // idle round.
   static const int kMaxMarkCompactsInIdleRound;
 
   // Number of scavenges that will trigger start of new idle round.
   static const int kIdleScavengeThreshold;
 
   // This is the maximum scheduled idle time. Note that it can be more than
   // 16 ms when there is currently no rendering going on.
   static const size_t kMaxScheduledIdleTime = 50;
 
+  // This is the minimum time needed to trigger a full garbage collection which
+  // tries to reduce memory footprint.
+  static const size_t kMinTimeForReduceMemory = 600;

[rmcilroy, 2015/04/10 11:14:35]

I'm guessing you are relying on the 1000ms IdleHandler code here? Once we move
this to be an idle task we should probably change this to allow
DO_FULL_GC_COMPACT for smaller deadlines, but have abortable compaction.

[Hannes Payer (out of office), 2015/04/10 13:06:57]

Yes, exactly.

+
   // We conservatively assume that in the next kTimeUntilNextIdleEvent ms
   // no idle notification happens.
   static const size_t kTimeUntilNextIdleEvent = 100;
 
   // 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;
@@ skipping 53 matching lines @@
   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);
 
+  static bool ShouldDoReduceMemoryMarkCompact(size_t idle_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);
 
   static bool ShouldDoScavenge(
@@ skipping 20 matching lines @@
   int scavenges_since_last_idle_round_;
   int idle_times_which_made_no_progress_since_last_idle_round_;
 
   DISALLOW_COPY_AND_ASSIGN(GCIdleTimeHandler);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_GC_IDLE_TIME_HANDLER_H_