Adjust heuristics for idle notifications after context disposal.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4803 matching lines @@
 
 void Heap::EnsureHeapIsIterable() {
   ASSERT(IsAllocationAllowed());
   if (!IsHeapIterable()) {
     CollectAllGarbage(kMakeHeapIterableMask, "Heap::EnsureHeapIsIterable");
   }
   ASSERT(IsHeapIterable());
 }
 
 
+void Heap::AdvanceIdleIncrementalMarking(intptr_t step_size) {

[ulan, 2012/03/16 13:37:23]

This function is extracted from lines 4876-4894 of IdleNotification().

+  // This flag prevents incremental marking from requesting GC via stack guard
+  idle_notification_will_schedule_next_gc_ = true;
+  incremental_marking()->Step(step_size);
+  idle_notification_will_schedule_next_gc_ = false;
+
+  if (incremental_marking()->IsComplete()) {
+    bool uncommit = false;
+    if (gc_count_at_last_idle_gc_ == gc_count_) {
+      // No GC since the last full GC, the mutator is probably not active.
+      isolate_->compilation_cache()->Clear();
+      uncommit = true;
+    }
+    CollectAllGarbage(kNoGCFlags, "idle notification: finalize incremental");
+    gc_count_at_last_idle_gc_ = gc_count_;
+    if (uncommit) {
+      new_space_.Shrink();
+      UncommitFromSpace();
+    }
+  }
+}
+
+
 bool Heap::IdleNotification(int hint) {
-  if (hint >= 1000) return IdleGlobalGC();
-  if (contexts_disposed_ > 0 || !FLAG_incremental_marking ||
+  intptr_t size_factor = Min(Max(hint, 30), 1000) / 10;
+  // The size factor is in range [3..100].
+  intptr_t step_size = size_factor * IncrementalMarking::kAllocatedThreshold;
+
+  if (contexts_disposed_ > 0) {
+    if (hint > TimeMarkSweepWouldTakeInMs() && !FLAG_expose_gc) {
+      HistogramTimerScope scope(isolate_->counters()->gc_context());
+      CollectAllGarbage(kReduceMemoryFootprintMask,
+                        "idle notification: contexts disposed");
+    } else {
+      AdvanceIdleIncrementalMarking(step_size);
+      contexts_disposed_ = 0;
+    }
+    // Make sure that we have no pending context disposals.
+    // Take into account that we might have decided to delay full collection
+    // because incremental marking is in progress.
+    ASSERT((contexts_disposed_ == 0) || !incremental_marking()->IsStopped());
+    return false;
+  }
+
+  if (hint >= 1000 || !FLAG_incremental_marking ||

[ulan, 2012/03/16 13:37:23]

Once this CL lands into Chromium without memory regressions, I will refactor
this to remove the (hint >= 1000) condition and get rid of IdleGlobalGC.

       FLAG_expose_gc || Serializer::enabled()) {
-    return true;
+    return IdleGlobalGC();
   }
 
   // By doing small chunks of GC work in each IdleNotification,
   // perform a round of incremental GCs and after that wait until
   // the mutator creates enough garbage to justify a new round.
   // An incremental GC progresses as follows:
   // 1. many incremental marking steps,
   // 2. one old space mark-sweep-compact,
   // 3. many lazy sweep steps.
   // Use mark-sweep-compact events to count incremental GCs in a round.
 
-  intptr_t size_factor = Min(Max(hint, 30), 1000) / 10;
-  // The size factor is in range [3..100].
-  intptr_t step_size = size_factor * IncrementalMarking::kAllocatedThreshold;
 
   if (incremental_marking()->IsStopped()) {
     if (!IsSweepingComplete() &&
         !AdvanceSweepers(static_cast<int>(step_size))) {
       return false;
     }
   }
 
   if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
     if (EnoughGarbageSinceLastIdleRound()) {
       StartIdleRound();
     } else {
       return true;
     }
   }
 
   int new_mark_sweeps = ms_count_ - ms_count_at_last_idle_notification_;
   mark_sweeps_since_idle_round_started_ += new_mark_sweeps;
   ms_count_at_last_idle_notification_ = ms_count_;
 
   if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
     FinishIdleRound();
     return true;
   }
 
   if (incremental_marking()->IsStopped()) {
-    if (hint < 1000 && !WorthStartingGCWhenIdle()) {
+    if (!WorthStartingGCWhenIdle()) {
       FinishIdleRound();
       return true;
     }
     incremental_marking()->Start();
   }
 
-  // This flag prevents incremental marking from requesting GC via stack guard
-  idle_notification_will_schedule_next_gc_ = true;
-  incremental_marking()->Step(step_size);
-  idle_notification_will_schedule_next_gc_ = false;
-
-  if (incremental_marking()->IsComplete()) {
-    bool uncommit = false;
-    if (gc_count_at_last_idle_gc_ == gc_count_) {
-      // No GC since the last full GC, the mutator is probably not active.
-      isolate_->compilation_cache()->Clear();
-      uncommit = true;
-    }
-    CollectAllGarbage(kNoGCFlags, "idle notification: finalize incremental");
-    gc_count_at_last_idle_gc_ = gc_count_;
-    if (uncommit) {
-      new_space_.Shrink();
-      UncommitFromSpace();
-    }
-  }
+  AdvanceIdleIncrementalMarking(step_size);
   return false;
 }
 
 
 bool Heap::IdleGlobalGC() {
   static const int kIdlesBeforeScavenge = 4;
   static const int kIdlesBeforeMarkSweep = 7;
   static const int kIdlesBeforeMarkCompact = 8;
   static const int kMaxIdleCount = kIdlesBeforeMarkCompact + 1;
   static const unsigned int kGCsBetweenCleanup = 4;
@@ skipping 12 matching lines @@
   // provoke a number of garbage collections.
   if (gc_count_ - last_idle_notification_gc_count_ < kGCsBetweenCleanup) {
     number_idle_notifications_ =
         Min(number_idle_notifications_ + 1, kMaxIdleCount);
   } else {
     number_idle_notifications_ = 0;
     last_idle_notification_gc_count_ = gc_count_;
   }
 
   if (number_idle_notifications_ == kIdlesBeforeScavenge) {
-    if (contexts_disposed_ > 0) {
-      HistogramTimerScope scope(isolate_->counters()->gc_context());
-      CollectAllGarbage(kReduceMemoryFootprintMask,
-                        "idle notification: contexts disposed");
-    } else {
-      CollectGarbage(NEW_SPACE, "idle notification");
-    }
+    CollectGarbage(NEW_SPACE, "idle notification");
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
   } else if (number_idle_notifications_ == kIdlesBeforeMarkSweep) {
     // Before doing the mark-sweep collections we clear the
     // compilation cache to avoid hanging on to source code and
     // generated code for cached functions.
     isolate_->compilation_cache()->Clear();
 
     CollectAllGarbage(kReduceMemoryFootprintMask, "idle notification");
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
 
   } else if (number_idle_notifications_ == kIdlesBeforeMarkCompact) {
     CollectAllGarbage(kReduceMemoryFootprintMask, "idle notification");
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
     number_idle_notifications_ = 0;
     finished = true;
-  } else if (contexts_disposed_ > 0) {
-    if (FLAG_expose_gc) {
-      contexts_disposed_ = 0;
-    } else {
-      HistogramTimerScope scope(isolate_->counters()->gc_context());
-      CollectAllGarbage(kReduceMemoryFootprintMask,
-                        "idle notification: contexts disposed");
-      last_idle_notification_gc_count_ = gc_count_;
-    }
-    // If this is the first idle notification, we reset the
-    // notification count to avoid letting idle notifications for
-    // context disposal garbage collections start a potentially too
-    // aggressive idle GC cycle.
-    if (number_idle_notifications_ <= 1) {
-      number_idle_notifications_ = 0;
-      uncommit = false;
-    }
   } else if (number_idle_notifications_ > kIdlesBeforeMarkCompact) {
     // If we have received more than kIdlesBeforeMarkCompact idle
     // notifications we do not perform any cleanup because we don't
     // expect to gain much by doing so.
     finished = true;
   }
 
-  // Make sure that we have no pending context disposals and
-  // conditionally uncommit from space.
-  // Take into account that we might have decided to delay full collection
-  // because incremental marking is in progress.
-  ASSERT((contexts_disposed_ == 0) || !incremental_marking()->IsStopped());
   if (uncommit) UncommitFromSpace();
 
   return finished;
 }
 
 
 #ifdef DEBUG
 
 void Heap::Print() {
   if (!HasBeenSetUp()) return;
@@ skipping 1974 matching lines @@
   isolate_->heap()->store_buffer()->Compact();
   isolate_->heap()->store_buffer()->Filter(MemoryChunk::ABOUT_TO_BE_FREED);
   for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
     next = chunk->next_chunk();
     isolate_->memory_allocator()->Free(chunk);
   }
   chunks_queued_for_free_ = NULL;
 }
 
 } }  // namespace v8::internal