Perform context disposal garbage collections only if contexts disposals happen at a high rate.

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

 // 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.
 
 #include "src/heap/gc-idle-time-handler.h"
 #include "src/heap/gc-tracer.h"
 #include "src/utils.h"
 
 namespace v8 {
 namespace internal {
 
 const double GCIdleTimeHandler::kConservativeTimeRatio = 0.9;
 const size_t GCIdleTimeHandler::kMaxMarkCompactTimeInMs = 1000;
 const size_t GCIdleTimeHandler::kMinTimeForFinalizeSweeping = 100;
 const int GCIdleTimeHandler::kMaxMarkCompactsInIdleRound = 7;
 const int GCIdleTimeHandler::kIdleScavengeThreshold = 5;
+const double GCIdleTimeHandler::kHighContextDisposalRate = 100;
 
 
 void GCIdleTimeAction::Print() {
   switch (type) {
     case DONE:
       PrintF("done");
       break;
     case DO_NOTHING:
       PrintF("no action");
       break;
@@ skipping 95 matching lines @@
 }
 
 
 // The following logic is implemented by the controller:
 // (1) If we don't have any idle time, do nothing, unless a context was
 // disposed, incremental marking is stopped, and the heap is small. Then do
 // a full GC.
 // (2) If the new space is almost full and we can affort a Scavenge or if the
 // next Scavenge will very likely take long, then a Scavenge is performed.
 // (3) If there is currently no MarkCompact idle round going on, we start a
-// new idle round if enough garbage was created or we received a context
-// disposal event. Otherwise we do not perform garbage collection to keep
-// system utilization low.
+// new idle round if enough garbage was created. Otherwise we do not perform
+// garbage collection to keep system utilization low.
 // (4) If incremental marking is done, we perform a full garbage collection
-// if context was disposed or if we are allowed to still do full garbage
-// collections during this idle round or if we are not allowed to start
-// incremental marking. Otherwise we do not perform garbage collection to
-// keep system utilization low.
+// if  we are allowed to still do full garbage collections during this idle
+// round or if we are not allowed to start incremental marking. Otherwise we
+// do not perform garbage collection to keep system utilization low.
 // (5) If sweeping is in progress and we received a large enough idle time
 // request, we finalize sweeping here.
 // (6) If incremental marking is in progress, we perform a marking step. Note,
 // that this currently may trigger a full garbage collection.
 GCIdleTimeAction GCIdleTimeHandler::Compute(size_t idle_time_in_ms,
                                             HeapState heap_state) {
   if (idle_time_in_ms == 0) {
     if (heap_state.incremental_marking_stopped) {
       if (heap_state.size_of_objects < kSmallHeapSize &&
-          heap_state.contexts_disposed > 0) {
+          heap_state.contexts_disposed > 0 &&
+          heap_state.contexts_disposal_rate < kHighContextDisposalRate) {
         return GCIdleTimeAction::FullGC();
       }
     }
     return GCIdleTimeAction::Nothing();
   }
 
   if (ShouldDoScavenge(
           idle_time_in_ms, heap_state.new_space_capacity,
           heap_state.used_new_space_size,
           heap_state.scavenge_speed_in_bytes_per_ms,
           heap_state.new_space_allocation_throughput_in_bytes_per_ms)) {
     return GCIdleTimeAction::Scavenge();
   }
 
   if (IsMarkCompactIdleRoundFinished()) {
-    if (EnoughGarbageSinceLastIdleRound() || heap_state.contexts_disposed > 0) {
+    if (EnoughGarbageSinceLastIdleRound()) {
       StartIdleRound();
     } else {
       return GCIdleTimeAction::Done();
     }
   }
 
   if (heap_state.incremental_marking_stopped) {
-    // TODO(jochen): Remove context disposal dependant logic.
     if (ShouldDoMarkCompact(idle_time_in_ms, heap_state.size_of_objects,
-                            heap_state.mark_compact_speed_in_bytes_per_ms) ||
-        (heap_state.size_of_objects < kSmallHeapSize &&
-         heap_state.contexts_disposed > 0)) {
+                            heap_state.mark_compact_speed_in_bytes_per_ms)) {
       // If there are no more than two GCs left in this idle round and we are
       // allowed to do a full GC, then make those GCs full in order to compact
       // the code space.
       // TODO(ulan): Once we enable code compaction for incremental marking, we
       // can get rid of this special case and always start incremental marking.
       int remaining_mark_sweeps =
           kMaxMarkCompactsInIdleRound - mark_compacts_since_idle_round_started_;
-      if (heap_state.contexts_disposed > 0 ||
-          (idle_time_in_ms > kMaxFrameRenderingIdleTime &&
-           (remaining_mark_sweeps <= 2 ||
-            !heap_state.can_start_incremental_marking))) {
+      if (idle_time_in_ms > kMaxFrameRenderingIdleTime &&
+          (remaining_mark_sweeps <= 2 ||
+           !heap_state.can_start_incremental_marking)) {
         return GCIdleTimeAction::FullGC();
       }
     }
     if (!heap_state.can_start_incremental_marking) {
       return GCIdleTimeAction::Nothing();
     }
   }
   // TODO(hpayer): Estimate finalize sweeping time.
   if (heap_state.sweeping_in_progress &&
       idle_time_in_ms >= kMinTimeForFinalizeSweeping) {
     return GCIdleTimeAction::FinalizeSweeping();
   }
 
   if (heap_state.incremental_marking_stopped &&
       !heap_state.can_start_incremental_marking) {
     return GCIdleTimeAction::Nothing();
   }
   size_t step_size = EstimateMarkingStepSize(
       idle_time_in_ms, heap_state.incremental_marking_speed_in_bytes_per_ms);
   return GCIdleTimeAction::IncrementalMarking(step_size);
 }
 }
 }