Use an idle notification of 0ms as hint that a GC after context disposal is triggerd

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 {
@@ skipping 105 matching lines @@
 bool GCIdleTimeHandler::ShouldDoMarkCompact(
     size_t idle_time_in_ms, size_t size_of_objects,
     size_t mark_compact_speed_in_bytes_per_ms) {
   return idle_time_in_ms >=
          EstimateMarkCompactTime(size_of_objects,
                                  mark_compact_speed_in_bytes_per_ms);
 }
 
 
 // The following logic is implemented by the controller:
-// (1) If the new space is almost full and we can affort a Scavenge or if the
+// (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.
-// (2) If there is currently no MarkCompact idle round going on, we start a
+// (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.
-// (3) If incremental marking is done, we perform a full garbage collection
+// (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.
-// (4) If sweeping is in progress and we received a large enough idle time
+// (5) If sweeping is in progress and we received a large enough idle time
 // request, we finalize sweeping here.
-// (5) If incremental marking is in progress, we perform a marking step. Note,
+// (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) {
+        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) {
       StartIdleRound();
     } else {
       return GCIdleTimeAction::Done();
     }
   }
 
-  if (idle_time_in_ms == 0) {
-    return GCIdleTimeAction::Nothing();
-  }
-
   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)) {
       // 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 =
@@ skipping 18 matching lines @@
   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);
 }
 }
 }