Check if there is still time before finalizing an incremental collection.

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 45 matching lines @@
 
   if (marking_step_size > kMaximumMarkingStepSize)
     return kMaximumMarkingStepSize;
 
   return static_cast<size_t>(marking_step_size * kConservativeTimeRatio);
 }
 
 
 size_t GCIdleTimeHandler::EstimateMarkCompactTime(
     size_t size_of_objects, size_t mark_compact_speed_in_bytes_per_ms) {
+  // TODO(hpayer): Be more precise about the type of mark-compact event. It
+  // makes a huge difference if it is incremental or non-incremental and if
+  // compaction is happening.
   if (mark_compact_speed_in_bytes_per_ms == 0) {
     mark_compact_speed_in_bytes_per_ms = kInitialConservativeMarkCompactSpeed;
   }
   size_t result = size_of_objects / mark_compact_speed_in_bytes_per_ms;
   return Min(result, kMaxMarkCompactTimeInMs);
 }
 
 
-bool GCIdleTimeHandler::DoScavenge(
+bool GCIdleTimeHandler::ShouldDoScavenge(
     size_t idle_time_in_ms, size_t new_space_size, size_t used_new_space_size,
     size_t scavenge_speed_in_bytes_per_ms,
     size_t new_space_allocation_throughput_in_bytes_per_ms) {
   size_t new_space_allocation_limit =
       kMaxFrameRenderingIdleTime * scavenge_speed_in_bytes_per_ms;
 
   // If the limit is larger than the new space size, then scavenging used to be
   // really fast. We can take advantage of the whole new space.
   if (new_space_allocation_limit > new_space_size) {
     new_space_allocation_limit = new_space_size;
@@ skipping 18 matching lines @@
   if (new_space_allocation_limit <= used_new_space_size) {
     if (used_new_space_size / scavenge_speed_in_bytes_per_ms <=
         idle_time_in_ms) {
       return true;
     }
   }
   return false;
 }
 
 
+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
 // 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
 // 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
 // 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
 // request, we finalize sweeping here.
 // (5) 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 (DoScavenge(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)) {
+  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) {
-    size_t estimated_time_in_ms =
-        EstimateMarkCompactTime(heap_state.size_of_objects,
-                                heap_state.mark_compact_speed_in_bytes_per_ms);
-    if (idle_time_in_ms >= estimated_time_in_ms ||
+    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 =
           kMaxMarkCompactsInIdleRound - mark_compacts_since_idle_round_started_;
       if (heap_state.contexts_disposed > 0 ||
@@ skipping 16 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);
 }
 }
 }