Reland "Replace reduce-memory mode in idle notification with delayed clean-up GC."

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

Index: src/heap/gc-idle-time-handler.cc
diff --git a/src/heap/gc-idle-time-handler.cc b/src/heap/gc-idle-time-handler.cc
index ab84a7301bb2d81ca9c50f6f141e125d28e58330..efce981ee8c2037a60216e222384de34cf7408e8 100644
--- a/src/heap/gc-idle-time-handler.cc
+++ b/src/heap/gc-idle-time-handler.cc
@@ -50,7 +50,6 @@ void GCIdleTimeHandler::HeapState::Print() {
   PrintF("contexts_disposal_rate=%f ", contexts_disposal_rate);
   PrintF("size_of_objects=%" V8_PTR_PREFIX "d ", size_of_objects);
   PrintF("incremental_marking_stopped=%d ", incremental_marking_stopped);
-  PrintF("can_start_incremental_marking=%d ", can_start_incremental_marking);
   PrintF("sweeping_in_progress=%d ", sweeping_in_progress);
   PrintF("has_low_allocation_rate=%d", has_low_allocation_rate);
   PrintF("mark_compact_speed=%" V8_PTR_PREFIX "d ",
@@ -195,70 +194,15 @@ bool GCIdleTimeHandler::ShouldDoOverApproximateWeakClosure(
 
 
 GCIdleTimeAction GCIdleTimeHandler::NothingOrDone() {
-  if (idle_times_which_made_no_progress_per_mode_ >=
-      kMaxNoProgressIdleTimesPerMode) {
+  if (idle_times_which_made_no_progress_ >= kMaxNoProgressIdleTimes) {
     return GCIdleTimeAction::Done();
   } else {
-    idle_times_which_made_no_progress_per_mode_++;
+    idle_times_which_made_no_progress_++;
     return GCIdleTimeAction::Nothing();
   }
 }
 
 
-// The idle time handler has three modes and transitions between them
-// as shown in the diagram:
-//
-//  kReduceLatency -----> kReduceMemory -----> kDone
-//      ^    ^                  |                |
-//      |    |                  |                |
-//      |    +------------------+                |
-//      |                                        |
-//      +----------------------------------------+
-//
-// In kReduceLatency mode the handler only starts incremental marking
-// if can_start_incremental_marking is false.
-// In kReduceMemory mode the handler can force a new GC cycle by starting
-// incremental marking even if can_start_incremental_marking is false. It can
-// cause at most X idle GCs.
-// In kDone mode the idle time handler does nothing.
-//
-// The initial mode is kReduceLatency.
-//
-// kReduceLatency => kReduceMemory transition happens if there were Y
-// consecutive long idle notifications without any mutator GC. This is our
-// notion of "mutator is idle".
-//
-// kReduceMemory => kDone transition happens after X idle GCs.
-//
-// kReduceMemory => kReduceLatency transition happens if N mutator GCs
-// were performed meaning that the mutator is active.
-//
-// kDone => kReduceLatency transition happens if there were M mutator GCs or
-// context was disposed.
-//
-// X = kMaxIdleMarkCompacts
-// Y = kLongIdleNotificationsBeforeMutatorIsIdle
-// N = #(idle GCs)
-// M = kGCsBeforeMutatorIsActive
-GCIdleTimeAction GCIdleTimeHandler::Compute(double idle_time_in_ms,
-                                            HeapState heap_state) {
-  Mode next_mode = NextMode(heap_state);
-
-  if (next_mode != mode_) {
-    mode_ = next_mode;
-    ResetCounters();
-  }
-
-  UpdateCounters(idle_time_in_ms);
-
-  if (mode_ == kDone) {
-    return GCIdleTimeAction::Done();
-  } else {
-    return Action(idle_time_in_ms, heap_state, mode_ == kReduceMemory);
-  }
-}
-
-
 // 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
@@ -267,26 +211,18 @@ GCIdleTimeAction GCIdleTimeHandler::Compute(double idle_time_in_ms,
 // we do nothing until the context disposal rate becomes lower.
 // (3) 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.
-// (4) If there is currently no MarkCompact idle round going on, we start a
-// new idle round if enough garbage was created. Otherwise we do not perform
-// garbage collection to keep system utilization low.
-// (5) If incremental marking is done, we perform a full garbage collection
-// 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.
-// (6) If sweeping is in progress and we received a large enough idle time
+// (4) If sweeping is in progress and we received a large enough idle time
 // request, we finalize sweeping here.
-// (7) If incremental marking is in progress, we perform a marking step. Note,
+// (5) If incremental marking is in progress, we perform a marking step. Note,
 // that this currently may trigger a full garbage collection.
-GCIdleTimeAction GCIdleTimeHandler::Action(double idle_time_in_ms,
-                                           const HeapState& heap_state,
-                                           bool reduce_memory) {
+GCIdleTimeAction GCIdleTimeHandler::Compute(double idle_time_in_ms,
+                                            HeapState heap_state) {
   if (static_cast<int>(idle_time_in_ms) <= 0) {
     if (heap_state.incremental_marking_stopped) {
       if (ShouldDoContextDisposalMarkCompact(
               heap_state.contexts_disposed,
               heap_state.contexts_disposal_rate)) {
-        return GCIdleTimeAction::FullGC(false);
+        return GCIdleTimeAction::FullGC();
       }
     }
     return GCIdleTimeAction::Nothing();
@@ -307,14 +243,6 @@ GCIdleTimeAction GCIdleTimeHandler::Action(double idle_time_in_ms,
     return GCIdleTimeAction::Scavenge();
   }
 
-  if (heap_state.incremental_marking_stopped && reduce_memory) {
-    if (ShouldDoMarkCompact(static_cast<size_t>(idle_time_in_ms),
-                            heap_state.size_of_objects,
-                            heap_state.mark_compact_speed_in_bytes_per_ms)) {
-      return GCIdleTimeAction::FullGC(reduce_memory);
-    }
-  }
-
   if (heap_state.sweeping_in_progress) {
     if (heap_state.sweeping_completed) {
       return GCIdleTimeAction::FinalizeSweeping();
@@ -323,95 +251,16 @@ GCIdleTimeAction GCIdleTimeHandler::Action(double idle_time_in_ms,
     }
   }
 
-  if (!FLAG_incremental_marking ||
-      (heap_state.incremental_marking_stopped &&
-       !heap_state.can_start_incremental_marking && !reduce_memory)) {
-    return NothingOrDone();
+  if (!FLAG_incremental_marking || heap_state.incremental_marking_stopped) {
+    return GCIdleTimeAction::Done();
   }
 
   size_t step_size = EstimateMarkingStepSize(
       static_cast<size_t>(kIncrementalMarkingStepTimeInMs),
       heap_state.incremental_marking_speed_in_bytes_per_ms);
-  return GCIdleTimeAction::IncrementalMarking(step_size, reduce_memory);
+  return GCIdleTimeAction::IncrementalMarking(step_size);
 }
 
 
-void GCIdleTimeHandler::UpdateCounters(double idle_time_in_ms) {
-  if (mode_ == kReduceLatency) {
-    int gcs = scavenges_ + mark_compacts_;
-    if (gcs > 0) {
-      // There was a GC since the last notification.
-      long_idle_notifications_ = 0;
-      background_idle_notifications_ = 0;
-    }
-    idle_mark_compacts_ = 0;
-    mark_compacts_ = 0;
-    scavenges_ = 0;
-    if (idle_time_in_ms >= kMinBackgroundIdleTime) {
-      background_idle_notifications_++;
-    } else if (idle_time_in_ms >= kMinLongIdleTime) {
-      long_idle_notifications_++;
-    }
-  }
-}
-
-
-void GCIdleTimeHandler::ResetCounters() {
-  long_idle_notifications_ = 0;
-  background_idle_notifications_ = 0;
-  idle_mark_compacts_ = 0;
-  mark_compacts_ = 0;
-  scavenges_ = 0;
-  idle_times_which_made_no_progress_per_mode_ = 0;
-}
-
-
-bool GCIdleTimeHandler::IsMutatorActive(int contexts_disposed,
-                                        int mark_compacts) {
-  return contexts_disposed > 0 ||
-         mark_compacts >= kMarkCompactsBeforeMutatorIsActive;
-}
-
-
-bool GCIdleTimeHandler::IsMutatorIdle(int long_idle_notifications,
-                                      int background_idle_notifications,
-                                      int mutator_gcs) {
-  return mutator_gcs == 0 &&
-         (long_idle_notifications >=
-              kLongIdleNotificationsBeforeMutatorIsIdle ||
-          background_idle_notifications >=
-              kBackgroundIdleNotificationsBeforeMutatorIsIdle);
-}
-
-
-GCIdleTimeHandler::Mode GCIdleTimeHandler::NextMode(
-    const HeapState& heap_state) {
-  DCHECK(mark_compacts_ >= idle_mark_compacts_);
-  int mutator_gcs = scavenges_ + mark_compacts_ - idle_mark_compacts_;
-  switch (mode_) {
-    case kDone:
-      DCHECK(idle_mark_compacts_ == 0);
-      if (IsMutatorActive(heap_state.contexts_disposed, mark_compacts_)) {
-        return kReduceLatency;
-      }
-      break;
-    case kReduceLatency:
-      if (IsMutatorIdle(long_idle_notifications_,
-                        background_idle_notifications_, mutator_gcs)) {
-        return kReduceMemory;
-      }
-      break;
-    case kReduceMemory:
-      if (idle_mark_compacts_ >= kMaxIdleMarkCompacts ||
-          (idle_mark_compacts_ > 0 && !next_gc_likely_to_collect_more_)) {
-        return kDone;
-      }
-      if (mutator_gcs > idle_mark_compacts_) {
-        return kReduceLatency;
-      }
-      break;
-  }
-  return mode_;
-}
 }
 }