[heap] Add IncrementalMarking::AdvanceForTesting bottleneck

Introducing IncrementalMarking::AdvanceForTesting as last bottleneck
for driving incremental marking in addition to AdvanceFromTask
and AdvanceOnAllocation.

Now that we have those 3 bottlenecks, Step() and AdvanceWithDeadline()
can become private methods in IncrementalMarking. We also don't need
the StepResult return value in Step() anymore, which allows us to
remove CombineStepResult.

Bug: v8:12775
Change-Id: I702714439ef7ea4b9abf2156387503d4d00a7a48
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3823131
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82552}

src/heap/heap.cc

@@ -3772,8 +3772,7 @@ void Heap::FinalizeIncrementalMarkingIfComplete(
     GarbageCollectionReason gc_reason) {
   if (incremental_marking()->IsComplete() ||
       (incremental_marking()->IsMarking() &&
-       mark_compact_collector()->local_marking_worklists()->IsEmpty() &&
-       local_embedder_heap_tracer()->ShouldFinalizeIncrementalMarking())) {
+       incremental_marking()->ShouldFinalize())) {
     CollectAllGarbage(current_gc_flags_, gc_reason, current_gc_callback_flags_);
   }
 }

src/heap/incremental-marking.cc

@@ -694,34 +694,58 @@ void IncrementalMarking::ScheduleBytesToMarkBasedOnTime(double time_ms) {
   }
 }
 
-namespace {
-StepResult CombineStepResults(StepResult a, StepResult b) {
-  if (a == StepResult::kMoreWorkRemaining ||
-      b == StepResult::kMoreWorkRemaining)
-    return StepResult::kMoreWorkRemaining;
-  return StepResult::kNoImmediateWork;
+void IncrementalMarking::AdvanceFromTask() {
+  AdvanceWithDeadline(StepOrigin::kTask);
+  heap()->FinalizeIncrementalMarkingIfComplete(
+      GarbageCollectionReason::kFinalizeMarkingViaTask);
 }
-}  // anonymous namespace
 
-StepResult IncrementalMarking::AdvanceWithDeadline(double deadline_in_ms,
-                                                   StepOrigin step_origin) {
+void IncrementalMarking::AdvanceForTesting(double max_step_size_in_ms) {
+  Step(max_step_size_in_ms, StepOrigin::kV8);
+}
+
+void IncrementalMarking::AdvanceOnAllocation() {
+  DCHECK_EQ(heap_->gc_state(), Heap::NOT_IN_GC);
+  DCHECK(FLAG_incremental_marking);
+
+  // Code using an AlwaysAllocateScope assumes that the GC state does not
+  // change; that implies that no marking steps must be performed.
+  if (state_ != MARKING || heap_->always_allocate()) {
+    return;
+  }
+  NestedTimedHistogramScope incremental_marking_scope(
+      heap_->isolate()->counters()->gc_incremental_marking());
+  TRACE_EVENT0("v8", "V8.GCIncrementalMarking");
+  TRACE_GC_EPOCH(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL,
+                 ThreadKind::kMain);
+  ScheduleBytesToMarkBasedOnAllocation();
+  Step(kMaxStepSizeInMs, StepOrigin::kV8);
+}
+
+void IncrementalMarking::AdvanceWithDeadline(StepOrigin step_origin) {
   NestedTimedHistogramScope incremental_marking_scope(
       heap_->isolate()->counters()->gc_incremental_marking());
   TRACE_EVENT1("v8", "V8.GCIncrementalMarking", "epoch",
                heap_->tracer()->CurrentEpoch(GCTracer::Scope::MC_INCREMENTAL));
   TRACE_GC_EPOCH(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL,
                  ThreadKind::kMain);
-  DCHECK(!IsStopped());
+  DCHECK(IsRunning());
 
   ScheduleBytesToMarkBasedOnTime(heap()->MonotonicallyIncreasingTimeInMs());
   FastForwardScheduleIfCloseToFinalization();
-  return Step(kStepSizeInMs, step_origin);
+  Step(kStepSizeInMs, step_origin);
 }
 
-void IncrementalMarking::AdvanceFromTask() {
-  AdvanceWithDeadline(0, StepOrigin::kTask);
-  heap()->FinalizeIncrementalMarkingIfComplete(
-      GarbageCollectionReason::kFinalizeMarkingViaTask);
+bool IncrementalMarking::ShouldFinalize() const {
+  DCHECK(IsRunning());
+
+  return heap()
+             ->mark_compact_collector()
+             ->local_marking_worklists()
+             ->IsEmpty() &&
+         heap()
+             ->local_embedder_heap_tracer()
+             ->ShouldFinalizeIncrementalMarking();
 }
 
 size_t IncrementalMarking::StepSizeToKeepUpWithAllocations() {
@@ -810,27 +834,10 @@ size_t IncrementalMarking::ComputeStepSizeInBytes(StepOrigin step_origin) {
   return scheduled_bytes_to_mark_ - bytes_marked_ - kScheduleMarginInBytes;
 }
 
-void IncrementalMarking::AdvanceOnAllocation() {
-  // Code using an AlwaysAllocateScope assumes that the GC state does not
-  // change; that implies that no marking steps must be performed.
-  if (heap_->gc_state() != Heap::NOT_IN_GC || !FLAG_incremental_marking ||
-      state_ != MARKING || heap_->always_allocate()) {
-    return;
-  }
-  NestedTimedHistogramScope incremental_marking_scope(
-      heap_->isolate()->counters()->gc_incremental_marking());
-  TRACE_EVENT0("v8", "V8.GCIncrementalMarking");
-  TRACE_GC_EPOCH(heap_->tracer(), GCTracer::Scope::MC_INCREMENTAL,
-                 ThreadKind::kMain);
-  ScheduleBytesToMarkBasedOnAllocation();
-  Step(kMaxStepSizeInMs, StepOrigin::kV8);
-}
-
-StepResult IncrementalMarking::Step(double max_step_size_in_ms,
-                                    StepOrigin step_origin) {
+void IncrementalMarking::Step(double max_step_size_in_ms,
+                              StepOrigin step_origin) {
   double start = heap_->MonotonicallyIncreasingTimeInMs();
 
-  StepResult combined_result = StepResult::kMoreWorkRemaining;
   size_t bytes_to_process = 0;
   size_t v8_bytes_processed = 0;
   double embedder_duration = 0.0;
@@ -887,9 +894,9 @@ StepResult IncrementalMarking::Step(double max_step_size_in_ms,
       embedder_result = EmbedderStep(embedder_deadline, &embedder_duration);
     }
     bytes_marked_ += v8_bytes_processed;
-    combined_result = CombineStepResults(v8_result, embedder_result);
 
-    if (combined_result == StepResult::kNoImmediateWork) {
+    if (v8_result == StepResult::kNoImmediateWork &&
+        embedder_result == StepResult::kNoImmediateWork) {
       // TODO(v8:12775): Try to remove.
       FastForwardSchedule();
 
@@ -900,21 +907,23 @@ StepResult IncrementalMarking::Step(double max_step_size_in_ms,
       local_marking_worklists()->ShareWork();
       heap_->concurrent_marking()->RescheduleJobIfNeeded();
     }
+
+    if (FLAG_trace_incremental_marking) {
+      heap_->isolate()->PrintWithTimestamp(
+          "[IncrementalMarking] Step %s V8: %zuKB (%zuKB), embedder: %fms "
+          "(%fms) "
+          "in %.1f\n",
+          step_origin == StepOrigin::kV8 ? "in v8" : "in task",
+          v8_bytes_processed / KB, bytes_to_process / KB, embedder_duration,
+          embedder_deadline, heap_->MonotonicallyIncreasingTimeInMs() - start);
+    }
   }
+
   if (state_ == MARKING) {
     const double v8_duration =
         heap_->MonotonicallyIncreasingTimeInMs() - start - embedder_duration;
     heap_->tracer()->AddIncrementalMarkingStep(v8_duration, v8_bytes_processed);
   }
-  if (FLAG_trace_incremental_marking) {
-    heap_->isolate()->PrintWithTimestamp(
-        "[IncrementalMarking] Step %s V8: %zuKB (%zuKB), embedder: %fms (%fms) "
-        "in %.1f\n",
-        step_origin == StepOrigin::kV8 ? "in v8" : "in task",
-        v8_bytes_processed / KB, bytes_to_process / KB, embedder_duration,
-        embedder_deadline, heap_->MonotonicallyIncreasingTimeInMs() - start);
-  }
-  return combined_result;
 }
 
 }  // namespace internal

src/heap/incremental-marking.h

@@ -109,6 +109,8 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
     return collection_requested_via_stack_guard_;
   }
 
+  bool ShouldFinalize() const;
+
   bool CanBeStarted() const;
 
   void Start(GarbageCollectionReason gc_reason);
@@ -118,11 +120,6 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
   void UpdateMarkingWorklistAfterYoungGenGC();
   void UpdateMarkedBytesAfterScavenge(size_t dead_bytes_in_new_space);
 
-  // Performs incremental marking steps and returns before the deadline_in_ms is
-  // reached. It may return earlier if the marker is already ahead of the
-  // marking schedule, which is indicated with StepResult::kDone.
-  StepResult AdvanceWithDeadline(double deadline_in_ms, StepOrigin step_origin);
-
   // Performs incremental marking step and finalizes marking if complete.
   void AdvanceFromTask();
 
@@ -130,8 +127,6 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
   // marking completes.
   void AdvanceOnAllocation();
 
-  StepResult Step(double max_step_size_in_ms, StepOrigin step_origin);
-
   // This function is used to color the object black before it undergoes an
   // unsafe layout change. This is a part of synchronization protocol with
   // the concurrent marker.
@@ -162,6 +157,9 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
 
   void MarkRootsForTesting();
 
+  // Performs incremental marking step for unit tests.
+  void AdvanceForTesting(double max_step_size_in_ms);
+
  private:
   class IncrementalMarkingRootMarkingVisitor;
 
@@ -219,6 +217,13 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
 
   void MarkRoots();
 
+  // Performs incremental marking steps and returns before the deadline_in_ms is
+  // reached. It may return earlier if the marker is already ahead of the
+  // marking schedule, which is indicated with StepResult::kDone.
+  void AdvanceWithDeadline(StepOrigin step_origin);
+
+  void Step(double max_step_size_in_ms, StepOrigin step_origin);
+
   // Returns true if the function succeeds in transitioning the object
   // from white to grey.
   bool WhiteToGreyAndPush(HeapObject obj);

test/cctest/heap/heap-utils.cc

@@ -190,8 +190,9 @@ void SimulateIncrementalMarking(i::Heap* heap, bool force_completion) {
   marking->MarkRootsForTesting();
 
   while (!marking->IsComplete()) {
-    marking->Step(kStepSizeInMs, i::StepOrigin::kV8);
+    marking->AdvanceForTesting(kStepSizeInMs);
   }
+
   CHECK(marking->IsComplete());
 }
 

test/cctest/heap/test-heap.cc

@@ -2480,10 +2480,11 @@ TEST(InstanceOfStubWriteBarrier) {
   MarkingState* marking_state = marking->marking_state();
 
   const double kStepSizeInMs = 100;
-  while (!marking_state->IsBlack(f->code()) && !marking->IsStopped()) {
+  while (!marking_state->IsBlack(f->code())) {
     // Discard any pending GC requests otherwise we will get GC when we enter
     // code below.
-    marking->Step(kStepSizeInMs, StepOrigin::kV8);
+    CHECK(!marking->IsComplete());
+    marking->AdvanceForTesting(kStepSizeInMs);
   }
 
   CHECK(marking->IsMarking());
@@ -2576,12 +2577,9 @@ TEST(IdleNotificationFinishMarking) {
   CHECK_EQ(CcTest::heap()->gc_count(), initial_gc_count);
 
   const double kStepSizeInMs = 100;
-  do {
-    marking->Step(kStepSizeInMs, StepOrigin::kV8);
-  } while (!CcTest::heap()
-                ->mark_compact_collector()
-                ->local_marking_worklists()
-                ->IsEmpty());
+  while (!marking->IsComplete()) {
+    marking->AdvanceForTesting(kStepSizeInMs);
+  }
 
   // The next idle notification has to finish incremental marking.
   const double kLongIdleTime = 1000.0;
@@ -5775,7 +5773,7 @@ TEST(Regress598319) {
   // only partially marked the large object.
   const double kSmallStepSizeInMs = 0.1;
   while (!marking->IsComplete()) {
-    marking->Step(kSmallStepSizeInMs, StepOrigin::kV8);
+    marking->AdvanceForTesting(kSmallStepSizeInMs);
     ProgressBar& progress_bar = page->ProgressBar();
     if (progress_bar.IsEnabled() && progress_bar.Value() > 0) {
       CHECK_NE(progress_bar.Value(), arr.get().Size());
@@ -5797,7 +5795,7 @@ TEST(Regress598319) {
   // Finish marking with bigger steps to speed up test.
   const double kLargeStepSizeInMs = 1000;
   while (!marking->IsComplete()) {
-    marking->Step(kLargeStepSizeInMs, StepOrigin::kV8);
+    marking->AdvanceForTesting(kLargeStepSizeInMs);
   }
   CHECK(marking->IsComplete());
 
@@ -5885,7 +5883,7 @@ TEST(Regress615489) {
   }
   const double kStepSizeInMs = 100;
   while (!marking->IsComplete()) {
-    marking->Step(kStepSizeInMs, StepOrigin::kV8);
+    marking->AdvanceForTesting(kStepSizeInMs);
   }
   CHECK(marking->IsComplete());
   intptr_t size_before = heap->SizeOfObjects();
@@ -5943,7 +5941,7 @@ TEST(Regress631969) {
   const double kStepSizeInMs = 100;
   IncrementalMarking* marking = heap->incremental_marking();
   while (!marking->IsComplete()) {
-    marking->Step(kStepSizeInMs, StepOrigin::kV8);
+    marking->AdvanceForTesting(kStepSizeInMs);
   }
 
   {
@@ -6520,8 +6518,8 @@ HEAP_TEST(Regress670675) {
                                         AllocationType::kOld);
     }
     if (marking->IsStopped()) break;
-    double deadline = heap->MonotonicallyIncreasingTimeInMs() + 1;
-    marking->AdvanceWithDeadline(deadline, StepOrigin::kV8);
+    const double kStepSizeInMs = 1.0;
+    marking->AdvanceForTesting(kStepSizeInMs);
   }
   DCHECK(marking->IsStopped());
 }

test/unittests/heap/heap-utils.cc

@@ -31,7 +31,7 @@ void HeapInternalsBase::SimulateIncrementalMarking(Heap* heap,
   if (!force_completion) return;
 
   while (!marking->IsComplete()) {
-    marking->Step(kStepSizeInMs, i::StepOrigin::kV8);
+    marking->AdvanceForTesting(kStepSizeInMs);
   }
   CHECK(marking->IsComplete());
 }