cppgc: Port incremental marking schedule

Schedule is simpler compared to the schedule in blink since it now
returns deadlines based on marked bytes instead of time.

If marking is ahead of schedule, return the minimum step size.
Otherwise, set step size to catch up to schedule (ignoring the time
passed while performing the step).
No more default initial step size (needed in blink since marking speed
was unknown).
If estimated schedule is exceeded (marking takes longer than 500ms), the
steps will try to mark all remaining objects but would still be capped
by the maximum step duration of 2ms.

Bug: chromium:1056170
Change-Id: I09857db161c621a12d064f9c8c21b646c34f9d71
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2375200
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69602}

BUILD.gn

@@ -376,7 +376,7 @@ v8_toolset_for_shell = "host"
 #
 
 config("internal_config_base") {
- # Only targets in this file and its subdirs can depend on this.
+  # Only targets in this file and its subdirs can depend on this.
   visibility = [ "./*" ]
 
   configs = [ ":v8_tracing_config" ]
@@ -390,6 +390,7 @@ config("internal_config_base") {
 
 config("internal_config") {
   defines = []
+
   # Only targets in this file and its subdirs can depend on this.
   visibility = [ "./*" ]
 
@@ -4304,6 +4305,8 @@ v8_source_set("cppgc_base") {
     "src/heap/cppgc/heap-visitor.h",
     "src/heap/cppgc/heap.cc",
     "src/heap/cppgc/heap.h",
+    "src/heap/cppgc/incremental-marking-schedule.cc",
+    "src/heap/cppgc/incremental-marking-schedule.h",
     "src/heap/cppgc/liveness-broker.cc",
     "src/heap/cppgc/liveness-broker.h",
     "src/heap/cppgc/logging.cc",

src/heap/cppgc-js/cpp-heap.cc

@@ -137,8 +137,7 @@ void CppHeap::TracePrologue(TraceFlags flags) {
 bool CppHeap::AdvanceTracing(double deadline_in_ms) {
   // TODO(chromium:1056170): Replace std::numeric_limits<size_t>::max() with a
   // proper deadline when unified heap transitions to bytes-based deadline.
-  marking_done_ = marker_->AdvanceMarkingWithDeadline(
-      std::numeric_limits<size_t>::max(),
+  marking_done_ = marker_->AdvanceMarkingWithMaxDuration(
       v8::base::TimeDelta::FromMillisecondsD(deadline_in_ms));
   return marking_done_;
 }

src/heap/cppgc/incremental-marking-schedule.cc

+// Copyright 2020 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/cppgc/incremental-marking-schedule.h"
+
+#include <cmath>
+
+#include "src/heap/cppgc/globals.h"
+
+namespace cppgc {
+namespace internal {
+
+const double IncrementalMarkingSchedule::kEstimatedMarkingTimeMs = 500.0;
+const size_t IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep =
+    64 * kKB;
+
+void IncrementalMarkingSchedule::NotifyIncrementalMarkingStart() {
+  DCHECK(incremental_marking_start_time_.IsNull());
+  incremental_marking_start_time_ = v8::base::TimeTicks::Now();
+}
+
+void IncrementalMarkingSchedule::UpdateIncrementalMarkedBytes(
+    size_t overall_marked_bytes) {
+  DCHECK(!incremental_marking_start_time_.IsNull());
+  incrementally_marked_bytes_ = overall_marked_bytes;
+}
+
+void IncrementalMarkingSchedule::AddConcurrentlyMarkedBytes(
+    size_t marked_bytes) {
+  DCHECK(!incremental_marking_start_time_.IsNull());
+  concurrently_marked_bytes_.fetch_add(marked_bytes, std::memory_order_relaxed);
+}
+
+size_t IncrementalMarkingSchedule::GetOverallMarkedBytes() {
+  return incrementally_marked_bytes_ +
+         concurrently_marked_bytes_.load(std::memory_order_relaxed);
+}
+
+double IncrementalMarkingSchedule::GetElapsedTimeInMs(
+    v8::base::TimeTicks start_time) {
+  if (elapsed_time_for_testing_ != kNoSetElapsedTimeForTesting) {
+    double elapsed_time = elapsed_time_for_testing_;
+    elapsed_time_for_testing_ = kNoSetElapsedTimeForTesting;
+    return elapsed_time;
+  }
+  return (v8::base::TimeTicks::Now() - start_time).InMillisecondsF();
+}
+
+size_t IncrementalMarkingSchedule::GetNextIncrementalStepDuration(
+    size_t estimated_live_bytes) {
+  DCHECK(!incremental_marking_start_time_.IsNull());
+  double elapsed_time_in_ms =
+      GetElapsedTimeInMs(incremental_marking_start_time_);
+  size_t actual_marked_bytes = GetOverallMarkedBytes();
+  size_t expected_marked_bytes = std::ceil(
+      estimated_live_bytes * elapsed_time_in_ms / kEstimatedMarkingTimeMs);
+  if (expected_marked_bytes < actual_marked_bytes) {
+    // Marking is ahead of schedule, incremental marking should do the minimum.
+    return kMinimumMarkedBytesPerIncrementalStep;
+  }
+  // Assuming marking will take |kEstimatedMarkingTime|, overall there will
+  // be |estimated_live_bytes| live bytes to mark, and that marking speed is
+  // constant, after |elapsed_time| the number of marked_bytes should be
+  // |estimated_live_bytes| * (|elapsed_time| / |kEstimatedMarkingTime|),
+  // denoted as |expected_marked_bytes|.  If |actual_marked_bytes| is less,
+  // i.e. marking is behind schedule, incremental marking should help "catch
+  // up" by marking (|expected_marked_bytes| - |actual_marked_bytes|).
+  return std::max(kMinimumMarkedBytesPerIncrementalStep,
+                  expected_marked_bytes - actual_marked_bytes);
+}
+
+}  // namespace internal
+}  // namespace cppgc

src/heap/cppgc/incremental-marking-schedule.h

+// Copyright 2020 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.
+
+#ifndef V8_HEAP_CPPGC_INCREMENTAL_MARKING_SCHEDULE_H_
+#define V8_HEAP_CPPGC_INCREMENTAL_MARKING_SCHEDULE_H_
+
+#include <atomic>
+
+#include "src/base/platform/time.h"
+
+namespace cppgc {
+namespace internal {
+
+class V8_EXPORT_PRIVATE IncrementalMarkingSchedule {
+ public:
+  // Estimated duration of GC cycle in milliseconds.
+  static const double kEstimatedMarkingTimeMs;
+
+  // Minimum number of bytes that should be marked during an incremental
+  // marking step.
+  static const size_t kMinimumMarkedBytesPerIncrementalStep;
+
+  void NotifyIncrementalMarkingStart();
+
+  void UpdateIncrementalMarkedBytes(size_t);
+  void AddConcurrentlyMarkedBytes(size_t);
+
+  size_t GetOverallMarkedBytes();
+
+  size_t GetNextIncrementalStepDuration(size_t);
+
+  void SetElapsedTimeForTesting(double elapsed_time) {
+    elapsed_time_for_testing_ = elapsed_time;
+  }
+
+ private:
+  double GetElapsedTimeInMs(v8::base::TimeTicks);
+
+  v8::base::TimeTicks incremental_marking_start_time_;
+
+  size_t incrementally_marked_bytes_ = 0;
+  std::atomic_size_t concurrently_marked_bytes_{0};
+
+  // Using -1 as sentinel to denote
+  static constexpr double kNoSetElapsedTimeForTesting = -1;
+  double elapsed_time_for_testing_ = kNoSetElapsedTimeForTesting;
+};
+
+}  // namespace internal
+}  // namespace cppgc
+
+#endif  // V8_HEAP_CPPGC_INCREMENTAL_MARKING_SCHEDULE_H_

src/heap/cppgc/marker.cc

@@ -128,6 +128,12 @@ void TraceMarkedObject(Visitor* visitor, const HeapObjectHeader* header) {
   gcinfo.trace(visitor, header->Payload());
 }
 
+size_t GetNextIncrementalStepDuration(IncrementalMarkingSchedule& schedule,
+                                      HeapBase& heap) {
+  return schedule.GetNextIncrementalStepDuration(
+      heap.stats_collector()->allocated_object_size());
+}
+
 }  // namespace
 
 constexpr v8::base::TimeDelta MarkerBase::kMaximumIncrementalStepDuration;
@@ -148,11 +154,8 @@ MarkerBase::IncrementalMarkingTask::Post(v8::TaskRunner* runner,
 void MarkerBase::IncrementalMarkingTask::Run() {
   if (handle_.IsCanceled()) return;
 
-  // TODO(chromium:1056170): Replace hardcoded expected marked bytes with
-  // schedule.
   if (marker_->IncrementalMarkingStep(
-          MarkingConfig::StackState::kNoHeapPointers,
-          kMinimumMarkedBytesPerIncrementalStep)) {
+          MarkingConfig::StackState::kNoHeapPointers)) {
     // Incremental marking is done so should finalize GC.
     marker_->heap().FinalizeIncrementalGarbageCollectionIfNeeded(
         MarkingConfig::StackState::kNoHeapPointers);
@@ -197,6 +200,7 @@ void MarkerBase::StartMarking() {
   is_marking_started_ = true;
   if (EnterIncrementalMarkingIfNeeded(config_, heap())) {
     // Performing incremental or concurrent marking.
+    schedule_.NotifyIncrementalMarkingStart();
     // Scanning the stack is expensive so we only do it at the atomic pause.
     VisitRoots(MarkingConfig::StackState::kNoHeapPointers);
     ScheduleIncrementalMarkingTask();
@@ -224,7 +228,8 @@ void MarkerBase::LeaveAtomicPause() {
   DCHECK(!incremental_marking_handle_);
   ResetRememberedSet(heap());
   heap().stats_collector()->NotifyMarkingCompleted(
-      mutator_marking_state_.marked_bytes());
+      // GetOverallMarkedBytes also includes concurrently marked bytes.
+      schedule_.GetOverallMarkedBytes());
 }
 
 void MarkerBase::FinishMarking(MarkingConfig::StackState stack_state) {
@@ -274,24 +279,21 @@ void MarkerBase::ScheduleIncrementalMarkingTask() {
 }
 
 bool MarkerBase::IncrementalMarkingStepForTesting(
-    MarkingConfig::StackState stack_state, size_t expected_marked_bytes) {
-  return IncrementalMarkingStep(stack_state, expected_marked_bytes);
+    MarkingConfig::StackState stack_state) {
+  return IncrementalMarkingStep(stack_state);
 }
 
-bool MarkerBase::IncrementalMarkingStep(MarkingConfig::StackState stack_state,
-                                        size_t expected_marked_bytes) {
+bool MarkerBase::IncrementalMarkingStep(MarkingConfig::StackState stack_state) {
   if (stack_state == MarkingConfig::StackState::kNoHeapPointers) {
     marking_worklists_.FlushNotFullyConstructedObjects();
   }
   config_.stack_state = stack_state;
 
-  return AdvanceMarkingWithDeadline(expected_marked_bytes);
+  return AdvanceMarkingWithDeadline();
 }
 
 bool MarkerBase::AdvanceMarkingOnAllocation() {
-  // Replace with schedule based deadline.
-  bool is_done =
-      AdvanceMarkingWithDeadline(kMinimumMarkedBytesPerIncrementalStep);
+  bool is_done = AdvanceMarkingWithDeadline();
   if (is_done) {
     // Schedule another incremental task for finalizing without a stack.
     ScheduleIncrementalMarkingTask();
@@ -299,10 +301,15 @@ bool MarkerBase::AdvanceMarkingOnAllocation() {
   return is_done;
 }
 
-bool MarkerBase::AdvanceMarkingWithDeadline(size_t expected_marked_bytes,
-                                            v8::base::TimeDelta max_duration) {
-  bool is_done =
-      ProcessWorklistsWithDeadline(expected_marked_bytes, max_duration);
+bool MarkerBase::AdvanceMarkingWithMaxDuration(
+    v8::base::TimeDelta max_duration) {
+  return AdvanceMarkingWithDeadline(max_duration);
+}
+
+bool MarkerBase::AdvanceMarkingWithDeadline(v8::base::TimeDelta max_duration) {
+  size_t step_size_in_bytes = GetNextIncrementalStepDuration(schedule_, heap_);
+  bool is_done = ProcessWorklistsWithDeadline(step_size_in_bytes, max_duration);
+  schedule_.UpdateIncrementalMarkedBytes(mutator_marking_state_.marked_bytes());
   if (!is_done) {
     // If marking is atomic, |is_done| should always be true.
     DCHECK_NE(MarkingConfig::MarkingType::kAtomic, config_.marking_type);
@@ -316,7 +323,6 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
   size_t marked_bytes_deadline =
       mutator_marking_state_.marked_bytes() + expected_marked_bytes;
   v8::base::TimeTicks time_deadline = v8::base::TimeTicks::Now() + max_duration;
-
   do {
     // Convert |previously_not_fully_constructed_worklist_| to
     // |marking_worklist_|. This merely re-adds items with the proper
@@ -328,8 +334,9 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
               TraceMarkedObject(&visitor(), header);
               mutator_marking_state_.AccountMarkedBytes(*header);
             },
-            MarkingWorklists::kMutatorThreadId))
+            MarkingWorklists::kMutatorThreadId)) {
       return false;
+    }
 
     if (!DrainWorklistWithBytesAndTimeDeadline(
             mutator_marking_state_, marked_bytes_deadline, time_deadline,
@@ -344,8 +351,9 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
               item.callback(&visitor(), item.base_object_payload);
               mutator_marking_state_.AccountMarkedBytes(header);
             },
-            MarkingWorklists::kMutatorThreadId))
+            MarkingWorklists::kMutatorThreadId)) {
       return false;
+    }
 
     if (!DrainWorklistWithBytesAndTimeDeadline(
             mutator_marking_state_, marked_bytes_deadline, time_deadline,
@@ -354,11 +362,11 @@ bool MarkerBase::ProcessWorklistsWithDeadline(
               TraceMarkedObject(&visitor(), header);
               mutator_marking_state_.AccountMarkedBytes(*header);
             },
-            MarkingWorklists::kMutatorThreadId))
+            MarkingWorklists::kMutatorThreadId)) {
       return false;
+    }
   } while (!marking_worklists_.marking_worklist()->IsLocalViewEmpty(
       MarkingWorklists::kMutatorThreadId));
-
   return true;
 }
 

src/heap/cppgc/marker.h

@@ -12,6 +12,7 @@
 #include "src/base/macros.h"
 #include "src/base/platform/time.h"
 #include "src/heap/cppgc/globals.h"
+#include "src/heap/cppgc/incremental-marking-schedule.h"
 #include "src/heap/cppgc/marking-state.h"
 #include "src/heap/cppgc/marking-visitor.h"
 #include "src/heap/cppgc/marking-worklists.h"
@@ -69,8 +70,7 @@ class V8_EXPORT_PRIVATE MarkerBase {
   // Makes marking progress.
   // TODO(chromium:1056170): Remove TimeDelta argument when unified heap no
   // longer uses it.
-  bool AdvanceMarkingWithDeadline(
-      size_t, v8::base::TimeDelta = kMaximumIncrementalStepDuration);
+  bool AdvanceMarkingWithMaxDuration(v8::base::TimeDelta);
 
   // Makes marking progress when allocation a new lab.
   bool AdvanceMarkingOnAllocation();
@@ -97,7 +97,7 @@ class V8_EXPORT_PRIVATE MarkerBase {
   cppgc::Visitor& VisitorForTesting() { return visitor(); }
   void ClearAllWorklistsForTesting();
 
-  bool IncrementalMarkingStepForTesting(MarkingConfig::StackState, size_t);
+  bool IncrementalMarkingStepForTesting(MarkingConfig::StackState);
 
   class IncrementalMarkingTask final : public v8::Task {
    public:
@@ -118,7 +118,6 @@ class V8_EXPORT_PRIVATE MarkerBase {
  protected:
   static constexpr v8::base::TimeDelta kMaximumIncrementalStepDuration =
       v8::base::TimeDelta::FromMilliseconds(2);
-  static constexpr size_t kMinimumMarkedBytesPerIncrementalStep = 64 * kKB;
 
   class Key {
    private:
@@ -136,6 +135,12 @@ class V8_EXPORT_PRIVATE MarkerBase {
   virtual ConservativeTracingVisitor& conservative_visitor() = 0;
   virtual heap::base::StackVisitor& stack_visitor() = 0;
 
+  // Makes marking progress.
+  // TODO(chromium:1056170): Remove TimeDelta argument when unified heap no
+  // longer uses it.
+  bool AdvanceMarkingWithDeadline(
+      v8::base::TimeDelta = kMaximumIncrementalStepDuration);
+
   bool ProcessWorklistsWithDeadline(size_t, v8::base::TimeDelta);
 
   void VisitRoots(MarkingConfig::StackState);
@@ -144,7 +149,7 @@ class V8_EXPORT_PRIVATE MarkerBase {
 
   void ScheduleIncrementalMarkingTask();
 
-  bool IncrementalMarkingStep(MarkingConfig::StackState, size_t);
+  bool IncrementalMarkingStep(MarkingConfig::StackState);
 
   HeapBase& heap_;
   MarkingConfig config_ = MarkingConfig::Default();
@@ -157,6 +162,8 @@ class V8_EXPORT_PRIVATE MarkerBase {
   MarkingState mutator_marking_state_;
   bool is_marking_started_ = false;
 
+  IncrementalMarkingSchedule schedule_;
+
   friend class MarkerFactory;
 };
 

test/unittests/BUILD.gn

@@ -56,6 +56,7 @@ v8_source_set("cppgc_unittests_sources") {
     "heap/cppgc/heap-object-header-unittest.cc",
     "heap/cppgc/heap-page-unittest.cc",
     "heap/cppgc/heap-unittest.cc",
+    "heap/cppgc/incremental-marking-schedule-unittest.cc",
     "heap/cppgc/logging-unittest.cc",
     "heap/cppgc/marker-unittest.cc",
     "heap/cppgc/marking-verifier-unittest.cc",

test/unittests/heap/cppgc/incremental-marking-schedule-unittest.cc

+// Copyright 2020 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/cppgc/incremental-marking-schedule.h"
+
+#include "src/base/platform/time.h"
+#include "src/heap/cppgc/globals.h"
+#include "src/heap/cppgc/stats-collector.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cppgc {
+namespace internal {
+
+namespace {
+
+class IncrementalMarkingScheduleTest : public testing::Test {
+ public:
+  static const size_t kObjectSize;
+};
+
+const size_t IncrementalMarkingScheduleTest::kObjectSize =
+    100 * IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep;
+
+}  // namespace
+
+TEST_F(IncrementalMarkingScheduleTest, FirstStepReturnsDefaultDuration) {
+  IncrementalMarkingSchedule schedule;
+  schedule.NotifyIncrementalMarkingStart();
+  schedule.SetElapsedTimeForTesting(0);
+  EXPECT_EQ(IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+}
+
+// If marking is not behind schedule and very small time passed between steps
+// the oracle should return the minimum step duration.
+TEST_F(IncrementalMarkingScheduleTest, NoTimePassedReturnsMinimumDuration) {
+  IncrementalMarkingSchedule schedule;
+  schedule.NotifyIncrementalMarkingStart();
+  // Add incrementally marked bytes to tell oracle this is not the first step.
+  schedule.UpdateIncrementalMarkedBytes(
+      IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep);
+  schedule.SetElapsedTimeForTesting(0);
+  EXPECT_EQ(IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+}
+
+TEST_F(IncrementalMarkingScheduleTest, OracleDoesntExccedMaximumStepDuration) {
+  IncrementalMarkingSchedule schedule;
+  schedule.NotifyIncrementalMarkingStart();
+  // Add incrementally marked bytes to tell oracle this is not the first step.
+  static constexpr size_t kMarkedBytes = 1;
+  schedule.UpdateIncrementalMarkedBytes(kMarkedBytes);
+  schedule.SetElapsedTimeForTesting(
+      IncrementalMarkingSchedule::kEstimatedMarkingTimeMs);
+  EXPECT_EQ(kObjectSize - kMarkedBytes,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+}
+
+TEST_F(IncrementalMarkingScheduleTest, AheadOfScheduleReturnsMinimumDuration) {
+  IncrementalMarkingSchedule schedule;
+  schedule.NotifyIncrementalMarkingStart();
+  // Add incrementally marked bytes to tell oracle this is not the first step.
+  schedule.UpdateIncrementalMarkedBytes(
+      IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep);
+  schedule.AddConcurrentlyMarkedBytes(0.6 * kObjectSize);
+  schedule.SetElapsedTimeForTesting(
+      0.5 * IncrementalMarkingSchedule::kEstimatedMarkingTimeMs);
+  EXPECT_EQ(IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+}
+
+TEST_F(IncrementalMarkingScheduleTest, BehindScheduleReturnsCorrectDuration) {
+  IncrementalMarkingSchedule schedule;
+  schedule.NotifyIncrementalMarkingStart();
+  schedule.UpdateIncrementalMarkedBytes(0.1 * kObjectSize);
+  schedule.AddConcurrentlyMarkedBytes(0.25 * kObjectSize);
+  schedule.SetElapsedTimeForTesting(
+      0.5 * IncrementalMarkingSchedule::kEstimatedMarkingTimeMs);
+  EXPECT_EQ(0.15 * kObjectSize,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+  schedule.AddConcurrentlyMarkedBytes(0.05 * kObjectSize);
+  schedule.SetElapsedTimeForTesting(
+      0.5 * IncrementalMarkingSchedule::kEstimatedMarkingTimeMs);
+  EXPECT_EQ(0.1 * kObjectSize,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+  schedule.AddConcurrentlyMarkedBytes(0.05 * kObjectSize);
+  schedule.SetElapsedTimeForTesting(
+      0.5 * IncrementalMarkingSchedule::kEstimatedMarkingTimeMs);
+  EXPECT_EQ(0.05 * kObjectSize,
+            schedule.GetNextIncrementalStepDuration(kObjectSize));
+}
+
+}  // namespace internal
+}  // namespace cppgc

test/unittests/heap/cppgc/marker-unittest.cc

@@ -285,7 +285,7 @@ class IncrementalMarkingTest : public testing::TestWithHeap {
       MarkingConfig::MarkingType::kIncremental};
 
   void FinishSteps(MarkingConfig::StackState stack_state) {
-    SingleStep(stack_state, std::numeric_limits<size_t>::max());
+    while (!SingleStep(stack_state)) {}
   }
 
   void FinishMarking() {
@@ -305,9 +305,8 @@ class IncrementalMarkingTest : public testing::TestWithHeap {
   Marker* marker() const { return marker_.get(); }
 
  private:
-  bool SingleStep(MarkingConfig::StackState stack_state, size_t bytes_to_mark) {
-    return marker_->IncrementalMarkingStepForTesting(stack_state,
-                                                     bytes_to_mark);
+  bool SingleStep(MarkingConfig::StackState stack_state) {
+    return marker_->IncrementalMarkingStepForTesting(stack_state);
   }
 
   std::unique_ptr<Marker> marker_;
@@ -380,5 +379,12 @@ TEST_F(IncrementalMarkingTest, IncrementalStepDuringAllocation) {
   FinishMarking();
 }
 
+TEST_F(IncrementalMarkingTest, MarkingRunsOutOfWorkEventually) {
+  InitializeMarker(*Heap::From(GetHeap()), GetPlatformHandle().get(),
+                IncrementalPreciseMarkingConfig);
+  FinishSteps(MarkingConfig::StackState::kNoHeapPointers);
+  FinishMarking();
+}
+
 }  // namespace internal
 }  // namespace cppgc