[heap] GCTracer: Record details for incremental marking

test/unittests/heap/gc-tracer-unittest.cc

Index: test/unittests/heap/gc-tracer-unittest.cc
diff --git a/test/unittests/heap/gc-tracer-unittest.cc b/test/unittests/heap/gc-tracer-unittest.cc
index 97975d488bbfe5bb8720b080d1dc57289656630a..84e4d973e215709e9602ff9e193abaf7c773f082 100644
--- a/test/unittests/heap/gc-tracer-unittest.cc
+++ b/test/unittests/heap/gc-tracer-unittest.cc
@@ -183,5 +183,57 @@ TEST_F(GCTracerTest, IncrementalScope) {
       200.0, tracer->current_.scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]);
 }
 
+TEST_F(GCTracerTest, IncrementalMarkingDetails) {
+  GCTracer* tracer = i_isolate()->heap()->tracer();
+  tracer->ResetForTesting();
+
+  // Round 1.
+  tracer->AddScopeSample(GCTracer::Scope::MC_INCREMENTAL_FINALIZE, 50);
+  tracer->Start(MARK_COMPACTOR, "gc unittest", "collector unittest");
+  // Switch to incremental MC to enable writing back incremental scopes.
+  tracer->current_.type = GCTracer::Event::INCREMENTAL_MARK_COMPACTOR;
+  tracer->AddScopeSample(GCTracer::Scope::MC_INCREMENTAL_FINALIZE, 100);
+  tracer->Stop(MARK_COMPACTOR);
+  EXPECT_DOUBLE_EQ(
+      100,
+      tracer->current_
+          .incremental_marking_scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]
+          .longest_step);
+  EXPECT_EQ(
+      2,
+      tracer->current_
+          .incremental_marking_scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]
+          .steps);
+  EXPECT_DOUBLE_EQ(
+      150,
+      tracer->current_
+          .incremental_marking_scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]
+          .cumulative_duration);
+
+  // Round 2. Cumulative numbers should add up, others should be reset.
+  tracer->AddScopeSample(GCTracer::Scope::MC_INCREMENTAL_FINALIZE, 13);
+  tracer->AddScopeSample(GCTracer::Scope::MC_INCREMENTAL_FINALIZE, 15);
+  tracer->Start(MARK_COMPACTOR, "gc unittest", "collector unittest");
+  // Switch to incremental MC to enable writing back incremental scopes.
+  tracer->current_.type = GCTracer::Event::INCREMENTAL_MARK_COMPACTOR;
+  tracer->AddScopeSample(GCTracer::Scope::MC_INCREMENTAL_FINALIZE, 122);
+  tracer->Stop(MARK_COMPACTOR);
+  EXPECT_DOUBLE_EQ(
+      122,
+      tracer->current_
+          .incremental_marking_scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]
+          .longest_step);
+  EXPECT_EQ(
+      3,
+      tracer->current_
+          .incremental_marking_scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]
+          .steps);
+  EXPECT_DOUBLE_EQ(
+      300,
+      tracer->current_
+          .incremental_marking_scopes[GCTracer::Scope::MC_INCREMENTAL_FINALIZE]
+          .cumulative_duration);
+}
+
 }  // namespace internal
 }  // namespace v8