heap: Add micro benchmark for Member<> write performance

Adds a micro benchmark for Member<> write performance during and outside
of GC. The test can be used to quantify worst-case scenario for the
Member<> write barrier performance. It can be extended to support
different scenarios (e.g., young generation barrier) in future.

Output on a Z840:
[ RUN      ] WriteBarrierPerfTest.MemberWritePerformance
*RESULT WriteBarrierPerfTest writes during GC: = 21781.746896101067 writes/ms
*RESULT WriteBarrierPerfTest writes outside GC: = 476190.4761904762 writes/ms
*RESULT WriteBarrierPerfTest relative speed difference: = 21.861904761904764 times
[       OK ] WriteBarrierPerfTest.MemberWritePerformance (37 ms)

Bug: 1014414
Change-Id: I565564fe3436fbe610c4724d413d4566b289b3fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1862274Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705911}

third_party/blink/renderer/platform/heap/BUILD.gn

@@ -139,6 +139,7 @@ jumbo_source_set("blink_heap_unittests_sources") {
     "persistent_test.cc",
     "thread_state_scheduling_test.cc",
     "worklist_test.cc",
+    "write_barrier_perftest.cc",
   ]
 
   configs += [

third_party/blink/renderer/platform/heap/DEPS

@@ -13,6 +13,7 @@ include_rules = [
     "+base/synchronization/lock.h",
     "+base/task_runner.h",
     "+base/template_util.h",
+    "+testing/perf/perf_test.h",
 
     "+third_party/blink/renderer/platform/bindings",
     "+third_party/blink/renderer/platform/instrumentation/histogram.h",

third_party/blink/renderer/platform/heap/write_barrier_perftest.cc

+// Copyright (c) 2019 The Chromium 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 "base/callback.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/perf/perf_test.h"
+#include "third_party/blink/renderer/platform/heap/heap_test_utilities.h"
+#include "third_party/blink/renderer/platform/heap/persistent.h"
+
+namespace blink {
+
+class WriteBarrierPerfTest : public TestSupportingGC {};
+
+namespace {
+
+class SimpleObject : public GarbageCollected<SimpleObject> {
+ public:
+  SimpleObject() = default;
+  virtual void Trace(Visitor*) {}
+};
+
+base::TimeDelta TimedRun(base::RepeatingCallback<void()> callback) {
+  const base::TimeTicks start = base::TimeTicks::Now();
+  callback.Run();
+  return base::TimeTicks::Now() - start;
+}
+
+}  // namespace
+
+TEST_F(WriteBarrierPerfTest, MemberWritePerformance) {
+  // Setup.
+  constexpr wtf_size_t kNumElements = 100000;
+  Persistent<HeapVector<Member<SimpleObject>>> holder(
+      MakeGarbageCollected<HeapVector<Member<SimpleObject>>>());
+  for (wtf_size_t i = 0; i < kNumElements; ++i) {
+    holder->push_back(MakeGarbageCollected<SimpleObject>());
+  }
+  PreciselyCollectGarbage();
+  // Benchmark.
+  base::RepeatingCallback<void()> benchmark = base::BindRepeating(
+      [](const Persistent<HeapVector<Member<SimpleObject>>>& holder) {
+        for (wtf_size_t i = 0; i < kNumElements / 2; ++i) {
+          (*holder)[i].Swap((*holder)[kNumElements / 2 + i]);
+        }
+      },
+      holder);
+
+  // During GC.
+  IncrementalMarkingTestDriver driver(ThreadState::Current());
+  driver.Start();
+  base::TimeDelta during_gc_duration = TimedRun(benchmark);
+  driver.FinishSteps();
+  PreciselyCollectGarbage();
+
+  // Outside GC.
+  base::TimeDelta outside_gc_duration = TimedRun(benchmark);
+
+  // Cleanup.
+  holder.Clear();
+  PreciselyCollectGarbage();
+
+  // Reporting.
+  perf_test::PrintResult(
+      "WriteBarrierPerfTest", " writes during GC", "",
+      static_cast<double>(kNumElements) / during_gc_duration.InMillisecondsF(),
+      "writes/ms", true);
+  perf_test::PrintResult(
+      "WriteBarrierPerfTest", " writes outside GC", "",
+      static_cast<double>(kNumElements) / outside_gc_duration.InMillisecondsF(),
+      "writes/ms", true);
+  perf_test::PrintResult("WriteBarrierPerfTest", " relative speed difference",
+                         "",
+                         during_gc_duration.InMillisecondsF() /
+                             outside_gc_duration.InMillisecondsF(),
+                         "times", true);
+}
+
+}  // namespace blink