[tracing] Ignore tracing allocations in heap profiler

base/trace_event/heap_profiler.h

+// Copyright 2016 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.
+
+#ifndef BASE_TRACE_EVENT_HEAP_PROFILER_H
+#define BASE_TRACE_EVENT_HEAP_PROFILER_H
+
+#include "base/compiler_specific.h"
+#include "base/trace_event/heap_profiler_allocation_context_tracker.h"
+
+// This header file defines the set of macros that are used to track memory
+// usage in the heap profiler. This is in addition to the macros defined in
+// trace_event.h and are specific to heap profiler. This file also defines
+// implementation details of these macros.
+
+// Implementation detail: heap profiler macros create temporary variables to
+// keep instrumentation overhead low. These macros give each temporary variable
+// a unique name based on the line number to prevent name collisions.
+#define INTERNAL_HEAP_PROFILER_UID3(a, b) heap_profiler_unique_##a##b
+#define INTERNAL_HEAP_PROFILER_UID2(a, b) INTERNAL_HEAP_PROFILER_UID3(a, b)
+#define INTERNAL_HEAP_PROFILER_UID(name_prefix) \
+  INTERNAL_HEAP_PROFILER_UID2(name_prefix, __LINE__)
+
+// A scoped ignore event used to tell heap profiler to ignore all the
+// allocations in the scope. It is useful to exclude allocations made for
+// tracing from the heap profiler dumps.
+#define HEAP_PROFILER_SCOPED_IGNORE                                          \
+  trace_event_internal::HeapProfilerScopedIgnore INTERNAL_HEAP_PROFILER_UID( \
+      scoped_ignore)
+
+namespace trace_event_internal {
+
+class BASE_EXPORT HeapProfilerScopedIgnore {
+ public:
+  inline HeapProfilerScopedIgnore() {
+    if (UNLIKELY(
+            base::trace_event::AllocationContextTracker::capture_enabled())) {
+      base::trace_event::AllocationContextTracker::GetInstanceForCurrentThread()
+          ->begin_ignore_scope();
+    }
+  }
+  inline ~HeapProfilerScopedIgnore() {
+    if (UNLIKELY(
+            base::trace_event::AllocationContextTracker::capture_enabled())) {
+      base::trace_event::AllocationContextTracker::GetInstanceForCurrentThread()
+          ->end_ignore_scope();
+    }
+  }
+};
+
+}  // namespace trace_event_internal
+
+#endif  // BASE_TRACE_EVENT_HEAP_PROFILER_H