[tracing] Adding task information to heap profiler

base/trace_event/heap_profiler_allocation_context_tracker.cc

 // Copyright 2015 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/trace_event/heap_profiler_allocation_context_tracker.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/atomicops.h"
+#include "base/compiler_specific.h"
 #include "base/threading/thread_local_storage.h"
 #include "base/trace_event/heap_profiler_allocation_context.h"
 
 namespace base {
 namespace trace_event {
 
 subtle::Atomic32 AllocationContextTracker::capture_enabled_ = 0;
 
 namespace {
 
 const size_t kMaxStackDepth = 128u;
+const size_t kMaxTaskDepth = 16u;
 AllocationContextTracker* const kInitializingSentinel =
     reinterpret_cast<AllocationContextTracker*>(-1);
 
 ThreadLocalStorage::StaticSlot g_tls_alloc_ctx_tracker = TLS_INITIALIZER;
 
 // This function is added to the TLS slot to clean up the instance when the
 // thread exits.
 void DestructAllocationContextTracker(void* alloc_ctx_tracker) {
   delete static_cast<AllocationContextTracker*>(alloc_ctx_tracker);
 }
 
 }  // namespace
 
+AllocationContextTracker::ScopedTaskExecutionEvent::ScopedTaskExecutionEvent(
+    const char* category_group,
+    const char* posted_reason)
+    : category_(category_group) {
+  if (UNLIKELY(capture_enabled())) {
+    AllocationContextTracker* tracker = GetInstanceForCurrentThread();
+    tracker->PushCurrentCategoryName(category_);
+  }
+}
+
+AllocationContextTracker::ScopedTaskExecutionEvent::
+    ~ScopedTaskExecutionEvent() {
+  if (UNLIKELY(capture_enabled())) {
+    AllocationContextTracker* tracker = GetInstanceForCurrentThread();
+    tracker->PopCurrentCategoryName(category_);
+  }
+}
+
 // static
 AllocationContextTracker*
 AllocationContextTracker::GetInstanceForCurrentThread() {
   AllocationContextTracker* tracker =
       static_cast<AllocationContextTracker*>(g_tls_alloc_ctx_tracker.Get());
   if (tracker == kInitializingSentinel)
     return nullptr;  // Re-entrancy case.
 
   if (!tracker) {
     g_tls_alloc_ctx_tracker.Set(kInitializingSentinel);
     tracker = new AllocationContextTracker();
     g_tls_alloc_ctx_tracker.Set(tracker);
   }
 
   return tracker;
 }
 
 AllocationContextTracker::AllocationContextTracker() {
   pseudo_stack_.reserve(kMaxStackDepth);
+  categories_.reserve(kMaxTaskDepth);
 }
 AllocationContextTracker::~AllocationContextTracker() {}
 
 // static
 void AllocationContextTracker::SetCaptureEnabled(bool enabled) {
   // When enabling capturing, also initialize the TLS slot. This does not create
   // a TLS instance yet.
   if (enabled && !g_tls_alloc_ctx_tracker.initialized())
     g_tls_alloc_ctx_tracker.Initialize(DestructAllocationContextTracker);
 
@@ skipping 51 matching lines @@
 
     // Copy as much of the bottom of the pseudo stack into the backtrace as
     // possible.
     for (; src != src_end && dst != dst_end; src++, dst++)
       *dst = *src;
 
     // If there is room for more, fill the remaining slots with empty frames.
     std::fill(dst, dst_end, nullptr);
   }
 
-  ctx.type_name = nullptr;
+  // Set the default type name to file name where the task was posted from.
+  // TODO(ssid): Fix crbug.com/594803 to add file name as 3rd dimension
+  // (component name) in the heap profiler and not piggy back on the type name.
+  ctx.type_name = categories_.empty() ? nullptr : categories_.back();
 
   return ctx;
 }
 
+void AllocationContextTracker::PushCurrentCategoryName(const char* category) {
+  DCHECK(category != nullptr);

[Primiano Tucci (use gerrit), 2016/03/25 01:56:31]

I think as a general stylistic pattern we don't bother with != nullptr, just
DCHECK(category) should be file.
Also rename the arg :) 

[ssid, 2016/03/28 18:14:49]

Done.

+  if (categories_.size() < kMaxTaskDepth)
+    categories_.push_back(category);
+  else
+    NOTREACHED();
+}
+
+void AllocationContextTracker::PopCurrentCategoryName(const char* category) {
+  DCHECK_EQ(category, categories_.back())
+      << "Encountered an unmatched category end";
+  categories_.pop_back();
+}
+
 }  // namespace trace_event
 }  // namespace base