Record Chrome trace events in tcmalloc heap profiles

base/debug/trace_memory.cc

Index: base/debug/trace_memory.cc
diff --git a/base/debug/trace_memory.cc b/base/debug/trace_memory.cc
new file mode 100644
index 0000000000000000000000000000000000000000..65bec56be135a3354ff3e02acf59651c9995c55f
--- /dev/null
+++ b/base/debug/trace_memory.cc
@@ -0,0 +1,236 @@
+// Copyright 2013 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/debug/trace_memory.h"
+
+#include "base/debug/leak_annotations.h"
+#include "base/debug/trace_event.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop.h"
+#include "base/threading/thread_local.h"
+
+// TODO(jamescook): Windows support for memory tracing.
+#if !defined(NO_TCMALLOC) && !defined(OS_NACL) && (defined(OS_LINUX) || defined(OS_ANDROID))

[dsinclair, 2013/06/18 15:30:15]

Could this be done through gyp? Have a trace_memory_stub.cc which is the
NOTREACHED versions and a trace_memory_tcmalloc.cc which is the real version.

Have gyp pick which one we want at build time? (I have no idea if this is
possible/sane, heh)

[James Cook, 2013/06/29 00:02:42]

I think we follow this pattern of using ifdefs other places we interact with the
heap profiler, for example in content/renderer/devtools/devtools_agent.h and in
content/renderer/memory_benchmarking_extension.h

+#include "third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h"
+#endif
+
+namespace base {
+namespace debug {
+
+namespace {
+
+// Maximum number of nested TRACE_MEMORY scopes to record. Must be greater than
+// or equal to HeapProfileTable::kMaxStackDepth.
+const int kMaxStackSize = 32;
+
+/////////////////////////////////////////////////////////////////////////////
+// Holds a memory dump until the tracing system needs to serialize it.
+class MemoryDumpHolder : public base::debug::ConvertableToTraceFormat {
+ public:
+  // Takes ownership of dump, which must be a JSON string, allocated with
+  // malloc() and NULL terminated.
+  explicit MemoryDumpHolder(char* dump) : dump_(dump) {}
+  virtual ~MemoryDumpHolder() { free(dump_); }
+
+  // base::debug::ConvertableToTraceFormat overrides:
+  virtual void AppendAsTraceFormat(std::string* out) const OVERRIDE {
+    out->append(dump_);
+  }
+
+ private:
+  char* dump_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryDumpHolder);
+};
+
+/////////////////////////////////////////////////////////////////////////////
+// Records a stack of TRACE_MEMORY events. One per thread is required.
+struct TraceMemoryStack {
+  TraceMemoryStack() : index_(0) {
+    memset(category_stack_, 0, kMaxStackSize * sizeof(const char*));
+  }
+
+  // Points to the next free entry.
+  int index_;
+  const char* category_stack_[kMaxStackSize];
+};
+
+// One stack of TRACE_MEMORY event data per thread.
+LazyInstance<ThreadLocalPointer<TraceMemoryStack> >::Leaky trace_memory_stack =

[dsinclair, 2013/06/18 15:30:15]

Not sure if it's in the styleguide, but in trace_event_impl.cc we named the
globals as g_trace_memory_stack.

[James Cook, 2013/06/29 00:02:42]

Style guide says it is optional to use g_, but I like it, so done.

+    LAZY_INSTANCE_INITIALIZER;
+
+// Initializes the thread-local trace memory stack and returns it.
+TraceMemoryStack* InitTraceMemoryStack() {
+  DCHECK(!trace_memory_stack.Get().Get());
+  // Intentionally leak one stack per thread.
+  TraceMemoryStack* leaked_stack = new TraceMemoryStack;
+  ANNOTATE_LEAKING_OBJECT_PTR(leaked_stack);
+  trace_memory_stack.Get().Set(leaked_stack);
+  return trace_memory_stack.Get().Get();
+}
+
+// Returns a "pseudo-stack" of pointers to trace events.
+// TODO(jamescook): Record both category and name, perhaps in a pair for speed.
+int GetPseudoStack(void** stack_out) {

[dsinclair, 2013/06/18 15:30:15]

category_stack_ has const char*, why use void* instead of const char*?

+  TraceMemoryStack* stack = trace_memory_stack.Get().Get();
+  // If the tracing system isn't fully initialized, just skip this allocation.
+  // Attempting to initialize will allocate memory, causing this function to
+  // be called recursively from inside the allocator.
+  if (!stack)
+    return 0;
+  // Copy out a maximum of kMaxStackSize stack entries.
+  const int count =
+      stack->index_ < kMaxStackSize ? stack->index_ : kMaxStackSize;
+  // Notes that memcpy() works for zero bytes.
+  memcpy(stack_out, stack->category_stack_, count * sizeof(void*));
+  return count;
+}
+
+// Caller owns the returned char* and must release it with free().
+char* TraceMemoryDumpAsString() {
+#if !defined(NO_TCMALLOC) && !defined(OS_NACL) && (defined(OS_LINUX) || defined(OS_ANDROID))
+  DVLOG(1) << "TraceMemoryDumpAsString";
+  return ::GetHeapProfile();
+#else
+  NOTREACHED();
+  return NULL;
+#endif
+}
+
+// If memory tracing is enabled, dumps a memory profile to the tracing system.
+void DumpMemoryProfile() {
+  DVLOG(1) << "DumpMemoryProfile";
+  // Don't trace allocations here in the memory tracing system.
+  TRACE_MEMORY(TRACE_DISABLED_BY_DEFAULT("memory"), TRACE_MEMORY_IGNORE);
+  // Check to see if tracing is enabled for the memory category.
+  bool enabled;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("memory"),
+                                     &enabled);
+  if (enabled) {
+    // MemoryDumpHolder takes ownership of this string.
+    char* dump = TraceMemoryDumpAsString();
+    scoped_ptr<MemoryDumpHolder> dump_holder(new MemoryDumpHolder(dump));
+    const int kSnapshotId = 1;
+    TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
+        "memory",

[dsinclair, 2013/06/18 15:30:15]

TRACE_DISABLED_BY_DEFAULT("memory") ?

[James Cook, 2013/06/29 00:02:42]

Yes, good catch.

+        "memory::Heap",
+        kSnapshotId,
+        dump_holder.PassAs<base::debug::ConvertableToTraceFormat>());
+  }
+}
+
+void TraceMemoryStart() {
+#if !defined(NO_TCMALLOC) && !defined(OS_NACL) && (defined(OS_LINUX) || defined(OS_ANDROID))
+  DVLOG(1) << "Starting trace memory";
+  // Ensure thread-local-storage is initialized by creating a dummy event.
+  ScopedTraceMemory initialize(TRACE_MEMORY_IGNORE);

[dsinclair, 2013/06/18 15:30:15]

Wouldn't it be easier to get just get the stack and see if it exists and
explicitly initialize here?

Seems weird to create the fake event just to init the stack.

(Or, change InitTraceMemoryStack() to just return if the stack exists then you
can just call it here without doing the get first.)

[James Cook, 2013/06/29 00:02:42]

Changed InitTraceMemoryStack() to GetTraceMemoryStack() which does initialize if
needed, and used it here. That simplified later code too.

+  ::SetPseudoStackGenerator(&GetPseudoStack);
+  ::HeapProfilerStart(NULL);
+#else
+  NOTREACHED();
+#endif
+}
+
+void TraceMemoryStop() {
+#if !defined(NO_TCMALLOC) && !defined(OS_NACL) && (defined(OS_LINUX) || defined(OS_ANDROID))
+  DVLOG(1) << "Stopping trace memory";
+  ::HeapProfilerStop();
+#else
+  NOTREACHED();
+#endif
+}
+
+}  // namespace
+
+//////////////////////////////////////////////////////////////////////////////
+
+TraceMemoryTraceLogObserver::TraceMemoryTraceLogObserver(
+    scoped_refptr<MessageLoopProxy> message_loop_proxy)
+    : message_loop_proxy_(message_loop_proxy),
+      weak_factory_(this) {
+  TraceLog::GetInstance()->AddEnabledStateObserver(this);
+}
+
+TraceMemoryTraceLogObserver::~TraceMemoryTraceLogObserver() {
+  if (dump_timer_.IsRunning())
+    StopProfiling();
+  TraceLog::GetInstance()->RemoveEnabledStateObserver(this);
+}
+
+  // base::debug::TraceLog::EnabledStateChangedObserver overrides:
+void TraceMemoryTraceLogObserver::OnTraceLogEnabled() {
+  DVLOG(1) << "OnTraceLogEnabled";
+  DCHECK(message_loop_proxy_->PostTask(
+      FROM_HERE,
+      base::Bind(&TraceMemoryTraceLogObserver::StartProfiling,
+                 weak_factory_.GetWeakPtr())));
+}
+
+void TraceMemoryTraceLogObserver::OnTraceLogDisabled() {
+  DVLOG(1) << "OnTraceLogDisabled";
+  DCHECK(message_loop_proxy_->PostTask(
+      FROM_HERE,
+      base::Bind(&TraceMemoryTraceLogObserver::StopProfiling,
+                 weak_factory_.GetWeakPtr())));
+}
+
+void TraceMemoryTraceLogObserver::StartProfiling() {
+  TraceMemoryStart();

[dsinclair, 2013/06/18 15:30:15]

Should this do a:

if (dump_timer_.IsRunning())
  return;

Just in case the trace-event framework sends enabled twice?

[James Cook, 2013/06/29 00:02:42]

Good idea. Done.

+  const int kDumpIntervalSeconds = 5;
+  dump_timer_.Start(FROM_HERE,
+                    TimeDelta::FromSeconds(kDumpIntervalSeconds),
+                    base::Bind(&DumpMemoryProfile));
+}
+
+void TraceMemoryTraceLogObserver::StopProfiling() {
+  dump_timer_.Stop();
+  TraceMemoryStop();
+}
+
+bool TraceMemoryTraceLogObserver::IsTimerRunningForTest() const {
+  return dump_timer_.IsRunning();
+}
+
+/////////////////////////////////////////////////////////////////////////////
+
+ScopedTraceMemory::ScopedTraceMemory(const char* category) {
+  // Get our thread's copy of the stack.
+  TraceMemoryStack* stack = trace_memory_stack.Get().Get();
+  if (!stack)
+    stack = InitTraceMemoryStack();

[dsinclair, 2013/06/18 15:30:15]

If InitTraceMemoryStack() always returns this can just become:

TraceMemoryStack* stack = InitTraceMemoryStack();

(Although, maybe then it should be called GetTraceMemoryStack?)

[James Cook, 2013/06/29 00:02:42]

Done.

+  const int index = stack->index_;
+  // Allow deep nesting of stacks (needed for tests), but only record
+  // |kMaxStackSize| entries.
+  if (index < kMaxStackSize)
+    stack->category_stack_[index] = category;
+  stack->index_++;
+}
+
+ScopedTraceMemory::~ScopedTraceMemory() {
+  // Get our thread's copy of the stack.
+  TraceMemoryStack* stack = trace_memory_stack.Get().Get();
+  stack->index_--;
+  DCHECK_GE(stack->index_, 0) << "stack underflow";
+}
+
+// static
+int ScopedTraceMemory::GetStackIndexForTest() {
+  TraceMemoryStack* stack = trace_memory_stack.Get().Get();
+  if (!stack)
+    stack = InitTraceMemoryStack();
+  return stack->index_;
+}
+
+// static
+const char* ScopedTraceMemory::GetItemForTest(int index) {
+  TraceMemoryStack* stack = trace_memory_stack.Get().Get();
+  if (!stack)
+    stack = InitTraceMemoryStack();
+  return stack->category_stack_[index];
+}
+
+}  // namespace debug
+}  // namespace base