Rename ScopedThreadHeapUsage to ThreadHeapUsageTracker.

base/debug/thread_heap_usage_tracker.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_DEBUG_SCOPED_THREAD_HEAP_USAGE_H_
-#define BASE_DEBUG_SCOPED_THREAD_HEAP_USAGE_H_
+#ifndef BASE_DEBUG_THREAD_HEAP_USAGE_TRACKER_H_
+#define BASE_DEBUG_THREAD_HEAP_USAGE_TRACKER_H_
 
 #include <stdint.h>
 
 #include "base/allocator/features.h"
 #include "base/base_export.h"
 #include "base/threading/thread_checker.h"
 
 namespace base {
 namespace allocator {
 struct AllocatorDispatch;
 }  // namespace allocator
 
 namespace debug {
 
+// Used to store the heap allocator usage in a scope.
+struct ThreadHeapUsage {
+  // The cumulative number of allocation operations.
+  uint64_t alloc_ops;
+
+  // The cumulative number of allocated bytes. Where available, this is
+  // inclusive heap padding and estimated or actual heap overhead.
+  uint64_t alloc_bytes;
+
+  // Where available, cumulative number of heap padding and overhead bytes.
+  uint64_t alloc_overhead_bytes;
+
+  // The cumulative number of free operations.
+  uint64_t free_ops;
+
+  // The cumulative number of bytes freed.
+  // Only recorded if the underlying heap shim can return the size of an
+  // allocation.
+  uint64_t free_bytes;
+
+  // The maximal value of alloc_bytes - free_bytes seen for this thread.

[Lei Zhang, 2016/10/17 20:54:23]

nit: |alloc_bytes|, |free_bytes|

[Sigurður Ásgeirsson, 2016/10/18 13:39:23]

Done.

+  // Only recorded if the underlying heap shim supports returning the size of
+  // an allocation.
+  uint64_t max_allocated_bytes;
+};
+
 // By keeping a tally on heap operations, it's possible to track:
 // - the number of alloc/free operations, where a realloc is zero or one
 //   of each, depending on the input parameters (see man realloc).
 // - the number of bytes allocated/freed.
 // - the number of estimated bytes of heap overhead used.
 // - the high-watermark amount of bytes allocated in the scope.
 // This in turn allows measuring the memory usage and memory usage churn over
 // a scope. Scopes must be cleanly nested, and each scope must be
 // destroyed on the thread where it's created.
 //
 // Note that this depends on the capabilities of the underlying heap shim. If
 // that shim can not yield a size estimate for an allocation, it's not possible
 // to keep track of overhead, freed bytes and the allocation high water mark.
-class BASE_EXPORT ScopedThreadHeapUsage {
+class BASE_EXPORT ThreadHeapUsageTracker {
  public:
-  struct ThreadAllocatorUsage {
-    // The cumulative number of allocation operations.
-    uint64_t alloc_ops;
+  ThreadHeapUsageTracker();
+  ~ThreadHeapUsageTracker();
 
-    // The cumulative number of allocated bytes. Where available, this is
-    // inclusive heap padding and estimated or actual heap overhead.
-    uint64_t alloc_bytes;
+  // Start tracking heap usage on this thread.
+  // Note |IsHeapTrackingEnabled()| must be true.

[Lei Zhang, 2016/10/17 20:54:23]

And IsHeapTrackingEnabled() is not a variable.

[Sigurður Ásgeirsson, 2016/10/18 13:39:23]

Done.

+  void Start();
 
-    // Where available, cumulative number of heap padding heap
-    // and overhead bytes.
-    uint64_t alloc_overhead_bytes;
+  // Stop tracking heap usage on this thread and store the usage tallied.
+  // If |usage_is_exclusive| is true, the usage tallied won't be added to the
+  // outer scope's usage. If |usage_is_exclusive| is false, the usage tallied
+  // in this scope will also tally to any outer scope.
+  void Stop(bool usage_is_exclusive);
 
-    // The cumulative number of free operations.
-    uint64_t free_ops;
+  // After Stop() returns the usage tallied from Start() to Stop().
+  const ThreadHeapUsage& usage() const { return usage_; }
 
-    // The cumulative number of bytes freed.
-    // Only recorded if the underlying heap shim can return the size of an
-    // allocation.
-    uint64_t free_bytes;
-
-    // The maximal value of alloc_bytes - free_bytes seen for this thread.
-    // Only recorded if the underlying heap shim supports returning the size of
-    // an allocation.
-    uint64_t max_allocated_bytes;
-  };
-
-  ScopedThreadHeapUsage();
-  ~ScopedThreadHeapUsage();
-
-  const ThreadAllocatorUsage& usage_at_creation() const {
-    return usage_at_creation_;
-  }
-
-  // Returns this thread's allocator usage from the creation of the innermost
-  // enclosing ScopedThreadHeapUsage instance, if any. Note that this is
-  // inclusive allocator usage in all inner scopes.
-  static ThreadAllocatorUsage CurrentUsage();
-
-  // Initializes the TLS machinery this class uses. Must be called before
-  // creating instances of this class.
-  static void Initialize();
+  // Returns this thread's allocator usage from the start of the innermost
+  // enclosing ThreadHeapUsageTracker instance, if any.
+  static ThreadHeapUsage CurrentUsage();
 
   // Enables the heap intercept. May only be called once, and only if the heap
   // shim is available, e.g. if BUILDFLAG(USE_EXPERIMENTAL_ALLOCATOR_SHIM) is
   // true.
   static void EnableHeapTracking();
 
+  // Returns true iff heap tracking is enabled.
+  static bool IsHeapTrackingEnabled();
+
  protected:
   // Exposed for testing only - note that it's safe to re-EnableHeapTracking()
   // after calling this function in tests.
   static void DisableHeapTrackingForTesting();
 
+  // Exposed for testing only.
+  static void EnsureTLSInitializedForTesting();
+
   // Exposed to allow testing the shim without inserting it in the allocator
   // shim chain.
   static base::allocator::AllocatorDispatch* GetDispatchForTesting();
 
  private:
   static void EnsureTLSInitialized();
 
   ThreadChecker thread_checker_;
-  // The allocator usage captured at creation of this instance.
-  ThreadAllocatorUsage usage_at_creation_;
+
+  // The allocator usage at Start(), or the difference from Start() to Stop().
+  ThreadHeapUsage usage_;
+
+  // This thread's allocator usage, non-null from Start() to Stop().
+  ThreadHeapUsage* thread_usage_;
 };
 
 }  // namespace debug
 }  // namespace base
 
-#endif  // BASE_DEBUG_SCOPED_THREAD_HEAP_USAGE_H_
+#endif  // BASE_DEBUG_THREAD_HEAP_USAGE_TRACKER_H_