Enable sharding of AllocationRegister on desktop.

base/trace_event/sharded_allocation_register.h

Index: base/trace_event/sharded_allocation_register.h
diff --git a/base/trace_event/sharded_allocation_register.h b/base/trace_event/sharded_allocation_register.h
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+++ b/base/trace_event/sharded_allocation_register.h
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+// Copyright 2017 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_SHARDED_ALLOCATION_REGISTER_H_
+#define BASE_TRACE_EVENT_SHARDED_ALLOCATION_REGISTER_H_
+
+#include <memory>
+#include <unordered_map>
+#include <vector>
+
+#include "base/atomicops.h"
+#include "base/base_export.h"
+#include "base/macros.h"
+#include "base/synchronization/lock.h"
+#include "base/trace_event/heap_profiler_allocation_register.h"
+
+namespace base {
+namespace trace_event {
+
+class TraceEventMemoryOverhead;
+
+// This container holds allocations, and context for each allocation [in the
+// form of a back trace].
+// This container is thread-safe.
+class BASE_EXPORT ShardedAllocationRegister {
+ public:
+  using MetricsMap = std::unordered_map<AllocationContext, AllocationMetrics>;
+
+  struct OutputMetrics {
+    // Total size of allocated objects.
+    size_t size;
+    // Total count of allocated objects.
+    size_t count;
+  };
+
+  ShardedAllocationRegister();
+
+  // This class must be enabled before calling Insert() or Remove(). Once the
+  // class is enabled, it's okay if Insert() or Remove() is called [due to
+  // races] after the class is disabled.
+  void SetEnabled();
+  void SetDisabled();
+  bool is_enabled() const { return !!base::subtle::Acquire_Load(&enabled_); }
+
+  ~ShardedAllocationRegister();
+
+  // Inserts allocation details into the container. If the address was present
+  // already, its details are updated. |address| must not be null.
+  //
+  // Returns true if an insert occurred. Inserts may fail because the table
+  // is full.
+  bool Insert(const void* address,
+              size_t size,
+              const AllocationContext& context);
+
+  // Removes the address from the container if it is present. It is ok to call
+  // this with a null pointer.
+  void Remove(const void* address);
+
+  // Estimates memory overhead including |sizeof(AllocationRegister)|.
+  void EstimateTraceMemoryOverhead(TraceEventMemoryOverhead* overhead) const;
+
+  // Updates |map| with all allocated objects and their statistics.
+  // Returns aggregate statistics.
+  OutputMetrics UpdateAndReturnsMetrics(MetricsMap& map) const;
+
+ private:
+  struct RegisterAndLock {
+    RegisterAndLock();
+    ~RegisterAndLock();
+    AllocationRegister allocation_register;
+    Lock lock;
+  };
+  std::unique_ptr<RegisterAndLock[]> allocation_registers_;
+
+  // This member needs to be checked on every allocation and deallocation [fast
+  // path] when heap profiling is enabled. Using a lock here causes significant
+  // contention.
+  base::subtle::Atomic32 enabled_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShardedAllocationRegister);
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_SHARDED_ALLOCATION_REGISTER_H_