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// 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_THREAD_HEAP_USAGE_TRACKER_H_
#define BASE_DEBUG_THREAD_HEAP_USAGE_TRACKER_H_
#include <stdint.h>
#include "base/allocator/buildflags.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.
// 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 ThreadHeapUsageTracker {
public:
ThreadHeapUsageTracker();
~ThreadHeapUsageTracker();
// Start tracking heap usage on this thread.
// This may only be called on the thread where the instance is created.
// Note IsHeapTrackingEnabled() must be true.
void Start();
// 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.
// This may only be called on the thread where the instance is created.
void Stop(bool usage_is_exclusive);
// After Stop() returns the usage tallied from Start() to Stop().
const ThreadHeapUsage& usage() const { return usage_; }
// Returns this thread's heap usage from the start of the innermost
// enclosing ThreadHeapUsageTracker instance, if any.
static ThreadHeapUsage GetUsageSnapshot();
// Enables the heap intercept. May only be called once, and only if the heap
// shim is available, e.g. if BUILDFLAG(USE_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 EnsureTLSInitialized();
// Exposed to allow testing the shim without inserting it in the allocator
// shim chain.
static base::allocator::AllocatorDispatch* GetDispatchForTesting();
private:
ThreadChecker thread_checker_;
// The heap usage at Start(), or the difference from Start() to Stop().
ThreadHeapUsage usage_;
// This thread's heap usage, non-null from Start() to Stop().
ThreadHeapUsage* thread_usage_;
};
} // namespace debug
} // namespace base
#endif // BASE_DEBUG_THREAD_HEAP_USAGE_TRACKER_H_
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