blob: 3566dd08f5d377a7f66e5b747c48717723ffb7a5 [file] [log] [blame]
// 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 <stddef.h>
#include <stdint.h>
#include "base/base_export.h"
#include "base/containers/hash_tables.h"
namespace base {
namespace trace_event {
// When heap profiling is enabled, tracing keeps track of the allocation
// context for each allocation intercepted. It is generated by the
// |AllocationContextTracker| which keeps stacks of context in TLS.
// The tracker is initialized lazily.
// The backtrace in the allocation context is a snapshot of the stack. For now,
// this is the pseudo stack where frames are created by trace event macros. In
// the future, we might add the option to use the native call stack. In that
// case, |Backtrace| and |AllocationContextTracker::GetContextSnapshot| might
// have different implementations that can be selected by a compile time flag.
// The number of stack frames stored in the backtrace is a trade off between
// memory used for tracing and accuracy. Measurements done on a prototype
// revealed that:
// - In 60 percent of the cases, pseudo stack depth <= 7.
// - In 87 percent of the cases, pseudo stack depth <= 9.
// - In 95 percent of the cases, pseudo stack depth <= 11.
// See the design doc ( for more details.
// Represents (pseudo) stack frame. Used in Backtrace class below.
// Conceptually stack frame is identified by its value, and type is used
// mostly to properly format the value. Value is expected to be a valid
// pointer from process' address space.
struct BASE_EXPORT StackFrame {
enum class Type {
TRACE_EVENT_NAME, // const char* string
THREAD_NAME, // const char* thread name
PROGRAM_COUNTER, // as returned by stack tracing (e.g. by StackTrace)
static StackFrame FromTraceEventName(const char* name) {
return {Type::TRACE_EVENT_NAME, name};
static StackFrame FromThreadName(const char* name) {
return {Type::THREAD_NAME, name};
static StackFrame FromProgramCounter(const void* pc) {
return {Type::PROGRAM_COUNTER, pc};
Type type;
const void* value;
bool BASE_EXPORT operator < (const StackFrame& lhs, const StackFrame& rhs);
bool BASE_EXPORT operator == (const StackFrame& lhs, const StackFrame& rhs);
bool BASE_EXPORT operator != (const StackFrame& lhs, const StackFrame& rhs);
struct BASE_EXPORT Backtrace {
// If the stack is higher than what can be stored here, the bottom frames
// (the ones closer to main()) are stored. Depth of 12 is enough for most
// pseudo traces (see above), but not for native traces, where we need more.
enum { kMaxFrameCount = 24 };
StackFrame frames[kMaxFrameCount];
size_t frame_count;
bool BASE_EXPORT operator==(const Backtrace& lhs, const Backtrace& rhs);
// The |AllocationContext| is context metadata that is kept for every allocation
// when heap profiling is enabled. To simplify memory management for book-
// keeping, this struct has a fixed size.
struct BASE_EXPORT AllocationContext {
Backtrace backtrace;
// Type name of the type stored in the allocated memory. A null pointer
// indicates "unknown type". Grouping is done by comparing pointers, not by
// deep string comparison. In a component build, where a type name can have a
// string literal in several dynamic libraries, this may distort grouping.
const char* type_name;
bool BASE_EXPORT operator==(const AllocationContext& lhs,
const AllocationContext& rhs);
// Struct to store the size and count of the allocations.
struct AllocationMetrics {
size_t size;
size_t count;
} // namespace trace_event
} // namespace base
template <>
struct BASE_EXPORT hash<base::trace_event::StackFrame> {
size_t operator()(const base::trace_event::StackFrame& frame) const;
template <>
struct BASE_EXPORT hash<base::trace_event::Backtrace> {
size_t operator()(const base::trace_event::Backtrace& backtrace) const;
template <>
struct BASE_EXPORT hash<base::trace_event::AllocationContext> {
size_t operator()(const base::trace_event::AllocationContext& context) const;