blob: 9f64f6ed2fab0f115ffa8f7b137e8a886cdf4abf [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 "base/trace_event/heap_profiler_heap_dump_writer.h"
#include <stdint.h>
#include <algorithm>
#include <iterator>
#include <tuple>
#include <utility>
#include <vector>
#include "base/format_macros.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/strings/stringprintf.h"
#include "base/trace_event/heap_profiler_serialization_state.h"
#include "base/trace_event/heap_profiler_stack_frame_deduplicator.h"
#include "base/trace_event/heap_profiler_type_name_deduplicator.h"
#include "base/trace_event/trace_config.h"
#include "base/trace_event/trace_event.h"
#include "base/trace_event/trace_event_argument.h"
#include "base/trace_event/trace_log.h"
// Most of what the |HeapDumpWriter| does is aggregating detailed information
// about the heap and deciding what to dump. The Input to this process is a list
// of |AllocationContext|s and size pairs.
// The pairs are grouped into |Bucket|s. A bucket is a group of (context, size)
// pairs where the properties of the contexts share a prefix. (Type name is
// considered a list of length one here.) First all pairs are put into one
// bucket that represents the entire heap. Then this bucket is recursively
// broken down into smaller buckets. Each bucket keeps track of whether further
// breakdown is possible.
namespace base {
namespace trace_event {
namespace internal {
namespace {
// Denotes a property of |AllocationContext| to break down by.
enum class BreakDownMode { kByBacktrace, kByTypeName };
// A group of bytes for which the context shares a prefix.
struct Bucket {
: size(0),
is_broken_down_by_type_name(false) {}
std::vector<std::pair<const AllocationContext*, AllocationMetrics>>
// The sum of the sizes of |metrics_by_context|.
size_t size;
// The sum of number of allocations of |metrics_by_context|.
size_t count;
// The index of the stack frame that has not yet been broken down by. For all
// elements in this bucket, the stack frames 0 up to (but not including) the
// cursor, must be equal.
size_t backtrace_cursor;
// When true, the type name for all elements in this bucket must be equal.
bool is_broken_down_by_type_name;
// Comparison operator to order buckets by their size.
bool operator<(const Bucket& lhs, const Bucket& rhs) {
return lhs.size < rhs.size;
// Groups the allocations in the bucket by |break_by|. The buckets in the
// returned list will have |backtrace_cursor| advanced or
// |is_broken_down_by_type_name| set depending on the property to group by.
std::vector<Bucket> GetSubbuckets(const Bucket& bucket,
BreakDownMode break_by) {
std::unordered_map<const void*, Bucket> breakdown;
if (break_by == BreakDownMode::kByBacktrace) {
for (const auto& context_and_metrics : bucket.metrics_by_context) {
const Backtrace& backtrace = context_and_metrics.first->backtrace;
const StackFrame* begin = std::begin(backtrace.frames);
const StackFrame* end = begin + backtrace.frame_count;
const StackFrame* cursor = begin + bucket.backtrace_cursor;
DCHECK_LE(cursor, end);
if (cursor != end) {
Bucket& subbucket = breakdown[cursor->value];
subbucket.size += context_and_metrics.second.size;
subbucket.count += context_and_metrics.second.count;
subbucket.backtrace_cursor = bucket.backtrace_cursor + 1;
subbucket.is_broken_down_by_type_name =
DCHECK_GT(subbucket.size, 0u);
DCHECK_GT(subbucket.count, 0u);
} else if (break_by == BreakDownMode::kByTypeName) {
if (!bucket.is_broken_down_by_type_name) {
for (const auto& context_and_metrics : bucket.metrics_by_context) {
const AllocationContext* context = context_and_metrics.first;
Bucket& subbucket = breakdown[context->type_name];
subbucket.size += context_and_metrics.second.size;
subbucket.count += context_and_metrics.second.count;
subbucket.backtrace_cursor = bucket.backtrace_cursor;
subbucket.is_broken_down_by_type_name = true;
DCHECK_GT(subbucket.size, 0u);
DCHECK_GT(subbucket.count, 0u);
std::vector<Bucket> buckets;
for (auto key_bucket : breakdown)
return buckets;
// Breaks down the bucket by |break_by|. Returns only buckets that contribute
// more than |min_size_bytes| to the total size. The long tail is omitted.
std::vector<Bucket> BreakDownBy(const Bucket& bucket,
BreakDownMode break_by,
size_t min_size_bytes) {
std::vector<Bucket> buckets = GetSubbuckets(bucket, break_by);
// Ensure that |buckets| is a max-heap (the data structure, not memory heap),
// so its front contains the largest bucket. Buckets should be iterated
// ordered by size, but sorting the vector is overkill because the long tail
// of small buckets will be discarded. By using a max-heap, the optimal case
// where all but the first bucket are discarded is O(n). The worst case where
// no bucket is discarded is doing a heap sort, which is O(n log n).
std::make_heap(buckets.begin(), buckets.end());
// Keep including buckets until adding one would increase the number of
// bytes accounted for by |min_size_bytes|. The large buckets end up in
// [it, end()), [begin(), it) is the part that contains the max-heap
// of small buckets.
std::vector<Bucket>::iterator it;
for (it = buckets.end(); it != buckets.begin(); --it) {
if (buckets.front().size < min_size_bytes)
// Put the largest bucket in [begin, it) at |it - 1| and max-heapify
// [begin, it - 1). This puts the next largest bucket at |buckets.front()|.
std::pop_heap(buckets.begin(), it);
// At this point, |buckets| looks like this (numbers are bucket sizes):
// <-- max-heap of small buckets --->
// <-- large buckets by ascending size -->
// [ 19 | 11 | 13 | 7 | 2 | 5 | ... | 83 | 89 | 97 ]
// ^ ^ ^
// | | |
// begin() it end()
// Discard the long tail of buckets that contribute less than a percent.
buckets.erase(buckets.begin(), it);
return buckets;
} // namespace
bool operator<(Entry lhs, Entry rhs) {
// There is no need to compare |size|. If the backtrace and type name are
// equal then the sizes must be equal as well.
return std::tie(lhs.stack_frame_id, lhs.type_id) <
std::tie(rhs.stack_frame_id, rhs.type_id);
HeapDumpWriter::HeapDumpWriter(StackFrameDeduplicator* stack_frame_deduplicator,
TypeNameDeduplicator* type_name_deduplicator,
uint32_t breakdown_threshold_bytes)
: stack_frame_deduplicator_(stack_frame_deduplicator),
breakdown_threshold_bytes_(breakdown_threshold_bytes) {}
HeapDumpWriter::~HeapDumpWriter() {}
bool HeapDumpWriter::AddEntryForBucket(const Bucket& bucket) {
// The contexts in the bucket are all different, but the [begin, cursor) range
// is equal for all contexts in the bucket, and the type names are the same if
// |is_broken_down_by_type_name| is set.
const AllocationContext* context = bucket.metrics_by_context.front().first;
const StackFrame* backtrace_begin = std::begin(context->backtrace.frames);
const StackFrame* backtrace_end = backtrace_begin + bucket.backtrace_cursor;
DCHECK_LE(bucket.backtrace_cursor, arraysize(context->backtrace.frames));
Entry entry;
entry.stack_frame_id =
stack_frame_deduplicator_->Insert(backtrace_begin, backtrace_end);
// Deduplicate the type name, or use ID -1 if type name is not set.
entry.type_id = bucket.is_broken_down_by_type_name
? type_name_deduplicator_->Insert(context->type_name)
: -1;
entry.size = bucket.size;
entry.count = bucket.count;
auto position_and_inserted = entries_.insert(entry);
return position_and_inserted.second;
void HeapDumpWriter::BreakDown(const Bucket& bucket) {
auto by_backtrace = BreakDownBy(bucket, BreakDownMode::kByBacktrace,
auto by_type_name = BreakDownBy(bucket, BreakDownMode::kByTypeName,
// Insert entries for the buckets. If a bucket was not present before, it has
// not been broken down before, so recursively continue breaking down in that
// case. There might be multiple routes to the same entry (first break down
// by type name, then by backtrace, or first by backtrace and then by type),
// so a set is used to avoid dumping and breaking down entries more than once.
for (const Bucket& subbucket : by_backtrace)
if (AddEntryForBucket(subbucket))
for (const Bucket& subbucket : by_type_name)
if (AddEntryForBucket(subbucket))
const std::set<Entry>& HeapDumpWriter::Summarize(
const std::unordered_map<AllocationContext, AllocationMetrics>&
metrics_by_context) {
// Start with one bucket that represents the entire heap. Iterate by
// reference, because the allocation contexts are going to point to allocation
// contexts stored in |metrics_by_context|.
Bucket root_bucket;
for (const auto& context_and_metrics : metrics_by_context) {
DCHECK_GT(context_and_metrics.second.size, 0u);
DCHECK_GT(context_and_metrics.second.count, 0u);
const AllocationContext* context = &context_and_metrics.first;
std::make_pair(context, context_and_metrics.second));
root_bucket.size += context_and_metrics.second.size;
root_bucket.count += context_and_metrics.second.count;
// Recursively break down the heap and fill |entries_| with entries to dump.
return entries_;
std::unique_ptr<TracedValue> Serialize(const std::set<Entry>& entries) {
std::string buffer;
std::unique_ptr<TracedValue> traced_value(new TracedValue);
for (const Entry& entry : entries) {
// Format size as hexadecimal string into |buffer|.
SStringPrintf(&buffer, "%" PRIx64, static_cast<uint64_t>(entry.size));
traced_value->SetString("size", buffer);
SStringPrintf(&buffer, "%" PRIx64, static_cast<uint64_t>(entry.count));
traced_value->SetString("count", buffer);
if (entry.stack_frame_id == -1) {
// An empty backtrace (which will have ID -1) is represented by the empty
// string, because there is no leaf frame to reference in |stackFrames|.
traced_value->SetString("bt", "");
} else {
// Format index of the leaf frame as a string, because |stackFrames| is a
// dictionary, not an array.
SStringPrintf(&buffer, "%i", entry.stack_frame_id);
traced_value->SetString("bt", buffer);
// Type ID -1 (cumulative size for all types) is represented by the absence
// of the "type" key in the dictionary.
if (entry.type_id != -1) {
// Format the type ID as a string.
SStringPrintf(&buffer, "%i", entry.type_id);
traced_value->SetString("type", buffer);
traced_value->EndArray(); // "entries"
return traced_value;
} // namespace internal
std::unique_ptr<TracedValue> ExportHeapDump(
const std::unordered_map<AllocationContext, AllocationMetrics>&
const HeapProfilerSerializationState& heap_profiler_serialization_state) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("memory-infra"), "ExportHeapDump");
internal::HeapDumpWriter writer(
return Serialize(writer.Summarize(metrics_by_context));
} // namespace trace_event
} // namespace base