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// 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 "components/metrics/call_stack_profile_metrics_provider.h"
#include <algorithm>
#include <iterator>
#include <utility>
#include <vector>
#include "base/bind.h"
#include "base/macros.h"
#include "base/no_destructor.h"
#include "base/synchronization/lock.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "third_party/metrics_proto/chrome_user_metrics_extension.pb.h"
namespace metrics {
namespace {
// Cap the number of pending profiles to avoid excessive memory usage when
// profile uploads are delayed (e.g. due to being offline). 1250 profiles
// corresponds to 80MB of storage. Capping at this threshold loses approximately
// 0.5% of profiles on canary and dev.
// TODO(chengx): Remove this threshold after moving to a more memory-efficient
// profile representation.
const size_t kMaxPendingProfiles = 1250;
// Cap the number of pending unserialized profiles to avoid excessive memory
// usage when profile uploads are delayed (e.g., due to being offline). When the
// number of pending unserialized profiles exceeds this cap, serialize all
// additional unserialized profiles to save memory. Since profile serialization
// and deserialization (required later for uploads) are expensive, we choose 250
// as the capacity to balance speed and memory. 250 unserialized profiles
// corresponds to 16MB of storage.
// TODO(chengx): Remove this threshold after moving to a more memory-efficient
// profile representation.
constexpr size_t kMaxPendingUnserializedProfiles = 250;
// Merges the serialized profiles into the unserialized ones, by appending them.
// The params are not const& because they should be passed using std::move.
// Implementation note: In order to maintain the invariant that profiles are
// reported in correct temporal sequence, it's important to order the serialized
// profiles to follow the unserialized profiles. This way, profiles that were
// serialized simply for space efficiency will end up ordered correctly.
std::vector<SampledProfile> MergeProfiles(
std::vector<SampledProfile> profiles,
std::vector<std::string> serialized_profiles) {
// Deserialize all serialized profiles, skipping over any that fail to parse.
std::vector<SampledProfile> deserialized_profiles;
for (const auto& serialized_profile : serialized_profiles) {
SampledProfile profile;
if (profile.ParseFromArray(,
serialized_profile.size())) {
// Merge the profiles.
profiles.reserve(profiles.size() + deserialized_profiles.size());
std::move(deserialized_profiles.begin(), deserialized_profiles.end(),
return profiles;
// PendingProfiles ------------------------------------------------------------
// Singleton class responsible for retaining profiles received from
// CallStackProfileBuilder. These are then sent to UMA on the invocation of
// CallStackProfileMetricsProvider::ProvideCurrentSessionData(). We need to
// store the profiles outside of a CallStackProfileMetricsProvider instance
// since callers may start profiling before the CallStackProfileMetricsProvider
// is created.
// Member functions on this class may be called on any thread.
class PendingProfiles {
static PendingProfiles* GetInstance();
// Retrieves all the pending profiles.
std::vector<SampledProfile> RetrieveProfiles();
// Enables the collection of profiles by MaybeCollect*Profile if |enabled| is
// true. Otherwise, clears the currently collected profiles and ignores
// profiles provided to future invocations of MaybeCollect*Profile.
void SetCollectionEnabled(bool enabled);
// Collects |profile|. It may be stored as it is, or in a serialized form, or
// ignored, depending on the pre-defined storage capacity and whether
// collection is enabled. |profile| is not const& because it must be passed
// with std::move.
void MaybeCollectProfile(base::TimeTicks profile_start_time,
SampledProfile profile);
// Collects |serialized_profile|. It may be ignored depending on the
// pre-defined storage capacity and whether collection is enabled.
// |serialized_profile| is not const& because it must be passed with
// std::move.
void MaybeCollectSerializedProfile(base::TimeTicks profile_start_time,
std::string serialized_profile);
// Allows testing against the initial state multiple times.
void ResetToDefaultStateForTesting();
friend class base::NoDestructor<PendingProfiles>;
~PendingProfiles() = delete;
// Returns true if collection is enabled for a given profile based on its
// |profile_start_time|. The |lock_| must be held prior to calling this
// method.
bool IsCollectionEnabledForProfile(base::TimeTicks profile_start_time) const
// Whether there is spare capacity to store an additional profile.
// The |lock_| must be held prior to calling this method.
bool HasSpareCapacity() const EXCLUSIVE_LOCKS_REQUIRED(lock_);
mutable base::Lock lock_;
// If true, profiles provided to MaybeCollect*Profile should be collected.
// Otherwise they will be ignored.
bool collection_enabled_ GUARDED_BY(lock_);
// The last time collection was disabled. Used to determine if collection was
// disabled at any point since a profile was started.
base::TimeTicks last_collection_disable_time_ GUARDED_BY(lock_);
// The last time collection was enabled. Used to determine if collection was
// enabled at any point since a profile was started.
base::TimeTicks last_collection_enable_time_ GUARDED_BY(lock_);
// The set of completed unserialized profiles that should be reported.
std::vector<SampledProfile> unserialized_profiles_ GUARDED_BY(lock_);
// The set of completed serialized profiles that should be reported.
std::vector<std::string> serialized_profiles_ GUARDED_BY(lock_);
// static
PendingProfiles* PendingProfiles::GetInstance() {
// Singleton for performance rather than correctness reasons.
static base::NoDestructor<PendingProfiles> instance;
return instance.get();
std::vector<SampledProfile> PendingProfiles::RetrieveProfiles() {
std::vector<SampledProfile> profiles;
std::vector<std::string> serialized_profiles;
base::AutoLock scoped_lock(lock_);
// Merge the serialized profiles by deserializing them. Note that this work is
// performed without holding the lock, to avoid blocking the lock for an
// extended period of time.
return MergeProfiles(std::move(profiles), std::move(serialized_profiles));
void PendingProfiles::SetCollectionEnabled(bool enabled) {
base::AutoLock scoped_lock(lock_);
collection_enabled_ = enabled;
if (!collection_enabled_) {
last_collection_disable_time_ = base::TimeTicks::Now();
} else {
last_collection_enable_time_ = base::TimeTicks::Now();
bool PendingProfiles::IsCollectionEnabledForProfile(
base::TimeTicks profile_start_time) const {
// Scenario 1: return false if collection is disabled.
if (!collection_enabled_)
return false;
// Scenario 2: return false if collection is disabled after the start of
// collection for this profile.
if (!last_collection_disable_time_.is_null() &&
last_collection_disable_time_ >= profile_start_time) {
return false;
// Scenario 3: return false if collection is disabled before the start of
// collection and re-enabled after the start. Note that this is different from
// scenario 1 where re-enabling never happens.
if (!last_collection_disable_time_.is_null() &&
!last_collection_enable_time_.is_null() &&
last_collection_enable_time_ >= profile_start_time) {
return false;
return true;
bool PendingProfiles::HasSpareCapacity() const {
return (unserialized_profiles_.size() + serialized_profiles_.size()) <
void PendingProfiles::MaybeCollectProfile(base::TimeTicks profile_start_time,
SampledProfile profile) {
base::AutoLock scoped_lock(lock_);
if (!IsCollectionEnabledForProfile(profile_start_time))
// Store the unserialized profile directly if there's room.
if (unserialized_profiles_.size() < kMaxPendingUnserializedProfiles) {
// This early return is strictly a performance optimization to avoid doing
// unnecessary serialization below. For correctness, since the
// serialization happens without holding the lock, it's necessary to check
// this condition again prior to actually collecting the serialized profile.
if (!HasSpareCapacity())
// There was no room to store the unserialized profile directly, but there was
// room to store it in serialized form. Serialize the profile without holding
// the lock, then try again to store it.
std::string serialized_profile;
void PendingProfiles::MaybeCollectSerializedProfile(
base::TimeTicks profile_start_time,
std::string serialized_profile) {
base::AutoLock scoped_lock(lock_);
if (IsCollectionEnabledForProfile(profile_start_time) && HasSpareCapacity())
void PendingProfiles::ResetToDefaultStateForTesting() {
base::AutoLock scoped_lock(lock_);
collection_enabled_ = true;
last_collection_disable_time_ = base::TimeTicks();
last_collection_enable_time_ = base::TimeTicks();
// |collection_enabled_| is initialized to true to collect any profiles that are
// generated prior to creation of the CallStackProfileMetricsProvider. The
// ultimate disposition of these pre-creation collected profiles will be
// determined by the initial recording state provided to
// CallStackProfileMetricsProvider.
PendingProfiles::PendingProfiles() : collection_enabled_(true) {}
} // namespace
// CallStackProfileMetricsProvider --------------------------------------------
const base::Feature CallStackProfileMetricsProvider::kEnableReporting = {
"SamplingProfilerReporting", base::FEATURE_DISABLED_BY_DEFAULT};
CallStackProfileMetricsProvider::CallStackProfileMetricsProvider() {}
CallStackProfileMetricsProvider::~CallStackProfileMetricsProvider() {}
// static
void CallStackProfileMetricsProvider::ReceiveProfile(
base::TimeTicks profile_start_time,
SampledProfile profile) {
// static
void CallStackProfileMetricsProvider::ReceiveSerializedProfile(
base::TimeTicks profile_start_time,
std::string serialized_profile) {
profile_start_time, std::move(serialized_profile));
void CallStackProfileMetricsProvider::OnRecordingEnabled() {
void CallStackProfileMetricsProvider::OnRecordingDisabled() {
void CallStackProfileMetricsProvider::ProvideCurrentSessionData(
ChromeUserMetricsExtension* uma_proto) {
std::vector<SampledProfile> profiles =
DCHECK(base::FeatureList::IsEnabled(kEnableReporting) || profiles.empty());
for (auto& profile : profiles)
*uma_proto->add_sampled_profile() = std::move(profile);
// static
void CallStackProfileMetricsProvider::ResetStaticStateForTesting() {
} // namespace metrics