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// Copyright 2014 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/macros.h"
#include "base/memory/singleton.h"
#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
#include "base/trace_event/trace_event_synthetic_delay.h"
namespace {
const int kMaxSyntheticDelays = 32;
} // namespace
namespace base {
namespace trace_event {
TraceEventSyntheticDelayClock::TraceEventSyntheticDelayClock() {}
TraceEventSyntheticDelayClock::~TraceEventSyntheticDelayClock() {}
class TraceEventSyntheticDelayRegistry : public TraceEventSyntheticDelayClock {
public:
static TraceEventSyntheticDelayRegistry* GetInstance();
TraceEventSyntheticDelay* GetOrCreateDelay(const char* name);
void ResetAllDelays();
// TraceEventSyntheticDelayClock implementation.
TimeTicks Now() override;
private:
TraceEventSyntheticDelayRegistry();
friend struct DefaultSingletonTraits<TraceEventSyntheticDelayRegistry>;
Lock lock_;
TraceEventSyntheticDelay delays_[kMaxSyntheticDelays];
TraceEventSyntheticDelay dummy_delay_;
subtle::Atomic32 delay_count_;
DISALLOW_COPY_AND_ASSIGN(TraceEventSyntheticDelayRegistry);
};
TraceEventSyntheticDelay::TraceEventSyntheticDelay()
: mode_(STATIC), begin_count_(0), trigger_count_(0), clock_(NULL) {}
TraceEventSyntheticDelay::~TraceEventSyntheticDelay() {}
TraceEventSyntheticDelay* TraceEventSyntheticDelay::Lookup(
const std::string& name) {
return TraceEventSyntheticDelayRegistry::GetInstance()->GetOrCreateDelay(
name.c_str());
}
void TraceEventSyntheticDelay::Initialize(
const std::string& name,
TraceEventSyntheticDelayClock* clock) {
name_ = name;
clock_ = clock;
}
void TraceEventSyntheticDelay::SetTargetDuration(TimeDelta target_duration) {
AutoLock lock(lock_);
target_duration_ = target_duration;
trigger_count_ = 0;
begin_count_ = 0;
}
void TraceEventSyntheticDelay::SetMode(Mode mode) {
AutoLock lock(lock_);
mode_ = mode;
}
void TraceEventSyntheticDelay::SetClock(TraceEventSyntheticDelayClock* clock) {
AutoLock lock(lock_);
clock_ = clock;
}
void TraceEventSyntheticDelay::Begin() {
// Note that we check for a non-zero target duration without locking to keep
// things quick for the common case when delays are disabled. Since the delay
// calculation is done with a lock held, it will always be correct. The only
// downside of this is that we may fail to apply some delays when the target
// duration changes.
ANNOTATE_BENIGN_RACE(&target_duration_, "Synthetic delay duration");
if (!target_duration_.ToInternalValue())
return;
TimeTicks start_time = clock_->Now();
{
AutoLock lock(lock_);
if (++begin_count_ != 1)
return;
end_time_ = CalculateEndTimeLocked(start_time);
}
}
void TraceEventSyntheticDelay::BeginParallel(TimeTicks* out_end_time) {
// See note in Begin().
ANNOTATE_BENIGN_RACE(&target_duration_, "Synthetic delay duration");
if (!target_duration_.ToInternalValue()) {
*out_end_time = TimeTicks();
return;
}
TimeTicks start_time = clock_->Now();
{
AutoLock lock(lock_);
*out_end_time = CalculateEndTimeLocked(start_time);
}
}
void TraceEventSyntheticDelay::End() {
// See note in Begin().
ANNOTATE_BENIGN_RACE(&target_duration_, "Synthetic delay duration");
if (!target_duration_.ToInternalValue())
return;
TimeTicks end_time;
{
AutoLock lock(lock_);
if (!begin_count_ || --begin_count_ != 0)
return;
end_time = end_time_;
}
if (!end_time.is_null())
ApplyDelay(end_time);
}
void TraceEventSyntheticDelay::EndParallel(TimeTicks end_time) {
if (!end_time.is_null())
ApplyDelay(end_time);
}
TimeTicks TraceEventSyntheticDelay::CalculateEndTimeLocked(
TimeTicks start_time) {
if (mode_ == ONE_SHOT && trigger_count_++)
return TimeTicks();
else if (mode_ == ALTERNATING && trigger_count_++ % 2)
return TimeTicks();
return start_time + target_duration_;
}
void TraceEventSyntheticDelay::ApplyDelay(TimeTicks end_time) {
TRACE_EVENT0("synthetic_delay", name_.c_str());
while (clock_->Now() < end_time) {
// Busy loop.
}
}
TraceEventSyntheticDelayRegistry*
TraceEventSyntheticDelayRegistry::GetInstance() {
return Singleton<
TraceEventSyntheticDelayRegistry,
LeakySingletonTraits<TraceEventSyntheticDelayRegistry> >::get();
}
TraceEventSyntheticDelayRegistry::TraceEventSyntheticDelayRegistry()
: delay_count_(0) {}
TraceEventSyntheticDelay* TraceEventSyntheticDelayRegistry::GetOrCreateDelay(
const char* name) {
// Try to find an existing delay first without locking to make the common case
// fast.
int delay_count = subtle::Acquire_Load(&delay_count_);
for (int i = 0; i < delay_count; ++i) {
if (!strcmp(name, delays_[i].name_.c_str()))
return &delays_[i];
}
AutoLock lock(lock_);
delay_count = subtle::Acquire_Load(&delay_count_);
for (int i = 0; i < delay_count; ++i) {
if (!strcmp(name, delays_[i].name_.c_str()))
return &delays_[i];
}
DCHECK(delay_count < kMaxSyntheticDelays)
<< "must increase kMaxSyntheticDelays";
if (delay_count >= kMaxSyntheticDelays)
return &dummy_delay_;
delays_[delay_count].Initialize(std::string(name), this);
subtle::Release_Store(&delay_count_, delay_count + 1);
return &delays_[delay_count];
}
TimeTicks TraceEventSyntheticDelayRegistry::Now() {
return TimeTicks::Now();
}
void TraceEventSyntheticDelayRegistry::ResetAllDelays() {
AutoLock lock(lock_);
int delay_count = subtle::Acquire_Load(&delay_count_);
for (int i = 0; i < delay_count; ++i) {
delays_[i].SetTargetDuration(TimeDelta());
delays_[i].SetClock(this);
}
}
void ResetTraceEventSyntheticDelays() {
TraceEventSyntheticDelayRegistry::GetInstance()->ResetAllDelays();
}
} // namespace trace_event
} // namespace base
namespace trace_event_internal {
ScopedSyntheticDelay::ScopedSyntheticDelay(const char* name,
base::subtle::AtomicWord* impl_ptr)
: delay_impl_(GetOrCreateDelay(name, impl_ptr)) {
delay_impl_->BeginParallel(&end_time_);
}
ScopedSyntheticDelay::~ScopedSyntheticDelay() {
delay_impl_->EndParallel(end_time_);
}
base::trace_event::TraceEventSyntheticDelay* GetOrCreateDelay(
const char* name,
base::subtle::AtomicWord* impl_ptr) {
base::trace_event::TraceEventSyntheticDelay* delay_impl =
reinterpret_cast<base::trace_event::TraceEventSyntheticDelay*>(
base::subtle::Acquire_Load(impl_ptr));
if (!delay_impl) {
delay_impl =
base::trace_event::TraceEventSyntheticDelayRegistry::GetInstance()
->GetOrCreateDelay(name);
base::subtle::Release_Store(
impl_ptr, reinterpret_cast<base::subtle::AtomicWord>(delay_impl));
}
return delay_impl;
}
} // namespace trace_event_internal
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