// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40284755): Remove this and spanify to fix the errors.
#pragma allow_unsafe_buffers
#endif
#include "base/trace_event/cpufreq_monitor_android.h"
#include <fcntl.h>
#include "base/files/file_util.h"
#include "base/files/scoped_file.h"
#include "base/functional/bind.h"
#include "base/memory/scoped_refptr.h"
#include "base/no_destructor.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "base/strings/stringprintf.h"
#include "base/task/task_traits.h"
#include "base/task/thread_pool.h"
#include "base/trace_event/trace_event.h"
#include "base/types/fixed_array.h"
namespace base {
namespace trace_event {
namespace {
const size_t kNumBytesToReadForSampling = 32;
constexpr const char kTraceCategory[] = TRACE_DISABLED_BY_DEFAULT("power");
const char kEventTitle[] = "CPU Frequency";
} // namespace
CPUFreqMonitorDelegate::CPUFreqMonitorDelegate() {}
std::string CPUFreqMonitorDelegate::GetScalingCurFreqPathString(
unsigned int cpu_id) const {
return base::StringPrintf(
"/sys/devices/system/cpu/cpu%d/cpufreq/scaling_cur_freq", cpu_id);
}
bool CPUFreqMonitorDelegate::IsTraceCategoryEnabled() const {
bool enabled;
TRACE_EVENT_CATEGORY_GROUP_ENABLED(kTraceCategory, &enabled);
return enabled;
}
unsigned int CPUFreqMonitorDelegate::GetKernelMaxCPUs() const {
std::string str;
if (!base::ReadFileToString(
base::FilePath("/sys/devices/system/cpu/kernel_max"), &str)) {
// If we fail to read the kernel_max file, we just assume that CPU0 exists.
return 0;
}
unsigned int kernel_max_cpu = 0;
base::StringToUint(str, &kernel_max_cpu);
return kernel_max_cpu;
}
std::string CPUFreqMonitorDelegate::GetRelatedCPUsPathString(
unsigned int cpu_id) const {
return base::StringPrintf(
"/sys/devices/system/cpu/cpu%d/cpufreq/related_cpus", cpu_id);
}
void CPUFreqMonitorDelegate::GetCPUIds(std::vector<unsigned int>* ids) const {
ids->clear();
unsigned int kernel_max_cpu = GetKernelMaxCPUs();
// CPUs related to one that's already marked for monitoring get set to "false"
// so we don't needlessly monitor CPUs with redundant frequency information.
base::FixedArray<bool> cpus_to_monitor(kernel_max_cpu + 1, true);
// Rule out the related CPUs for each one so we only end up with the CPUs
// that are representative of the cluster.
for (unsigned int i = 0; i <= kernel_max_cpu; i++) {
if (!cpus_to_monitor[i])
continue;
std::string filename = GetRelatedCPUsPathString(i);
std::string line;
if (!base::ReadFileToString(base::FilePath(filename), &line))
continue;
// When reading the related_cpus file, we expected the format to be
// something like "0 1 2 3" for CPU0-3 if they're all in one cluster.
for (auto& str_piece :
base::SplitString(line, " ", base::WhitespaceHandling::TRIM_WHITESPACE,
base::SplitResult::SPLIT_WANT_NONEMPTY)) {
unsigned int cpu_id;
if (base::StringToUint(str_piece, &cpu_id)) {
if (cpu_id != i && cpu_id <= kernel_max_cpu)
cpus_to_monitor[cpu_id] = false;
}
}
ids->push_back(i);
}
// If none of the files were readable, we assume CPU0 exists and fall back to
// using that.
if (ids->size() == 0)
ids->push_back(0);
}
void CPUFreqMonitorDelegate::RecordFrequency(unsigned int cpu_id,
unsigned int freq) {
TRACE_COUNTER_ID1(kTraceCategory, kEventTitle, cpu_id, freq);
}
scoped_refptr<SingleThreadTaskRunner>
CPUFreqMonitorDelegate::CreateTaskRunner() {
return base::ThreadPool::CreateSingleThreadTaskRunner(
{base::MayBlock(), base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN,
base::TaskPriority::BEST_EFFORT},
base::SingleThreadTaskRunnerThreadMode::SHARED);
}
CPUFreqMonitor::CPUFreqMonitor()
: CPUFreqMonitor(std::make_unique<CPUFreqMonitorDelegate>()) {}
CPUFreqMonitor::CPUFreqMonitor(std::unique_ptr<CPUFreqMonitorDelegate> delegate)
: delegate_(std::move(delegate)) {}
CPUFreqMonitor::~CPUFreqMonitor() {
Stop();
}
// static
CPUFreqMonitor* CPUFreqMonitor::GetInstance() {
static base::NoDestructor<CPUFreqMonitor> instance;
return instance.get();
}
void CPUFreqMonitor::OnTraceLogEnabled() {
GetOrCreateTaskRunner()->PostTask(
FROM_HERE,
base::BindOnce(&CPUFreqMonitor::Start, weak_ptr_factory_.GetWeakPtr()));
}
void CPUFreqMonitor::OnTraceLogDisabled() {
Stop();
}
void CPUFreqMonitor::Start() {
// It's the responsibility of the caller to ensure that Start/Stop are
// synchronized. If Start/Stop are called asynchronously where this value
// may be incorrect, we have bigger problems.
if (is_enabled_.load(std::memory_order_relaxed) ||
!delegate_->IsTraceCategoryEnabled()) {
return;
}
std::vector<unsigned int> cpu_ids;
delegate_->GetCPUIds(&cpu_ids);
std::vector<std::pair<unsigned int, base::ScopedFD>> fds;
for (unsigned int id : cpu_ids) {
std::string fstr = delegate_->GetScalingCurFreqPathString(id);
int fd = open(fstr.c_str(), O_RDONLY);
if (fd == -1)
continue;
fds.emplace_back(std::make_pair(id, base::ScopedFD(fd)));
}
// We failed to read any scaling_cur_freq files, no point sampling nothing.
if (fds.size() == 0)
return;
is_enabled_.store(true, std::memory_order_release);
GetOrCreateTaskRunner()->PostTask(
FROM_HERE,
base::BindOnce(&CPUFreqMonitor::Sample, weak_ptr_factory_.GetWeakPtr(),
std::move(fds)));
}
void CPUFreqMonitor::Stop() {
is_enabled_.store(false, std::memory_order_release);
}
void CPUFreqMonitor::Sample(
std::vector<std::pair<unsigned int, base::ScopedFD>> fds) {
// For the same reason as above we use relaxed ordering, because if this value
// is in transition and we use acquire ordering then we'll never shut down our
// original Sample tasks until the next Stop, so it's still the responsibility
// of callers to sync Start/Stop.
if (!is_enabled_.load(std::memory_order_relaxed))
return;
for (auto& id_fd : fds) {
int fd = id_fd.second.get();
unsigned int freq = 0;
// If we have trouble reading data from the file for any reason we'll end up
// reporting the frequency as nothing.
lseek(fd, 0L, SEEK_SET);
char data[kNumBytesToReadForSampling];
ssize_t bytes_read = read(fd, data, kNumBytesToReadForSampling);
if (bytes_read > 0) {
if (static_cast<size_t>(bytes_read) < kNumBytesToReadForSampling)
data[static_cast<size_t>(bytes_read)] = '\0';
int ret = sscanf(data, "%d", &freq);
if (ret == 0 || ret == std::char_traits<char>::eof())
freq = 0;
}
delegate_->RecordFrequency(id_fd.first, freq);
}
GetOrCreateTaskRunner()->PostDelayedTask(
FROM_HERE,
base::BindOnce(&CPUFreqMonitor::Sample, weak_ptr_factory_.GetWeakPtr(),
std::move(fds)),
base::Milliseconds(kDefaultCPUFreqSampleIntervalMs));
}
bool CPUFreqMonitor::IsEnabledForTesting() {
return is_enabled_.load(std::memory_order_acquire);
}
const scoped_refptr<SingleThreadTaskRunner>&
CPUFreqMonitor::GetOrCreateTaskRunner() {
if (!task_runner_)
task_runner_ = delegate_->CreateTaskRunner();
return task_runner_;
}
} // namespace trace_event
} // namespace base
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