profiler/native/perfd/cpu/cpu_usage_sampler.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef PERFD_CPU_CPU_USAGE_SAMPLER_H_
#define PERFD_CPU_CPU_USAGE_SAMPLER_H_

#include <cstdint>
#include <memory>
#include <mutex>
#include <unordered_set>

#include "proto/cpu.grpc.pb.h"
#include "utils/clock.h"
#include "utils/procfs_files.h"

namespace profiler {

class CpuCache;

class CpuUsageSampler {
 public:
  // Creates a CPU usage data collector that saves data to |cpu_cache|.
  CpuUsageSampler(Clock* clock, CpuCache* cpu_cache)
      : clock_(clock), cache_(*cpu_cache), usage_files_(new ProcfsFiles()) {}

  virtual ~CpuUsageSampler() = default;

  // Starts collecting usage data for process with ID of |pid|, if not already.
  profiler::proto::CpuStartResponse::Status AddProcess(int32_t pid);

  // Stops collecting usage data for process specified by ID |pid|. Does nothing
  // if |pid| is not being monitored.
  profiler::proto::CpuStopResponse::Status RemoveProcess(int32_t pid);

  // Samples CPU data of all processes that need monitoring. Saves the data to
  // |cache_|. Returns true if successfully sampling all processes.
  bool Sample();

  // Samples the CPU data of a process, including the system-wide usage as a
  // context for this process' usage percentage. Returns true on success.
  // TODO: Handle the case if there is no running process of |pid|.
  // Used by new pipeline's CPU usage sampler hence being public.
  virtual bool SampleAProcess(int32_t pid, profiler::proto::CpuUsageData* data);

 protected:
  // Resets where to look for (non-default) usage files.
  // This method is protected because it is supposed to be used for testing
  // only, by inheriting this class.
  void ResetUsageFiles(std::unique_ptr<ProcfsFiles> usage_files) {
    usage_files_ = std::move(usage_files);
  }

 private:
  // PIDs of app process that are being profiled.
  std::unordered_set<int32_t> pids_{};
  std::mutex pids_mutex_;
  // Clock that timestamps sample data.
  Clock* clock_;
  // Cache where collected data will be saved.
  CpuCache& cache_;
  // Files that are used to sample CPU usage. Configurable for testing.
  std::unique_ptr<const ProcfsFiles> usage_files_;
};

}  // namespace profiler

#endif  // PERFD_CPU_CPU_USAGE_SAMPLER_H_