text: /*
   * Copyright (C) 2019 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.
   */
  
  #include <fcntl.h>
  #include <getopt.h>
  #include <inttypes.h>
  #include <stdint.h>
  #include <sys/stat.h>
  #include <sys/types.h>
  #include <time.h>
  #include <unistd.h>
  
  #include <string>
  
  #include "perfetto/base/logging.h"
  #include "perfetto/base/time.h"
  #include "perfetto/ext/base/scoped_file.h"
  
  // Periodically prints an un-normalized cpu usage ratio (full use of a single
  // core = 1.0) of a target process. Based on /proc/pid/stat utime (userspace) &
  // stime (kernel space).
  
  namespace perfetto {
  namespace {
  
  uint64_t TimespecToMs(struct timespec ts) {
    PERFETTO_CHECK(ts.tv_sec >= 0 && ts.tv_nsec >= 0);
    return static_cast<uint64_t>(ts.tv_sec) * 1000 +
           static_cast<uint64_t>(ts.tv_nsec) / 1000 / 1000;
  }
  
  uint64_t ReadWallTimeMs(clockid_t clk) {
    struct timespec ts = {};
    PERFETTO_CHECK(clock_gettime(clk, &ts) == 0);
    return TimespecToMs(ts);
  }
  
  void ReadUtimeStime(const base::ScopedFile& stat_fd,
                      unsigned long* utime_out,
                      unsigned long* stime_out) {
    char buf[1024] = {};
    lseek(stat_fd.get(), 0, SEEK_SET);
    PERFETTO_CHECK(read(stat_fd.get(), buf, sizeof(buf)) > 0);
    buf[sizeof(buf) - 1] = '\0';
  
    PERFETTO_CHECK(
        sscanf(buf, "%*d %*s %*c %*d %*d %*d %*d %*d %*u %*u %*u %*u %*u %lu %lu",
               utime_out, stime_out) == 2);
  }
  
  int CpuUtilizationMain(int argc, char** argv) {
    unsigned sleep_duration_us = 10 * 1000 * 1000;  // 10s
    int sleep_intervals = 6;
    int target_pid = -1;
  
    static struct option long_options[] = {
        {"pid", required_argument, nullptr, 'p'},
        {"sleep-duration-us", required_argument, nullptr, 't'},
        {"sleep-intervals", required_argument, nullptr, 'n'},
        {nullptr, 0, nullptr, 0}};
    int option_index;
    int c;
    while ((c = getopt_long(argc, argv, "", long_options, &option_index)) != -1) {
      switch (c) {
        case 'p':
          target_pid = atoi(optarg);
          break;
        case 't':
          sleep_duration_us = static_cast<unsigned>(atoi(optarg));
          break;
        case 'n':
          sleep_intervals = atoi(optarg);
          break;
        default:
          break;
      }
    }
  
    if (target_pid < 1) {
      PERFETTO_ELOG(
          "Usage: %s --pid=target_pid [--sleep-duration-us=N] "
          "[--sleep-intervals=N]",
          argv[0]);
      return 1;
    }
  
    // Resolution of utime/stime from procfs, at least 10 ms.
    long ticks = sysconf(_SC_CLK_TCK);
    PERFETTO_CHECK(ticks >= 100);
    unsigned long ticks_per_s = static_cast<unsigned long>(ticks);
  
    // Resolution of wallclock time, at least 1 ms. Should be O(ns) in practice.
    auto clk = CLOCK_MONOTONIC_RAW;
    struct timespec ts = {};
    PERFETTO_CHECK(clock_getres(clk, &ts) == 0);
    PERFETTO_CHECK(ts.tv_sec == 0 && ts.tv_nsec <= 1 * 1000 * 1000);
  
    PERFETTO_LOG("--- setup: ---");
    PERFETTO_LOG("target pid: %d", target_pid);
    PERFETTO_LOG("intervals: %d x %uus", sleep_intervals, sleep_duration_us);
    PERFETTO_LOG("utime/stime ticks per sec: %ld", ticks_per_s);
    PERFETTO_LOG("wall clock resolution (ns): %ld", ts.tv_nsec);
    PERFETTO_LOG("--- timings: ---");
  
    base::ScopedFile fd = base::OpenFile(
        std::string("/proc/") + std::to_string(target_pid) + std::string("/stat"),
        O_RDONLY);
    PERFETTO_CHECK(fd);
  
    // Read the base times.
    unsigned long first_utime = 0;
    unsigned long first_stime = 0;
    ReadUtimeStime(fd, &first_utime, &first_stime);
    uint64_t first_walltime_ms = ReadWallTimeMs(clk);
  
    uint64_t last_walltime_ms = first_walltime_ms;
    unsigned long last_utime = first_utime;
    unsigned long last_stime = first_stime;
  
    // Report the utilization for each fixed duration chunk.
    for (int i = 0; i < sleep_intervals; i++) {
      base::SleepMicroseconds(sleep_duration_us);
  
      unsigned long utime = 0;
      unsigned long stime = 0;
      ReadUtimeStime(fd, &utime, &stime);
      uint64_t walltime_ms = ReadWallTimeMs(clk);
  
      uint64_t wall_diff_ms = walltime_ms - last_walltime_ms;
      PERFETTO_LOG("wall_ms    : [%" PRIu64 "] - [%" PRIu64 "] = [%" PRIu64 "]",
                   walltime_ms, last_walltime_ms, wall_diff_ms);
  
      unsigned long utime_diff = utime - last_utime;
      unsigned long stime_diff = stime - last_stime;
      PERFETTO_LOG("utime_ticks: [%lu] - [%lu] = [%lu]", utime, last_utime,
                   utime_diff);
      PERFETTO_LOG("stime_ticks: [%lu] - [%lu] = [%lu]", stime, last_stime,
                   stime_diff);
  
      // Calculate the utilization, resolution of inputs will be no worse than
      // 10ms due to the above assert. At the default 10s wall time, we therefore
      // get a resolution of at least 0.1%.
      double utime_diff_ms = static_cast<double>(utime_diff * 1000 / ticks_per_s);
      double stime_diff_ms = static_cast<double>(stime_diff * 1000 / ticks_per_s);
  
      double utime_ratio = utime_diff_ms / static_cast<double>(wall_diff_ms);
      double stime_ratio = stime_diff_ms / static_cast<double>(wall_diff_ms);
  
      PERFETTO_LOG("utime ratio   : %f", utime_ratio);
      PERFETTO_LOG("stime ratio   : %f", stime_ratio);
      PERFETTO_LOG("combined ratio: %f\n", utime_ratio + stime_ratio);
  
      last_walltime_ms = walltime_ms;
      last_utime = utime;
      last_stime = stime;
    }
  
    PERFETTO_LOG("--- timings over the whole period: ---");
    unsigned long utime_diff = last_utime - first_utime;
    unsigned long stime_diff = last_stime - first_stime;
    uint64_t wall_diff_ms = last_walltime_ms - first_walltime_ms;
    double utime_diff_ms = static_cast<double>(utime_diff * 1000 / ticks_per_s);
    double stime_diff_ms = static_cast<double>(stime_diff * 1000 / ticks_per_s);
    double utime_ratio = utime_diff_ms / static_cast<double>(wall_diff_ms);
    double stime_ratio = stime_diff_ms / static_cast<double>(wall_diff_ms);
    PERFETTO_LOG("utime ratio   : %f", utime_ratio);
    PERFETTO_LOG("stime ratio   : %f", stime_ratio);
    PERFETTO_LOG("combined ratio: %f\n", utime_ratio + stime_ratio);
  
    return 0;
  }
  
  }  // namespace
  }  // namespace perfetto
  
  int main(int argc, char** argv) {
    return perfetto::CpuUtilizationMain(argc, argv);
  }
  