hal/android/AndroidHeterogeneousCpuInfo.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
   6
   7 #include "Hal.h"
   8 #include "HalLog.h"
   9 #include "HalTypes.h"
  10
  11 #include "mozilla/BitSet.h"
  12 #include "mozilla/CheckedInt.h"
  13 #include "prsystem.h"
  14 #include <fstream>
  15
  16 namespace mozilla::hal_impl {
  17
  18 mozilla::Maybe<HeterogeneousCpuInfo> CreateHeterogeneousCpuInfo() {
  19   CheckedInt<size_t> cpuCount = PR_GetNumberOfProcessors();
  20   if (!cpuCount.isValid()) {
  21     HAL_ERR("HeterogeneousCpuInfo: Failed to query processor count");
  22     return Nothing();
  23   }
  24
  25   if (cpuCount.value() > HeterogeneousCpuInfo::MAX_CPUS) {
  26     HAL_ERR("HeterogeneousCpuInfo: Too many cpus");
  27     return Nothing();
  28   }
  29
  30   std::vector<std::pair<int, int>> cpu_freqs;
  31   cpu_freqs.reserve(cpuCount.value());
  32   for (size_t i = 0; i < cpuCount.value(); i++) {
  33     std::stringstream freq_filename;
  34     // On all devices tested, even with isolated content processes we do have
  35     // permission to read this file. If, however, this function stops working
  36     // one day, then this may be a good place to start investigating.
  37     freq_filename << "/sys/devices/system/cpu/cpu" << i
  38                   << "/cpufreq/cpuinfo_max_freq";
  39     std::ifstream ifs(freq_filename.str());
  40     if (!ifs) {
  41       HAL_ERR("HeterogeneousCpuInfo: Failed to open file %s",
  42               freq_filename.str().c_str());
  43       return Nothing();
  44     }
  45     int freq;
  46     if (!(ifs >> freq)) {
  47       HAL_ERR("HeterogeneousCpuInfo: Failed to parse file %s",
  48               freq_filename.str().c_str());
  49       return Nothing();
  50     }
  51     cpu_freqs.push_back(std::make_pair(i, freq));
  52   }
  53
  54   std::sort(cpu_freqs.begin(), cpu_freqs.end(),
  55             [](auto lhs, auto rhs) { return lhs.second < rhs.second; });
  56
  57   HeterogeneousCpuInfo info;
  58   info.mTotalNumCpus = cpuCount.value();
  59
  60   int lowest_freq = cpu_freqs.front().second;
  61   int highest_freq = cpu_freqs.back().second;
  62   for (const auto& [cpu, freq] : cpu_freqs) {
  63     if (freq == highest_freq) {
  64       info.mBigCpus[cpu] = true;
  65     } else if (freq == lowest_freq) {
  66       info.mLittleCpus[cpu] = true;
  67     } else {
  68       info.mMediumCpus[cpu] = true;
  69     }
  70   }
  71
  72   HAL_LOG("HeterogeneousCpuInfo: little: %zu, med: %zu, big: %zu",
  73           info.mLittleCpus.Count(), info.mMediumCpus.Count(),
  74           info.mBigCpus.Count());
  75
  76   return Some(info);
  77 }
  78
  79 const Maybe<HeterogeneousCpuInfo>& GetHeterogeneousCpuInfo() {
  80   static const Maybe<HeterogeneousCpuInfo> cpuInfo =
  81       CreateHeterogeneousCpuInfo();
  82   return cpuInfo;
  83 }
  84
  85 }  // namespace mozilla::hal_impl