1 files changed, 85 insertions, 0 deletions
diff --git a/hal/android/AndroidHeterogeneousCpuInfo.cpp b/hal/android/AndroidHeterogeneousCpuInfo.cpp
new file mode 100644
index 0000000000..e51ebce260
--- /dev/null
+++ b/hal/android/AndroidHeterogeneousCpuInfo.cpp
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "Hal.h"
+#include "HalLog.h"
+#include "HalTypes.h"
+
+#include "mozilla/BitSet.h"
+#include "mozilla/CheckedInt.h"
+#include "prsystem.h"
+#include <fstream>
+
+namespace mozilla::hal_impl {
+
+mozilla::Maybe<HeterogeneousCpuInfo> CreateHeterogeneousCpuInfo() {
+  CheckedInt<size_t> cpuCount = PR_GetNumberOfProcessors();
+  if (!cpuCount.isValid()) {
+    HAL_ERR("HeterogeneousCpuInfo: Failed to query processor count");
+    return Nothing();
+  }
+
+  if (cpuCount.value() > HeterogeneousCpuInfo::MAX_CPUS) {
+    HAL_ERR("HeterogeneousCpuInfo: Too many cpus");
+    return Nothing();
+  }
+
+  std::vector<std::pair<int, int>> cpu_freqs;
+  cpu_freqs.reserve(cpuCount.value());
+  for (size_t i = 0; i < cpuCount.value(); i++) {
+    std::stringstream freq_filename;
+    // On all devices tested, even with isolated content processes we do have
+    // permission to read this file. If, however, this function stops working
+    // one day, then this may be a good place to start investigating.
+    freq_filename << "/sys/devices/system/cpu/cpu" << i
+                  << "/cpufreq/cpuinfo_max_freq";
+    std::ifstream ifs(freq_filename.str());
+    if (!ifs) {
+      HAL_ERR("HeterogeneousCpuInfo: Failed to open file %s",
+              freq_filename.str().c_str());
+      return Nothing();
+    }
+    int freq;
+    if (!(ifs >> freq)) {
+      HAL_ERR("HeterogeneousCpuInfo: Failed to parse file %s",
+              freq_filename.str().c_str());
+      return Nothing();
+    }
+    cpu_freqs.push_back(std::make_pair(i, freq));
+  }
+
+  std::sort(cpu_freqs.begin(), cpu_freqs.end(),
+            [](auto lhs, auto rhs) { return lhs.second < rhs.second; });
+
+  HeterogeneousCpuInfo info;
+  info.mTotalNumCpus = cpuCount.value();
+
+  int lowest_freq = cpu_freqs.front().second;
+  int highest_freq = cpu_freqs.back().second;
+  for (const auto& [cpu, freq] : cpu_freqs) {
+    if (freq == highest_freq) {
+      info.mBigCpus[cpu] = true;
+    } else if (freq == lowest_freq) {
+      info.mLittleCpus[cpu] = true;
+    } else {
+      info.mMediumCpus[cpu] = true;
+    }
+  }
+
+  HAL_LOG("HeterogeneousCpuInfo: little: %zu, med: %zu, big: %zu",
+          info.mLittleCpus.Count(), info.mMediumCpus.Count(),
+          info.mBigCpus.Count());
+
+  return Some(info);
+}
+
+const Maybe<HeterogeneousCpuInfo>& GetHeterogeneousCpuInfo() {
+  static const Maybe<HeterogeneousCpuInfo> cpuInfo =
+      CreateHeterogeneousCpuInfo();
+  return cpuInfo;
+}
+
+}  // namespace mozilla::hal_impl