Add an 'Idle Wake Ups' metric to the Linux task manager, implement backend.

base/process/process_metrics_linux.cc

Index: base/process/process_metrics_linux.cc
diff --git a/base/process/process_metrics_linux.cc b/base/process/process_metrics_linux.cc
index be166e33e322959bb7d10111e0746dbe5680c27f..9467ae8a54a9312b90ead46a0d9928842c173143 100644
--- a/base/process/process_metrics_linux.cc
+++ b/base/process/process_metrics_linux.cc
@@ -76,6 +76,38 @@ size_t ReadProcStatusAndGetFieldAsSizeT(pid_t pid, const std::string& field) {
   return 0;
 }
 
+// Read /proc/<pid>/sched and look for |field|. On succes, return true and
+// write the value for |field| into |result|.
+// Only works for fields in the form of "field    :     uint_value"
+bool ReadProcSchedAndGetFieldAsUint64(pid_t pid,
+                                      const std::string& field,
+                                      uint64* result) {
+  std::string sched_data;
+  {
+    // Synchronously reading files in /proc is safe.

[Nico, 2014/09/07 00:10:57]

"safe" isn't why we have this, it's about speed. I'd say "/proc is in memory, so
reading from it doesn't need to hit the disk." instead.

[Lei Zhang, 2014/09/09 06:13:14]

Filed all over. It's copy+pasted from elsewhere in this file. Maybe I wrote it
in the first place? *shrug*.

+    ThreadRestrictions::ScopedAllowIO allow_io;
+    FilePath sched_file = internal::GetProcPidDir(pid).Append("sched");
+    if (!ReadFileToString(sched_file, &sched_data))
+      return false;
+  }
+
+  std::vector<std::pair<std::string, std::string> > pairs;
+  SplitStringIntoKeyValuePairs(sched_data, ':', '\n', &pairs);
+  for (size_t i = 0; i < pairs.size(); ++i) {
+    std::string key, value_str;
+    TrimWhitespaceASCII(pairs[i].first, TRIM_ALL, &key);
+    TrimWhitespaceASCII(pairs[i].second, TRIM_ALL, &value_str);

[Nico, 2014/09/07 00:10:57]

This looks pretty similar to line 72 of
https://codereview.chromium.org/549753002/diff/40001/base/process/process_met...
– maybe there should be a helper that does the Trimming on first and second

[Lei Zhang, 2014/09/09 06:13:14]

Done.

+    if (key == field) {
+      uint64 value;
+      if (!StringToUint64(value_str, &value))
+        return false;
+      *result = value;
+      return true;
+    }
+  }
+  return false;
+}
+
 // Get the total CPU of a single process.  Return value is number of jiffies
 // on success or -1 on error.
 int GetProcessCPU(pid_t pid) {
@@ -234,6 +266,7 @@ bool ProcessMetrics::GetIOCounters(IoCounters* io_counters) const {
 ProcessMetrics::ProcessMetrics(ProcessHandle process)
     : process_(process),
       last_system_time_(0),
+      last_absolute_idle_wakeups_(0),
       last_cpu_(0) {
   processor_count_ = SysInfo::NumberOfProcessors();
 }
@@ -839,4 +872,11 @@ void GetSwapInfo(SwapInfo* swap_info) {
 }
 #endif  // defined(OS_CHROMEOS)
 
+int ProcessMetrics::GetIdleWakeupsPerSecond() {
+  uint64 wake_ups;
+  const char kWakeupStat[] = "se.statistics.nr_wakeups";
+  return ReadProcSchedAndGetFieldAsUint64(process_, kWakeupStat, &wake_ups) ?
+      CalculateIdleWakeupsPerSecond(wake_ups) : 0;
+}
+
 }  // namespace base