ProcessMetrics::GetCPUUsage() is Slow

base/process/process_metrics.h

Index: base/process/process_metrics.h
diff --git a/base/process/process_metrics.h b/base/process/process_metrics.h
index 5916b94148cb2e6e9a6782096bcca49fd7b8f41a..6bd6aad5da75a4468486964d5787389c8939f16b 100644
--- a/base/process/process_metrics.h
+++ b/base/process/process_metrics.h
@@ -247,6 +247,14 @@ BASE_EXPORT void SetFdLimit(unsigned int max_descriptors);
 // Exposed for testing.
 BASE_EXPORT int ParseProcStatCPU(const std::string& input);
 
+// Extract the sum of the CPU-related ticks from the given |input| which
+// contains the stats found in /proc/<pid>/stat. Returns -1 on error.
+//
+// Use this version instead of the above for faster results.
+//
+// Exposed for testing.
+BASE_EXPORT int GetCpuFromProcStats(const std::string& input);

[danakj, 2015/02/03 18:51:09]

why are you adding a new method with the same return values as the old one, and
replacing the one callsite, instead of just changing the old method?

[afakhry, 2015/02/03 20:23:54]

I wanted to keep the old one for reference, but you're right, no need to do
this, Hence, removed.

+
 // Get the number of threads of |process| as available in /proc/<pid>/stat.
 // This should be used with care as no synchronization with running threads is
 // done. This is mostly useful to guarantee being single-threaded.