ProcessMetrics::GetCPUUsage() is Slow

base/process/process_metrics.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains routines for gathering resource statistics for processes
 // running on the system.
 
 #ifndef BASE_PROCESS_PROCESS_METRICS_H_
 #define BASE_PROCESS_PROCESS_METRICS_H_
 
@@ skipping 229 matching lines @@
 // limit, whichever is lower.
 BASE_EXPORT void SetFdLimit(unsigned int max_descriptors);
 #endif  // defined(OS_POSIX)
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
 // Parse the data found in /proc/<pid>/stat and return the sum of the
 // CPU-related ticks.  Returns -1 on parse error.
 // 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.
 // Returns 0 on failure.
 BASE_EXPORT int GetNumberOfThreads(ProcessHandle process);
 
 // /proc/self/exe refers to the current executable.
 BASE_EXPORT extern const char kProcSelfExe[];
 
 // Data from /proc/meminfo about system-wide memory consumption.
@@ skipping 123 matching lines @@
   SystemDiskInfo disk_info_;
 #endif
 #if defined(OS_CHROMEOS)
   SwapInfo swap_info_;
 #endif
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_METRICS_H_