Add CurrentProcessInfo::CreationTime() for Linux

base/process/process_metrics_linux.cc

 // 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.
 
 #include "base/process/process_metrics.h"
 
 #include <dirent.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/time.h>
@@ skipping 149 matching lines @@
 
 bool ProcessMetrics::GetWorkingSetKBytes(WorkingSetKBytes* ws_usage) const {
 #if defined(OS_CHROMEOS)
   if (GetWorkingSetKBytesTotmaps(ws_usage))
     return true;
 #endif
   return GetWorkingSetKBytesStatm(ws_usage);
 }
 
 double ProcessMetrics::GetCPUUsage() {
-  // This queries the /proc-specific scaling factor which is
-  // conceptually the system hertz.  To dump this value on another
-  // system, try
-  //   od -t dL /proc/self/auxv
-  // and look for the number after 17 in the output; mine is
-  //   0000040          17         100           3   134512692
-  // which means the answer is 100.
-  // It may be the case that this value is always 100.
-  static const int kHertz = sysconf(_SC_CLK_TCK);
-
   struct timeval now;
   int retval = gettimeofday(&now, NULL);
   if (retval)
     return 0;
   int64 time = TimeValToMicroseconds(now);
 
   if (last_time_ == 0) {
     // First call, just set the last values.
     last_time_ = time;
     last_cpu_ = GetProcessCPU(process_);
     return 0;
   }
 
   int64 time_delta = time - last_time_;
   DCHECK_NE(time_delta, 0);
   if (time_delta == 0)
     return 0;
 
   int cpu = GetProcessCPU(process_);
 
   // We have the number of jiffies in the time period.  Convert to percentage.
   // Note this means we will go *over* 100 in the case where multiple threads
   // are together adding to more than one CPU's worth.
-  int percentage = 100 * (cpu - last_cpu_) /
-      (kHertz * TimeDelta::FromMicroseconds(time_delta).InSecondsF());
+  TimeDelta cpu_time = internal::ClockTicksToTimeDelta(cpu);
+  TimeDelta last_cpu_time = internal::ClockTicksToTimeDelta(last_cpu_);
+  int percentage = 100 * (cpu_time - last_cpu_time).InSecondsF() /
+      TimeDelta::FromMicroseconds(time_delta).InSecondsF();
 
   last_time_ = time;
   last_cpu_ = cpu;
 
   return percentage;
 }
 
 // To have /proc/self/io file you must enable CONFIG_TASK_IO_ACCOUNTING
 // in your kernel configuration.
 bool ProcessMetrics::GetIOCounters(IoCounters* io_counters) const {
@@ skipping 300 matching lines @@
 }
 
 const char kProcSelfExe[] = "/proc/self/exe";
 
 int GetNumberOfThreads(ProcessHandle process) {
   return internal::ReadProcStatsAndGetFieldAsInt(process,
                                                  internal::VM_NUMTHREADS);
 }
 
 }  // namespace base