double ProcessMetrics::GetCPUUsage()
{
FILETIME now;
FILETIME creation_time;
FILETIME exit_time;
FILETIME kernel_time;
FILETIME user_time;
GetSystemTimeAsFileTime(&now);
if(!GetProcessTimes(process_, &creation_time, &exit_time,
&kernel_time, &user_time))
{
// We don't assert here because in some cases (such as in the Task Manager)
// we may call this function on a process that has just exited but we have
// not yet received the notification.
return 0;
}
int64 system_time = (FileTimeToUTC(kernel_time) + FileTimeToUTC(user_time)) /
processor_count_;
int64 time = FileTimeToUTC(now);
if((last_system_time_ == 0) || (last_time_ == 0))
{
// First call, just set the last values.
last_system_time_ = system_time;
last_time_ = time;
return 0;
}
int64 system_time_delta = system_time - last_system_time_;
int64 time_delta = time - last_time_;
DCHECK(time_delta != 0);
if(time_delta == 0)
{
return 0;
}
// We add time_delta / 2 so the result is rounded.
int cpu = static_cast<int>((system_time_delta * 100 + time_delta / 2) /
time_delta);
last_system_time_ = system_time;
last_time_ = time;
return cpu;
}
double ProcessMetrics::GetCPUUsage() {
FILETIME creation_time;
FILETIME exit_time;
FILETIME kernel_time;
FILETIME user_time;
if (!GetProcessTimes(process_, &creation_time, &exit_time,
&kernel_time, &user_time)) {
// We don't assert here because in some cases (such as in the Task Manager)
// we may call this function on a process that has just exited but we have
// not yet received the notification.
return 0;
}
int64 system_time = (FileTimeToUTC(kernel_time) + FileTimeToUTC(user_time)) /
processor_count_;
TimeTicks time = TimeTicks::Now();
if (last_system_time_ == 0) {
// First call, just set the last values.
last_system_time_ = system_time;
last_cpu_time_ = time;
return 0;
}
int64 system_time_delta = system_time - last_system_time_;
// FILETIME is in 100-nanosecond units, so this needs microseconds times 10.
int64 time_delta = (time - last_cpu_time_).InMicroseconds() * 10;
DCHECK_NE(0U, time_delta);
if (time_delta == 0)
return 0;
// We add time_delta / 2 so the result is rounded.
int cpu = static_cast<int>((system_time_delta * 100 + time_delta / 2) /
time_delta);
last_system_time_ = system_time;
last_cpu_time_ = time;
return cpu;
}
