How can I measure CPU time of a specific set of threads?

Question

I run C++ program in Linux.

There are several threads pool (for computation, for io, for ... such things).

The system call clock() gives me a way to measure the CPU time spent by all the CPU cores for the process.

However, I want to measure the CPU time spent only by the threads in the computation threads pool.

How can I achieve it?

Thanks :D

Fendley

This is not ideal, but i think the easiest solution is to log some message with timestamps of start and stop of each thread and get you timings by postprocessing those logs. – Clothes

Answer 1

To get CPU clock ID of every thread you can use: pthread_getcpuclockid and using this CPU clock ID you can retrieve the current thread CPU time using: clock_gettime.

Following is the sample code to demonstrate the same:

struct timespec currTime;
clockid_t threadClockId;

//! Get thread clock Id
pthread_getcpuclockid(pthread_self(), &threadClockId);
//! Using thread clock Id get the clock time
clock_gettime(threadClockId, &currTime);

Fugacious

It seems you can also call clock_gettime(CLOCK_THREAD_CPUTIME_ID, &currTime) according to manual so you don't need pthread dependency. – Oppenheimer