Red Hat Summit Red Hat SummitSupportConsoleDevelopersStart a trialContact

6.2. Using the sched_setaffinity() System Call to Set Processor Affinity

In addition to the taskset command, processor affinity can also be set using the sched_setaffinity() system call.
The following code excerpt retrieves the CPU affinity information for a specified PID. If the PID passed to it is 0, it will return the affinity information for the current process: 
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>

int main(int argc, char **argv)
{
  int i, online=0;
  ulong ncores = sysconf(_SC_NPROCESSORS_CONF);
  cpu_set_t *setp = CPU_ALLOC(ncores);
  ulong setsz = CPU_ALLOC_SIZE(ncores);

  CPU_ZERO_S(setsz, setp);

  if (sched_getaffinity(0, setsz, setp) == -1) {
    perror("sched_getaffinity(2) failed");
    exit(errno);
  }

  for (i=0; i < CPU_COUNT_S(setsz, setp); i++) {
    if (CPU_ISSET_S(i, setsz, setp))
      online++;
  }
	
  printf("%d cores configured, %d cpus allowed in affinity mask\n", ncores, online);
  CPU_FREE(setp);
}
Copy to Clipboard Toggle word wrap

Note

For more information, or for further reading, the following man page is related to the information given in this section:
  • sched_setaffinity(2)
Back to top
Red Hat logoGithubredditYoutubeTwitter

Learn

Try, buy, & sell

Communities

About Red Hat Documentation

We help Red Hat users innovate and achieve their goals with our products and services with content they can trust. Explore our recent updates.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. For more details, see the Red Hat Blog.

About Red Hat

We deliver hardened solutions that make it easier for enterprises to work across platforms and environments, from the core datacenter to the network edge.

Theme

© 2025 Red Hat