How to use sched_getaffinity and sched_setaffinity in Linux from C?

Question

I am trying to:

• Run 16 copies concurrently with processor pinning (2 copies per core)

• Run 8 copies concurrently with processor pinning (2 co

Answer 1

Don't use CPU_SETSIZE as cpusetsize parameter for sched_[set|get]affinity. The names are misleading but this is wrong. The macro CPU_SETSIZE is (quoting man 3 cpu_set) "a value one greater than the maximum CPU number that can be stored in cpu_set_t." You have to use

sched_setaffinity(0, sizeof(cpu_set_t), &my_set);

instead.