question about cpusets vs sched_setaffinity()

From: Chris Friesen
Date: Thu Dec 10 2015 - 16:38:54 EST


Hi,

I've got a question about the interaction between cpusets and sched_setaffinity().

If I put a task into a cpuset and then call sched_setaffinity() on it, it will be affined to the intersection of the two sets of cpus. (Those specified on the set, and those specified in the syscall.)

However, if I then change the cpus in the cpuset the process affinity will simply be overwritten by the new cpuset affinity. It does not seem to take into account any restrictions from the original sched_setaffinity() call.

Wouldn't it make more sense to affine the process to the intersection between the new set of cpus from the cpuset, and the current process affinity? That way if I explicitly masked out certain CPUs in the original sched_setaffinity() call then they would remain masked out regardless of changes to the set of cpus assigned to the cpuset.

Thanks,
Chris

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