Re: [PATCH 1/2] cgroup/cpuset: Keep current cpus list if cpus affinity was explicitly set

[Michal Koutný]

On Thu, Jul 28, 2022 at 10:59:01AM -0400, Waiman Long <longman@xxxxxxxxxx> wrote:
> Cgroup v1 doesn't have this problem.

v1 analogy would be:

	echo 2-3 >$dst/cpuset.cpus
	# job runs in $dst
	# one task T in $dst sets affinity just to one cpu
	# I rethink my config, I want to allow $dst more space
	echo 2-5 >$dst/cpuset.cpus

Most tasks in $dst happily utilize the new cpus but it breaks affinity
for T -- this must have been broken since ever.

(Or I'd argue that per-thread affinities are just recommendations, if I
have a task for nohz CPU, I should enforce its placement with cpuset
from the beginning.)

Michal