Re: [PATCH v3 1/3] sched/fair: Move checking for nohz cpus after time check

From: Peter Zijlstra
Date: Thu Jan 08 2026 - 08:48:20 EST


On Wed, Jan 07, 2026 at 12:21:23PM +0530, Shrikanth Hegde wrote:
> NOHZ idle load balancer is kicked off only after time check. So move
> the atomic read after the time check to access it only when needed.
>
> When there are no idle CPUs(100% busy), even if the flag gets set to
> NOHZ_STATS_KICK | NOHZ_NEXT_KICK, find_new_ilb will fail and
> there will be no NOHZ idle balance. The current behaviour is retained.
>
> Note: This patch doesn't solve any cacheline overheads. No improvement
> in performance apart from saving a few cycles of atomic_read.

Note that atomic_read() == READ_ONCE() is just a regular load, but sure.