linux-kernel - Re: [PATCHSET v1 wq/for-6.5] workqueue: Improve unbound workqueue execution locality

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Date:   Mon, 7 Aug 2023 15:22:12 -1000
From:   Tejun Heo <tj@...nel.org>
To:     jiangshanlai@...il.com
Cc:     torvalds@...ux-foundation.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, kernel-team@...a.com,
        joshdon@...gle.com, brho@...gle.com, briannorris@...omium.org,
        nhuck@...gle.com, agk@...hat.com, snitzer@...nel.org,
        void@...ifault.com, kprateek.nayak@....com
Subject: Re: [PATCHSET v1 wq/for-6.5] workqueue: Improve unbound workqueue
 execution locality

Hello,

On Thu, May 18, 2023 at 02:16:45PM -1000, Tejun Heo wrote:
> Unbound workqueues used to spray work items inside each NUMA node, which
> isn't great on CPUs w/ multiple L3 caches. This patchset implements
> mechanisms to improve and configure execution locality.

The patchset shows minor perf improvements for some but more importantly
gives users more control over worker placement which helps working around
some of the recently reported performance regressions. Prateek reported
concerning regressions with tbench but I couldn't reproduce it and can't see
how tbench would be affected at all given the benchmark doesn't involve
workqueue operations in any noticeable way.

Assuming that the tbench difference was a testing artifact, I'm applying the
patchset to wq/for-6.6 so that it can receive wider testing. Prateek, I'd
really appreciate if you could repeat the test and see whether the
difference persists.

Thanks.

-- 
tejun