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

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Date:   Tue, 8 Aug 2023 08:28:53 +0530
From:   K Prateek Nayak <kprateek.nayak@....com>
To:     Tejun Heo <tj@...nel.org>, 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
Subject: Re: [PATCHSET v1 wq/for-6.5] workqueue: Improve unbound workqueue
 execution locality

Hello Tejun,

On 8/8/2023 6:52 AM, Tejun Heo wrote:
> 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.

Sure. I'll retest with for-6.6 branch. Will post the results here once the
tests are done. I'll repeat the same - test with the defaults and the ones
that show any difference in results, I'll rerun them with various affinity
scopes.

Let me know if you have any suggestions.

--
Thanks and Regards,
Prateek