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

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Message-ID: <ZIewlkGJJJUXPFL0@google.com>
Date:   Mon, 12 Jun 2023 16:56:06 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     jiangshanlai@...il.com, torvalds@...ux-foundation.org,
        peterz@...radead.org, linux-kernel@...r.kernel.org,
        kernel-team@...a.com, joshdon@...gle.com, brho@...gle.com,
        nhuck@...gle.com, agk@...hat.com, snitzer@...nel.org,
        void@...ifault.com, treapking@...omium.org
Subject: Re: [PATCHSET v1 wq/for-6.5] workqueue: Improve unbound workqueue
 execution locality

Hi,

On Thu, May 18, 2023 at 02:16:45PM -1000, Tejun Heo wrote:
> In terms of patches, 0021-0024 are probably the interesting ones.
> 
> Brian Norris, Nathan Huckleberry and others experiencing wq perf problems
> -------------------------------------------------------------------------
> 
> Can you please test this patchset and see whether the performance problems
> are resolved? After the patchset, unbound workqueues default to
> soft-affining on cache boundaries, which should hopefully resolve the issues
> that you guys have been seeing on recent kernels on heterogeneous CPUs.
> 
> If you want to try different settings, please read:
> 
>  https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git/tree/Documentation/core-api/workqueue.rst?h=affinity-scopes-v1&id=e8f3505e69a526cc5fe40a4da5d443b7f9231016#n350

Thanks for the CC; my colleague tried out your patches (ported to 5.15
with some minor difficulty), and aside from some crashes (already noted
by others, although we didn't pull the proposed v2 fixes), he didn't
notice a significant change in performance on our particular test system
and WiFi-throughput workload. I don't think we expected a lot though,
per the discussion at:

https://lore.kernel.org/all/ZFvpJb9Dh0FCkLQA@google.com/

Brian