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SubjectRe: [PATCHSET v1 wq/for-6.5] workqueue: Improve unbound workqueue execution locality
Hello,

On Mon, Jun 12, 2023 at 04:56:06PM -0700, Brian Norris wrote:
> 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

Yeah, there were a few subtle bugs that v2 fixes.

> 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/

That's disappointing. I was actually expecting that the default behavior
would restrain migrations across L3 boundaries strong enough to make a
meaningful difference. Can you enable WQ_SYSFS and test the following
configs?

1. affinity_scope = cache, affinity_strict = 1

2. affinity_scope = cpu, affinity_strict = 0

3. affinity_scope = cpu, affinity_strict = 1

#3 basically turns it into a percpu workqueue, so it should perform more or
less the same as a percpu workqueue without affecting everyone else.

Any chance you can post the toplogy details on the affected setup? How are
the caches and cores laid out?

Thanks.

--
tejun

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