Re: [PATCH RFC 0/5] workqueue: add WQ_AFFN_CACHE_SHARD affinity scope

[Breno Leitao]

On Tue, Mar 17, 2026 at 09:58:54AM -0400, Chuck Lever wrote:
> On 3/17/26 7:32 AM, Breno Leitao wrote:
> >> - How was the default shard size of 8 picked? There's a tradeoff
> >> between the number of kworkers created and locality. Can you also
> >> report the number of kworkers for each configuration? And is there
> >> data on different shard sizes? It'd be useful to see how the numbers
> >> change across e.g. 4, 8, 16, 32.
> >
> > The choice of 8 as the default shard size was somewhat arbitrary – it was
> > selected primarily to generate initial data points.
>
> Perhaps instead of basing the sharding on a particular number of CPUs
> per shard, why not cap the total number of shards? IIUC that is the main
> concern about ballooning the number of kworker threads.

That's a great suggestion. I'll send a v2 that implements this approach,
where the parameter specifies the number of shards rather than the number
of CPUs per shard.

Thanks for the feedback,
--breno