Re: [RFC workqueue/driver-core PATCH 1/5] workqueue: Provide queue_work_near to queue work near a given NUMA node

Tejun Heo
2018-10-02T17:41:22Z

Hello,

On Mon, Oct 01, 2018 at 02:54:39PM -0700, Alexander Duyck wrote:
> >It might be better to leave queue_work_on() to be used for per-cpu
> >workqueues and introduce queue_work_near() as you suggseted. I just
> >don't want it to duplicate the node selection code in it. Would that
> >work?
>
> So if I understand what you are saying correctly we default to
> round-robin on a given node has no CPUs attached to it. I could
> probably work with that if that is the default behavior instead of
> adding much of the complexity I already have.

Yeah, it's all in wq_select_unbound_cpu(). Right now, if the
requested cpu isn't in wq_unbound_cpumask, it falls back to dumb
round-robin. We can probably do better there and find the nearest
node considering topology.

> The question I have then is what should I do about workqueues that
> aren't WQ_UNBOUND if they attempt to use queue_work_near? In that

Hmm... yeah, let's just use queue_work_on() for now. We can sort it
out later and users could already do that anyway.

Thanks.

--
tejun