Re: [PATCH] workqueue: doc change for ST behavior on NUMA systems

From: Tejun Heo
Date: Tue Jul 18 2017 - 15:36:26 EST


On Tue, Jul 18, 2017 at 12:18:29PM -0700, Christoph Hellwig wrote:
> On Tue, Jul 18, 2017 at 11:12:53AM -0700, Alexei Potashnik wrote:
> > NUMA rework of workqueue made the combination of max_active of 1 and
> > WQ_UNBOUND insufficient to guarantee ST behavior system wide.
> >
> > alloc_ordered_queue should now be used instead.
>
> Eww. And how many existing users might be broken by that?

Good point. create_singlethread_workqueue() maps to
alloc_ordered_workqueue(), so they're all good. Only the ones which
got converted to the new interface incorrectly would be broken. I
probably should make WQ_UNBOUND / 1 behave as ordered. I'll think
more about it.

Thanks!

--
tejun