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

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Message-ID: <20170718193615.GB3365493@devbig577.frc2.facebook.com>
Date:   Tue, 18 Jul 2017 15:36:15 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Alexei Potashnik <alexei@...estorage.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: doc change for ST behavior on NUMA systems

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