linux-kernel - Re: [PATCH v2] fs/nfsd/nfs4callback: Remove deprecated create_singlethread

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Message-ID: <1472655685.5795.10.camel@redhat.com>
Date:   Wed, 31 Aug 2016 11:01:25 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Bhaktipriya Shridhar <bhaktipriya96@...il.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fs/nfsd/nfs4callback: Remove deprecated
 create_singlethread_workqueue

On Wed, 2016-08-31 at 10:39 -0400, Tejun Heo wrote:
> Hello, Jeff.
> 
> On Tue, Aug 30, 2016 at 05:07:23PM -0400, Jeff Layton wrote:
> > 
> > Hah! I have almost exactly the same patch in my tree. I've only not
> > sent it because I haven't had the chance to test it well.
> > 
> > The only difference in mine is that it passes in WQ_UNBOUND. ISTM
> > that
> > we don't really need a bound workqueue here since we only use this
> > to
> > kick off callbacks to the client. I doubt we'd get much out of
> > strictly
> > maintaining cache locality here, and we're better off just sending
> > it
> > the callback as quickly as possible.
> 
> We recently broke strong locality guarantee for users which don't use
> queue_work_on(), so the default locality is now only for optimization
> instead of correctness anyway.  Unless there are actual benefits to
> using WQ_UNBOUND, I think in general it's better to stick with as
> little attributes as possible so that we have more maneuvering room
> down the line.  But, yeah, if this can impact performance in subtle
> ways, it could be best to just do an identity conversion at least for
> now.
> 
> Thanks.
> 

Ahh ok, thanks...that's good to know. If you think we don't need
WQ_UNBOUND then this is fine with me.

Reviewed-by: Jeff Layton <jlayton@...hat.com>