linux-kernel - Re: [patch,v2] bdi: add a user-tunable cpu

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Date:	Thu, 6 Dec 2012 19:19:34 +0100
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Jeff Moyer <jmoyer@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Zach Brown <zab@...hat.com>,
	Peter Zijlstra <pzijlstr@...hat.com>, Ingo <mingo@...hat.com>
Subject: Re: [patch,v2] bdi: add a user-tunable cpu_list for the bdi flusher
 threads

On 2012-12-06 19:01, Tejun Heo wrote:
> As for the original patch, I think it's a bit too much to expose to
> userland.  It's probably a good idea to bind the flusher to the local
> node but do we really need to expose an interface to let userland
> control the affinity directly?  Do we actually have a use case at
> hand?

We need to expose it. Once the binding is set from the kernel side on a
kernel thread, it can't be modified.

Binding either for performance reasons or for ensuring that we
explicitly don't run in some places is a very useful feature.

-- 
Jens Axboe

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