linux-kernel - Re: [RFC] Restrict kernel spawning of threads to a specified set of cpus.

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Message-ID: <0000014112a921ae-51d171bf-e8d4-4569-bd20-94dabda2d5ba-000000@email.amazonses.com>
Date:	Thu, 12 Sep 2013 14:52:56 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Frysinger <vapier@...too.org>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC] Restrict kernel spawning of threads to a specified set of
 cpus.

On Thu, 12 Sep 2013, Frederic Weisbecker wrote:

> > > Ok but you can change the affinity of a kthread from userspace, as
> > > long as you define a cpu set that is among that kthread's cpus allowed.
> >
> > Ok but at that point kthread has already spawned a lot of kernel threads.
> >
> > The same is true for init and kmod.
> >
>
> Ok but then we just need to set the affinity of all these kthreads.
> A simple lookup on /proc/[0-9]+/ should do the trick.

Yea but the kernel option makes it easy. No extras needed. Kernel brings
it up user space cleanly configured and ready to go.

This also allows us to cleanup kernel uses of cpumasks in such a way that
proper thread placement for various other uses (reclaim f.e. kswpad) is
possible.


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