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

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Message-ID: <0000014117e497c1-6b04f29f-c4f8-4178-b69b-aa2233ba343b-000000@email.amazonses.com>
Date:	Fri, 13 Sep 2013 15:15:59 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Frederic Weisbecker <fweisbec@...il.com>,
	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>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC] Restrict kernel spawning of threads to a specified set of
 cpus.

On Fri, 13 Sep 2013, Peter Zijlstra wrote:

> No, creating a parent for them closes the race. It should also makes it
> lots easier to find the kids by using ppid.

Ok if all spawning is done from kthreadd then that works.

> > A kernel parameter would allow a clean bootup with threads
> > starting out on the specific processors we want them to.
>
> Blergh, no. A kernel should boot, a kernel should allow you to configure
> things, a kernel should not be limited to boot time settings.

The kernel is not limited but can decide where to place threads. The
threads spawned for general user space services are limited to a set of
cpus unless there is an explict override. The intend is to keep as much
processing as possible away from the notick processors.




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