Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755584Ab3ILSfK (ORCPT ); Thu, 12 Sep 2013 14:35:10 -0400 Received: from mail-wg0-f52.google.com ([74.125.82.52]:61482 "EHLO mail-wg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753000Ab3ILSfI (ORCPT ); Thu, 12 Sep 2013 14:35:08 -0400 Date: Thu, 12 Sep 2013 20:35:05 +0200 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: Christoph Lameter , Andrew Morton , Gilad Ben-Yossef , Thomas Gleixner , Mike Frysinger , linux-kernel@vger.kernel.org Subject: Re: [RFC] Restrict kernel spawning of threads to a specified set of cpus. Message-ID: <20130912183503.GB25386@somewhere> References: <00000140efbcb701-c26320b3-f434-4538-bc80-8e92fed6f303-000000@email.amazonses.com> <20130911220228.GB15367@somewhere> <000001411282afa6-fe9c0543-0447-492b-991e-dc8214884b88-000000@email.amazonses.com> <20130912141625.GA23357@somewhere> <00000141128d759a-44dcacb6-8f48-4f9b-8381-d14003bd6da1-000000@email.amazonses.com> <20130912143137.GA23839@somewhere> <0000014112a921ae-51d171bf-e8d4-4569-bd20-94dabda2d5ba-000000@email.amazonses.com> <20130912151102.GB23839@somewhere> <20130912153922.GP3966@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130912153922.GP3966@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1655 Lines: 36 On Thu, Sep 12, 2013 at 08:39:22AM -0700, Paul E. McKenney wrote: > On Thu, Sep 12, 2013 at 05:11:04PM +0200, Frederic Weisbecker wrote: > > On Thu, Sep 12, 2013 at 02:52:56PM +0000, Christoph Lameter wrote: > > > 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. > > > > Ok but really that's just two lines of bash. I really wish we don't complicate > > core kernel code for that. > > OK, I will bite... How do you handle the case where you have collected > all the kthreads, one of the kthreads spawns another kthread, then you > set affinity on the collected kthreads, which does not include the newly > spawned one? Just offline the CPUs you want to isolate, affine your kthreads and re-online the CPUs. If you're lucky enough to have 1024 CPUs, a winter night should be enough ;-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/