Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755555AbbETVAl (ORCPT ); Wed, 20 May 2015 17:00:41 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:38199 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754021AbbETVAe (ORCPT ); Wed, 20 May 2015 17:00:34 -0400 Date: Wed, 20 May 2015 14:00:26 -0700 From: "Paul E. McKenney" To: Afzal Mohammed Cc: Mike Galbraith , Sasha Levin , Frederic Weisbecker , Ingo Molnar , LKML , Chris Metcalf , "Rafael J . Wysocki" , Peter Zijlstra , Dave Jones , Thomas Gleixner , Oleg Nesterov , Ingo Molnar , Rik van Riel , Martin Schwidefsky Subject: Re: [PATCH 4/4] nohz: Set isolcpus when nohz_full is set Message-ID: <20150520210026.GC6776@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1430928266-24888-1-git-send-email-fweisbec@gmail.com> <1430928266-24888-5-git-send-email-fweisbec@gmail.com> <55579CE0.5060801@gmail.com> <1431840650.3222.78.camel@gmail.com> <20150520203809.GA2940@afzalpc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150520203809.GA2940@afzalpc> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15052021-0009-0000-0000-00000B03DF6A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1527 Lines: 38 On Thu, May 21, 2015 at 02:08:09AM +0530, Afzal Mohammed wrote: > Hi, > > On Sun, May 17, 2015 at 07:30:50AM +0200, Mike Galbraith wrote: > > > Yeah, tying nohz_full set to isolcpus set up an initial condition that > > you have to tear down with cpusets if you want those cpus returned to > > the general purpose pool. I had considered the kernel setting initial > > state to be an optimization, but have reconsidered. > > > Given that kernel initiated association to isolcpus, a user turning > > NO_HZ_FULL_ALL on had better not have much generic load to manage. If > > On a quad-core desktop system with NO_HZ_FULL_ALL, hackbench took 3x > time as compared to w/o this patch, except boot cpu every one else > jobless. Though NO_HZ_FULL_ALL (afaik) is not meant for generic load, > it was working fine, but not after this - it is now like a single core > system. I have to ask... What is your use case? What are you wanting NO_HZ_FULL to do for you? Thanx, Paul > Regards > Afzal > > > he/she does not have CPUSETS enabled, or should Rik's patch rendering > > isolcpus immutable be merged, he/she would quickly discover that the > > generic box has been transformed into an utterly inflexible specialist > > incapable of performing mundane tasks ever again. > -- 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/