Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754596AbbETUiU (ORCPT ); Wed, 20 May 2015 16:38:20 -0400 Received: from mail-pd0-f174.google.com ([209.85.192.174]:33019 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753178AbbETUiR (ORCPT ); Wed, 20 May 2015 16:38:17 -0400 Date: Thu, 21 May 2015 02:08:09 +0530 From: Afzal Mohammed To: Mike Galbraith Cc: Sasha Levin , Frederic Weisbecker , Ingo Molnar , LKML , Chris Metcalf , "Rafael J . Wysocki" , Peter Zijlstra , Dave Jones , Thomas Gleixner , Oleg Nesterov , "Paul E . McKenney" , Ingo Molnar , Rik van Riel , Martin Schwidefsky Subject: Re: [PATCH 4/4] nohz: Set isolcpus when nohz_full is set Message-ID: <20150520203809.GA2940@afzalpc> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1431840650.3222.78.camel@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1301 Lines: 30 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. 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/