Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753973AbbHXIAU (ORCPT ); Mon, 24 Aug 2015 04:00:20 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:33483 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752356AbbHXIAR (ORCPT ); Mon, 24 Aug 2015 04:00:17 -0400 Date: Mon, 24 Aug 2015 10:00:11 +0200 From: Ingo Molnar To: Mike Galbraith Cc: "Paul E. McKenney" , Frederic Weisbecker , Peter Zijlstra , LKML , Vatika Harlalka , Chris Metcalf , Thomas Gleixner , Preeti U Murthy , Christoph Lameter Subject: Re: [PATCH RESEND] sched/nohz: Affine unpinned timers to housekeepers Message-ID: <20150824080011.GA23649@gmail.com> References: <1439516774-4614-1-git-send-email-fweisbec@gmail.com> <20150823054032.GA28133@gmail.com> <20150823160101.GA11078@linux.vnet.ibm.com> <20150824064412.GA11581@gmail.com> <1440400997.3430.12.camel@gmail.com> <20150824074141.GA19209@gmail.com> <1440402888.3430.18.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1440402888.3430.18.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: 1421 Lines: 41 * Mike Galbraith wrote: > On Mon, 2015-08-24 at 09:41 +0200, Ingo Molnar wrote: > > * Mike Galbraith wrote: > > > > > On Mon, 2015-08-24 at 08:44 +0200, Ingo Molnar wrote: > > > > > > > the 'housekeeping CPU' is essentially the boot CPU. Yet we dedicate a full mask to > > > > it (housekeeping_mask - a variable mask to begin with) and recover the > > > > housekeeping CPU via: > > > > > > > > + return cpumask_any_and(housekeeping_mask, cpu_online_mask); > > > > > > There can be, and had better be if box is big, multiple housekeepers. > > > > Yes - but that does not seem to be possible via the code right now AFAICS, so > > at minimum it's incomplete. > > In master housekeepers are set up in tick_nohz_init(). Everybody who's not a > nohz_full CPU is a housekeeper. Ah, indeed, I missed the nohz_full= boot option: static int __init tick_nohz_full_setup(char *str) { alloc_bootmem_cpumask_var(&tick_nohz_full_mask); if (cpulist_parse(str, tick_nohz_full_mask) < 0) { Ok, first question is resolved - but the second one, behavior on boot CPU unplug still holds. Thanks, Ingo -- 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/