Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932743AbbHXHXZ (ORCPT ); Mon, 24 Aug 2015 03:23:25 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:35303 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932323AbbHXHXV (ORCPT ); Mon, 24 Aug 2015 03:23:21 -0400 Message-ID: <1440400997.3430.12.camel@gmail.com> Subject: Re: [PATCH RESEND] sched/nohz: Affine unpinned timers to housekeepers From: Mike Galbraith To: Ingo Molnar Cc: "Paul E. McKenney" , Frederic Weisbecker , Peter Zijlstra , LKML , Vatika Harlalka , Chris Metcalf , Thomas Gleixner , Preeti U Murthy , Christoph Lameter Date: Mon, 24 Aug 2015 09:23:17 +0200 In-Reply-To: <20150824064412.GA11581@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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 776 Lines: 20 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. Imagine a NO_HZ_FULL_ALL kernel on an SGI beast from hell. Offloading 8191 CPUs onto poor little CPU0 probably wouldn't work out well :) -Mike -- 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/