Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932376AbbHXB3A (ORCPT ); Sun, 23 Aug 2015 21:29:00 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:34488 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932356AbbHXB25 (ORCPT ); Sun, 23 Aug 2015 21:28:57 -0400 Date: Mon, 24 Aug 2015 03:28:51 +0200 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: Ingo Molnar , 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: <20150824012849.GB20044@lerouge> References: <1439516774-4614-1-git-send-email-fweisbec@gmail.com> <20150823054032.GA28133@gmail.com> <20150823160101.GA11078@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150823160101.GA11078@linux.vnet.ibm.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: 1072 Lines: 27 On Sun, Aug 23, 2015 at 09:01:01AM -0700, Paul E. McKenney wrote: > The boot CPU is excluded from tick_nohz_full_mask in tick_nohz_init(), > which is called from tick_init() which is called from start_kernel() > shortly after rcu_init(): > > cpu = smp_processor_id(); > > if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { > pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu); > cpumask_clear_cpu(cpu, tick_nohz_full_mask); > } > > This happens after the call to tick_nohz_init_all() that does the > cpumask_setall() that you called out above. > > Or is a recent patch that I missed changing this? Exactly, this happens right after tick_nohz_full_mask is filled and makes sure that at least the boot CPU runs as a housekeeper. We also make sure that it can't become offline later. Thanks. -- 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/