Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754274Ab3JVOg1 (ORCPT ); Tue, 22 Oct 2013 10:36:27 -0400 Received: from e23smtp04.au.ibm.com ([202.81.31.146]:47889 "EHLO e23smtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753807Ab3JVOgY (ORCPT ); Tue, 22 Oct 2013 10:36:24 -0400 Date: Tue, 22 Oct 2013 20:05:59 +0530 From: Kamalesh Babulal To: Vaidyanathan Srinivasan Cc: Peter Zijlstra , Mike Galbraith , Paul Turner , Ingo Molnar , Michael Neuling , Benjamin Herrenschmidt , linux-kernel@vger.kernel.org, Anton Blanchard , Preeti U Murthy , linuxppc-dev@lists.ozlabs.org, vincent.guittot@linaro.org, suresh.b.siddha@intel.com Subject: Re: [PATCH 1/3] sched: Fix nohz_kick_needed to consider the nr_busy of the parent domain's group Message-ID: <20131022143559.GA3197@linux.vnet.ibm.com> Reply-To: Kamalesh Babulal References: <20131021114002.13291.31478.stgit@drishya> <20131021114442.13291.99344.stgit@drishya> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20131021114442.13291.99344.stgit@drishya> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13102214-9264-0000-0000-000004C74207 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1789 Lines: 50 * Vaidyanathan Srinivasan [2013-10-21 17:14:42]: > for_each_domain(cpu, sd) { > - struct sched_group *sg = sd->groups; > - struct sched_group_power *sgp = sg->sgp; > - int nr_busy = atomic_read(&sgp->nr_busy_cpus); > - > - if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) > - goto need_kick_unlock; > + struct sched_domain *sd_parent = sd->parent; > + struct sched_group *sg; > + struct sched_group_power *sgp; > + int nr_busy; > + > + if (sd_parent) { > + sg = sd_parent->groups; > + sgp = sg->sgp; > + nr_busy = atomic_read(&sgp->nr_busy_cpus); > + > + if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) > + goto need_kick_unlock; > + } > > if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight > && (cpumask_first_and(nohz.idle_cpus_mask, CC'ing Suresh Siddha and Vincent Guittot Please correct me, If my understanding of idle balancing is wrong. With proposed approach will not idle load balancer kick in, even if there are busy cpus across groups or if there are 2 busy cpus which are spread across sockets. Consider 2 socket machine with 4 processors each (MC and NUMA domains). If the machine is partial loaded such that cpus 0,4,5,6,7 are busy, then too nohz balancing is triggered because with this approach (NUMA)->groups->sgp->nr_busy_cpus is taken in account for nohz kick, while iterating over MC domain. Isn't idle load balancer not suppose kick in, even in the case of two busy cpu's in a dual-core single socket system. Thanks, Kamalesh. -- 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/