From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753384Ab3J3DPu (ORCPT ); Tue, 29 Oct 2013 23:15:50 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:55120 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753121Ab3J3DPt (ORCPT ); Tue, 29 Oct 2013 23:15:49 -0400 Subject: [PATCH V2 1/2] sched: Fix asymmetric scheduling for POWER7 To: peterz@infradead.org, mikey@neuling.org, svaidy@linux.vnet.ibm.com, mingo@kernel.org From: Preeti U Murthy Cc: vincent.guittot@linaro.org, bitbucket@online.de, benh@kernel.crashing.org, linux-kernel@vger.kernel.org, anton@samba.org, linuxppc-dev@lists.ozlabs.org, Morten.Rasmussen@arm.com, pjt@google.com Date: Wed, 30 Oct 2013 08:42:42 +0530 Message-ID: <20131030031242.23426.13019.stgit@preeti.in.ibm.com> In-Reply-To: <20131030031145.23426.22930.stgit@preeti.in.ibm.com> References: <20131030031145.23426.22930.stgit@preeti.in.ibm.com> User-Agent: StGit/0.16-38-g167d MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13103003-0320-0000-0000-0000018F41A6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vaidyanathan Srinivasan Asymmetric scheduling within a core is a scheduler loadbalancing feature that is triggered when SD_ASYM_PACKING flag is set. The goal for the load balancer is to move tasks to lower order idle SMT threads within a core on a POWER7 system. In nohz_kick_needed(), we intend to check if our sched domain (core) is completely busy or we have idle cpu. The following check for SD_ASYM_PACKING: (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu) already covers the case of checking if the domain has an idle cpu, because cpumask_first_and() will not yield any set bits if this domain has no idle cpu. Hence, nr_busy check against group weight can be removed. Reported-by: Michael Neuling Signed-off-by: Vaidyanathan Srinivasan Signed-off-by: Preeti U Murthy Tested-by: Michael Neuling --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 813dd61..e9c9549 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6781,7 +6781,7 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu) 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 + if (sd->flags & SD_ASYM_PACKING && (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)) goto need_kick_unlock;