From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755272AbcCWM0B (ORCPT ); Wed, 23 Mar 2016 08:26:01 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:35595 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755237AbcCWMZw (ORCPT ); Wed, 23 Mar 2016 08:25:52 -0400 X-IBM-Helo: d23dlp03.au.ibm.com X-IBM-MailFrom: srikar@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: Srikar Dronamraju To: Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, srikar@linux.vnet.ibm.com, Rik van Riel Subject: [PATCH 2/3] Reset nr_balance_failed after active balancing Date: Wed, 23 Mar 2016 17:54:44 +0530 Message-Id: <1458735884-30105-1-git-send-email-srikar@linux.vnet.ibm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1458732880-28382-1-git-send-email-srikar@linux.vnet.ibm.com> References: <1458732880-28382-1-git-send-email-srikar@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16032312-0017-0000-0000-000003F03B92 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To force a task migration during active balancing, nr_balance_failed is set to cache_nice_tries + 1. However nr_balance_failed is not reset. As a side effect, the next regular load balance under the same sd, a cache hot task might be migrated, just because nr_balance_failed count is high. Resetting the nr_balance_failed after a successful active balance, ensures that a hot task is not unreasonably migrated. This can be verified by looking at number of hot task migrations reported by /proc/schedstat. Signed-off-by: Srikar Dronamraju --- kernel/sched/fair.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 9abfb16..fae05f4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7294,10 +7294,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, &busiest->active_balance_work); } - /* - * We've kicked active balancing, reset the failure - * counter. - */ + /* We've kicked active balancing, force task migration. */ sd->nr_balance_failed = sd->cache_nice_tries+1; } } else @@ -7532,10 +7529,13 @@ static int active_load_balance_cpu_stop(void *data) schedstat_inc(sd, alb_count); p = detach_one_task(&env); - if (p) + if (p) { schedstat_inc(sd, alb_pushed); - else + /* Active balancing done, reset the failure counter. */ + sd->nr_balance_failed = 0; + } else { schedstat_inc(sd, alb_failed); + } } rcu_read_unlock(); out_unlock: -- 1.8.3.1