From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752695AbbC0L2c (ORCPT ); Fri, 27 Mar 2015 07:28:32 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:55989 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752226AbbC0L2b (ORCPT ); Fri, 27 Mar 2015 07:28:31 -0400 Date: Fri, 27 Mar 2015 16:58:23 +0530 From: Srikar Dronamraju To: Wanpeng Li Cc: Ingo Molnar , Peter Zijlstra , Jason Low , Preeti U Murthy , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched/fair: fix update the nohz.next_balance even if we haven't done any load balance Message-ID: <20150327112823.GC6895@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <1427442750-8112-1-git-send-email-wanpeng.li@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1427442750-8112-1-git-send-email-wanpeng.li@linux.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15032711-0021-0000-0000-000004687F58 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Wanpeng Li [2015-03-27 15:52:30]: > As Srikar pointed out (https://lkml.org/lkml/2015/3/27/26): > > | With the current code when the ilb cpus are not free: > | - We would be updating the nohz.next_balance even through we havent done > | any load balance. > | - We might iterate thro the nohz.idle_cpus_mask()s to find balance_cpus. > > This patch fix it by adding need_resched check with the idle check, and > keep the need_resched check in for loop to catch ilb get busy. > > Suggested-by: Srikar Dronamraju > Reviewed-by: Jason Low > Signed-off-by: Wanpeng Li Looks good to me. Reviewed-by: Srikar Dronamraju > --- > 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 0576ce0..788e42f 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7638,7 +7638,7 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) > struct rq *rq; > int balance_cpu; > > - if (idle != CPU_IDLE || > + if (idle != CPU_IDLE || need_resched() || > !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) > goto end; > > -- > 1.9.1 > -- Thanks and Regards Srikar Dronamraju