From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753244AbbIXOoW (ORCPT ); Thu, 24 Sep 2015 10:44:22 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:34531 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751400AbbIXOoV (ORCPT ); Thu, 24 Sep 2015 10:44:21 -0400 Date: Thu, 24 Sep 2015 16:44:18 +0200 From: Frederic Weisbecker To: Luiz Capitulino Cc: linux-kernel@vger.kernel.org, cmetcalf@ezchip.com Subject: Re: [PATCH 3/3] sched: add_nr_running(): drop tick_nohz_full_cpu() check Message-ID: <20150924144418.GB8569@lerouge> References: <1441915107-2000-1-git-send-email-lcapitulino@redhat.com> <1441915107-2000-4-git-send-email-lcapitulino@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1441915107-2000-4-git-send-email-lcapitulino@redhat.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 On Thu, Sep 10, 2015 at 03:58:27PM -0400, Luiz Capitulino wrote: > tick_nohz_full_kick_cpu() performs the same check. > > Signed-off-by: Luiz Capitulino > --- > kernel/sched/sched.h | 20 +++++++++----------- > 1 file changed, 9 insertions(+), 11 deletions(-) > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 68cda11..102eb18 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1323,17 +1323,15 @@ static inline void add_nr_running(struct rq *rq, unsigned count) > #endif > > #ifdef CONFIG_NO_HZ_FULL > - if (tick_nohz_full_cpu(rq->cpu)) { > - /* > - * Tick is needed if more than one task runs on a CPU. > - * Send the target an IPI to kick it out of nohz mode. > - * > - * We assume that IPI implies full memory barrier and the > - * new value of rq->nr_running is visible on reception > - * from the target. > - */ > - tick_nohz_full_kick_cpu(rq->cpu); > - } > + /* > + * Tick is needed if more than one task runs on a CPU. > + * Send the target an IPI to kick it out of nohz mode. > + * > + * We assume that IPI implies full memory barrier and the > + * new value of rq->nr_running is visible on reception > + * from the target. > + */ > + tick_nohz_full_kick_cpu(rq->cpu); Nope, we want to keep this because tick_nohz_full_cpu() does a static key check. Most users don't care about nohz_full and I really want to keep nohz full off case overhead to the bare minimum. Thanks. > #endif > } > } > -- > 2.1.0 >