From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756937AbbIXOyn (ORCPT ); Thu, 24 Sep 2015 10:54:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38352 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752829AbbIXOyk (ORCPT ); Thu, 24 Sep 2015 10:54:40 -0400 Date: Thu, 24 Sep 2015 10:54:36 -0400 From: Luiz Capitulino To: Frederic Weisbecker 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: <20150924105436.1ebb93f9@redhat.com> In-Reply-To: <20150924144418.GB8569@lerouge> References: <1441915107-2000-1-git-send-email-lcapitulino@redhat.com> <1441915107-2000-4-git-send-email-lcapitulino@redhat.com> <20150924144418.GB8569@lerouge> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Sep 2015 16:44:18 +0200 Frederic Weisbecker wrote: > 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. Makes sense. > > Thanks. > > > #endif > > } > > } > > -- > > 2.1.0 > > >