From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A1FAC433EF for ; Tue, 21 Sep 2021 10:03:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63A0E60F9E for ; Tue, 21 Sep 2021 10:03:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231540AbhIUKE5 (ORCPT ); Tue, 21 Sep 2021 06:04:57 -0400 Received: from outbound-smtp19.blacknight.com ([46.22.139.246]:38825 "EHLO outbound-smtp19.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230160AbhIUKEy (ORCPT ); Tue, 21 Sep 2021 06:04:54 -0400 Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp19.blacknight.com (Postfix) with ESMTPS id A21F21C59C9 for ; Tue, 21 Sep 2021 11:03:25 +0100 (IST) Received: (qmail 18526 invoked from network); 21 Sep 2021 10:03:25 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 21 Sep 2021 10:03:25 -0000 Date: Tue, 21 Sep 2021 11:03:23 +0100 From: Mel Gorman To: Peter Zijlstra Cc: Vincent Guittot , Ingo Molnar , Valentin Schneider , Aubrey Li , Barry Song , Srikar Dronamraju , LKML Subject: Re: [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt_wakeup Message-ID: <20210921100323.GL3959@techsingularity.net> References: <20210920142614.4891-1-mgorman@techsingularity.net> <20210920142614.4891-2-mgorman@techsingularity.net> <20210921075309.GK3959@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 21, 2021 at 10:21:19AM +0200, Peter Zijlstra wrote: > On Tue, Sep 21, 2021 at 08:53:09AM +0100, Mel Gorman wrote: > > On Tue, Sep 21, 2021 at 09:21:16AM +0200, Vincent Guittot wrote: > > > On Mon, 20 Sept 2021 at 16:26, Mel Gorman wrote: > > > > > > > > The rq for curr is read during the function preamble, remove the > > > > redundant lookup. > > > > > > > > Signed-off-by: Mel Gorman > > > > --- > > > > 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 ff69f245b939..038edfaaae9e 100644 > > > > --- a/kernel/sched/fair.c > > > > +++ b/kernel/sched/fair.c > > > > @@ -7190,7 +7190,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ > > > > if (cse_is_idle != pse_is_idle) > > > > return; > > > > > > > > - update_curr(cfs_rq_of(se)); > > > > + update_curr(cfs_rq); > > > > > > se can have been modified by find_matching_se(&se, &pse) > > > > > > > I still expected the cfs_rq to be the same, particularly given that the > > context is about preempting the current task on a runqueue. Is that > > wrong? > > Yes. There's a cfs_rq for every se. What we do in find_matching_se() is > walk up the hiarachy until both are in the same cfs_rq, otherwse we > cannot compare them. > > Fundamentally this means the effective cfs_rq also changes. Ok, thanks. I'll read into this more but the patch is dead. -- Mel Gorman SUSE Labs