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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 16D70C4338F for ; Mon, 23 Aug 2021 10:09:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED7DB61246 for ; Mon, 23 Aug 2021 10:09:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236170AbhHWKKa (ORCPT ); Mon, 23 Aug 2021 06:10:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235921AbhHWKK2 (ORCPT ); Mon, 23 Aug 2021 06:10:28 -0400 Received: from mail-lf1-x12f.google.com (mail-lf1-x12f.google.com [IPv6:2a00:1450:4864:20::12f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37ABAC061757 for ; Mon, 23 Aug 2021 03:09:45 -0700 (PDT) Received: by mail-lf1-x12f.google.com with SMTP id p38so36916421lfa.0 for ; Mon, 23 Aug 2021 03:09:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=05AJ+F6GkT8AKoB6zrVwfafs6BSYl8oX/Agcqv8i+MM=; b=xruKDw0o9Cc8GwxChKcJa0h4NpB0c+dUfM768lUIRH/VJqqAX5OTCciPqLXAlLUcpe y4T4Myh0FVZqLXSyFeoAJWb/qoIxJDukw/1ylKwIvxWvsEDL31OGNyblpS6l3sThV/F0 bzOLZ+pm/Q2LMeJVxWR1mN/3FB+gUHzpIO/4zKBHzX9AodzpKojmBdNu0F7NYgbjqDoU K45VISRoriUHQOyc0OLmmyMm1bPsODImVCpziKEXm77A45RT33Kv2D9BbsHGIwJA/fDS uODRbqS+oTUhUpGpMiU6FA/gqbIjWJFDYUe5qnpD7SGRF0Yhn0I390G4g4LROOM/qRWl 6aXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=05AJ+F6GkT8AKoB6zrVwfafs6BSYl8oX/Agcqv8i+MM=; b=rZl2JAR54oM8umXR0K+y7sC3efZXulTsYmNonRygQ6S3gDDqQl+pj7W2PcdJQN464u CT8q2C1oYjx4th1CYkUsazQ3qLjlRVhn29yI4zJweYaDC9FU+wReMnRzb1KMKWly1I0t +kVsRSZJsOZzZpkM8kUkd9DGvaINeMHpE8NOtZpv6PoENOAuu9RivoIBPl17NQ/Ei6/X l8b/Y7OxjKfEBru/DOpGmbUGHmiQbFkTPr8utsCyrPk+0daWr1eapBONESSUwA4+oAcR KI4SEhKmfhoFyBK2vRLfmnklzkfWgbXdWOEJTK/2e46d0zJ+1hSxV97BClCHfxKD4T0x g2wg== X-Gm-Message-State: AOAM530sNdd2q3c22CYi+qrKBOLOtXX9gdaNfHhsY4S8NFSYUucNXowY sQQ7HOKr+aoeE6Mri+UXKTqwhYrqVRoxCU+JMT88YA== X-Google-Smtp-Source: ABdhPJwV27iLXbdaB1RtNauLSUOg77V8YBWzHp7vs/k9WLRKvYJLHBpGZWmKqSB/SdqHqStRFh6K2k55TbQg+UQMFVg= X-Received: by 2002:ac2:54a4:: with SMTP id w4mr16239680lfk.254.1629713383593; Mon, 23 Aug 2021 03:09:43 -0700 (PDT) MIME-Version: 1.0 References: <20210820010403.946838-1-joshdon@google.com> <20210820010403.946838-5-joshdon@google.com> In-Reply-To: <20210820010403.946838-5-joshdon@google.com> From: Vincent Guittot Date: Mon, 23 Aug 2021 12:09:32 +0200 Message-ID: Subject: Re: [PATCH v3 4/4] sched: adjust sleeper credit for SCHED_IDLE entities To: Josh Don Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Paul Turner , Oleg Rombakh , Viresh Kumar , Steve Sistare , Tejun Heo , Rik van Riel , linux-kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 20 Aug 2021 at 03:04, Josh Don wrote: > > Give reduced sleeper credit to SCHED_IDLE entities. As a result, woken > SCHED_IDLE entities will take longer to preempt normal entities. > > The benefit of this change is to make it less likely that a newly woken > SCHED_IDLE entity will preempt a short-running normal entity before it > blocks. > > We still give a small sleeper credit to SCHED_IDLE entities, so that > idle<->idle competition retains some fairness. > > Example: With HZ=1000, spawned four threads affined to one cpu, one of > which was set to SCHED_IDLE. Without this patch, wakeup latency for the > SCHED_IDLE thread was ~1-2ms, with the patch the wakeup latency was > ~5ms. > > Signed-off-by: Josh Don Reviewed-by: Vincent Guittot > --- > kernel/sched/fair.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 31f40aa005b9..aa9c046d2aab 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4230,7 +4230,12 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) > > /* sleeps up to a single latency don't count. */ > if (!initial) { > - unsigned long thresh = sysctl_sched_latency; > + unsigned long thresh; > + > + if (se_is_idle(se)) > + thresh = sysctl_sched_min_granularity; > + else > + thresh = sysctl_sched_latency; > > /* > * Halve their sleep time's effect, to allow > -- > 2.33.0.rc2.250.ged5fa647cd-goog >