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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 7A1F8C2D0C9 for ; Thu, 12 Dec 2019 11:20:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CB2422527 for ; Thu, 12 Dec 2019 11:20:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="ejIqzn/R" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728959AbfLLLUP (ORCPT ); Thu, 12 Dec 2019 06:20:15 -0500 Received: from mail-lj1-f194.google.com ([209.85.208.194]:36891 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728953AbfLLLUO (ORCPT ); Thu, 12 Dec 2019 06:20:14 -0500 Received: by mail-lj1-f194.google.com with SMTP id u17so1855961lja.4 for ; Thu, 12 Dec 2019 03:20:13 -0800 (PST) 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=P1W0z4HqV64jzJwtaYcGadzOgRZCn2v4chbYC9m9FGs=; b=ejIqzn/RWAjyKo7RBVFzhGkFkF2lSZiGd2eJMd8SI1r0ISOjFbygsYsgAQN8XmQzQk 0lLFXQhwKM1eITsy4avAQxAh9YW73FCSxA30SOO4ebLCpg54/FqhH1kVEkL7cqr550+3 I9a9nPQN0ywXQrPzcfOaggdXetKiYHLmJjI+1DZc9EUMx2O/iWPayKLBlkjZYv4V8NgJ nan9YSgU3ufNHuyQvCbLyfmekHqbVqfxJNEwf9KzEqsovts3q/fPjhlFqhuzDFb1nWyW xAcA0eUqzW/MADBAAmUvKLx8NNJDQc7mcfuqeaYrbAn5Geo/v9v5h5dAUr3AVBKVcV47 h5mw== 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=P1W0z4HqV64jzJwtaYcGadzOgRZCn2v4chbYC9m9FGs=; b=MdV4igd1GigfNvpC4sDe0d0boAhml0sSKxd+WZcy6bxauGl/6kfXapUnW76WmK9E+k kTazdO4BWTu8CCEAKRaOqLDsfakZCWMSzvaNlRT7VyvGepWdrW8kHlwwF9pX5fjkA5WN AxpzrEJ35jXIzuKPQD4xz3pcTWKapuA8H/4p4uKAYSfWkdm/JBOUS6D1nTDLftRzYzI6 GM19GcUbsO4Pdpxa/aIJ89X0v7TLyKJn5m3tGDV1cP9S6MnFcQFWoXNhh1xv54/993aU oiU36B6hsmdENuaGfStuVSYgbjkhRemCUiWZTu1vH81688KUv/NjEzjciPcHtSOYv6FK hiFg== X-Gm-Message-State: APjAAAXTJrrPTYpPKVa20pOpTmlJwbpFv2WYjU5jayTfV56BZD+yflVL RIWw4yyc7F8usqos8x0pcRgShoX2wp/9bm6BVX8/EbhBzek= X-Google-Smtp-Source: APXvYqwcNMZYiNwnTt8iXUn4bZLBe/VVIuZbWOxdaGwBRPCIZF6vo/z0Flel1o/NxhVXsNhFkAgOrX3kstFVUuexBm4= X-Received: by 2002:a2e:9a51:: with SMTP id k17mr5118022ljj.206.1576149612570; Thu, 12 Dec 2019 03:20:12 -0800 (PST) MIME-Version: 1.0 References: <20191120220313.GC18056@pauld.bos.csb> <20191121132937.GW4114@hirez.programming.kicks-ass.net> <20191209165122.GA27229@linux.vnet.ibm.com> <20191209231743.GA19256@dread.disaster.area> <20191210054330.GF27253@linux.vnet.ibm.com> <20191210172307.GD9139@linux.vnet.ibm.com> <20191211173829.GB21797@linux.vnet.ibm.com> <20191211224617.GE19256@dread.disaster.area> <20191212101031.GV2827@hirez.programming.kicks-ass.net> <20191212101424.GH2871@hirez.programming.kicks-ass.net> <20191212102327.GI2871@hirez.programming.kicks-ass.net> In-Reply-To: <20191212102327.GI2871@hirez.programming.kicks-ass.net> From: Vincent Guittot Date: Thu, 12 Dec 2019 12:20:01 +0100 Message-ID: Subject: Re: [PATCH v4] sched/core: Preempt current task in favour of bound kthread To: Peter Zijlstra Cc: Dave Chinner , Srikar Dronamraju , Phil Auld , Ming Lei , linux-block , linux-fs , linux-xfs , linux-kernel , Jeff Moyer , Dave Chinner , Eric Sandeen , Christoph Hellwig , Jens Axboe , Ingo Molnar , Tejun Heo Content-Type: text/plain; charset="UTF-8" Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, 12 Dec 2019 at 11:23, Peter Zijlstra wrote: > > On Thu, Dec 12, 2019 at 11:14:24AM +0100, Peter Zijlstra wrote: > > On Thu, Dec 12, 2019 at 11:10:31AM +0100, Peter Zijlstra wrote: > > > @@ -4156,13 +4159,13 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > > > if (delta_exec < sysctl_sched_min_granularity) > > > return; > > > > > > - se = __pick_first_entity(cfs_rq); > > > + se = __pick_next_entity(cfs_rq, NULL); > > > delta = curr->vruntime - se->vruntime; > > > > > > if (delta < 0) > > > return; > > > > What I mean with the below comment is, when this isn't enough, try > > something like: > > > > if (se == cfs_rq->next) > > ideal_runtime /= 2; > > > > to make it yield sooner to 'next' buddies. Sadly, due to the whole > > cgroup mess, we can't say what actual task is on the end of it (without > > doing a full hierarchy pick, which is more expensive still). > > Just for giggles, that'd look something like: > > while (!entity_is_task(se) { > cfs_rq = group_cfs_rq(se); > se = pick_next_entity(cfs_rq, cfs_rq->curr); > } > p = task_of(se); > > if (is_per_cpu_kthread(p)) > ideal_runtime /= 2; > > the core-scheduling patch set includes the right primitive for this I > think, pick_task_fair(). why not only updating wan_gran() which is the only function which uses sysctl_sched_wakeup_granularity ? For per cpu kthread, we could set the gran to sched_min_granularity instead of scaling it with thread's priority so per cpu kthread can still preempt current ask even if sysctl_sched_wakeup_granularity is large > > > > - if (delta > ideal_runtime) > > > + if (delta > ideal_runtime) // maybe frob this too ? > > > resched_curr(rq_of(cfs_rq)); > > > }