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=-14.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_IN_DEF_DKIM_WL 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 627BFC282DA for ; Wed, 17 Apr 2019 23:08:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3378F2183F for ; Wed, 17 Apr 2019 23:08:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pBw+np0n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387702AbfDQXIC (ORCPT ); Wed, 17 Apr 2019 19:08:02 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:36595 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387617AbfDQXIB (ORCPT ); Wed, 17 Apr 2019 19:08:01 -0400 Received: by mail-wr1-f66.google.com with SMTP id y13so459822wrd.3 for ; Wed, 17 Apr 2019 16:08:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=m0+XMLd9YsaoHc4iKK68JAe8iNUvJjRM/ShPYIP04nk=; b=pBw+np0nsENmTaXuAa3htCqg4W2eEQV4XWA++dkWlgrXQUvfCAnjSTir3MFBBEAyYO 07CE45zMHxFjD763shuTNYuRCLJ8o2skqdab5DW0KrUhJTscWz6P5IAnkbOrq8yUTm43 2fYHLFKyzn468+BjO1Vh7N/UhGOKfn+vTQIAKC8dQBAZPvEXxAwXOAvROfJEs7jhJ4Qk c95eTrgjWOdibkzRWNw9129Ybd8vUeI7PAWMYhuPx38+BXDtd5WJu0a0kSRAXM8pNmWg 91VHPaEmv8ZUCQc+q0CAQOUS325DFVVy/f7tb/+CbZ/41dEFGee0wl7mcRhsA21QhMFL bFxg== 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=m0+XMLd9YsaoHc4iKK68JAe8iNUvJjRM/ShPYIP04nk=; b=C+Pt+3Qvd51TT/UbankYycXUWb804elBaSVNAtqQ9l0upNtvsP0ANdo3eqxGc3KmfE b3xpAU0aKfvPm5akwXlBvs7KzdQGescTPxBmCZBIZSLYq03wyqc3md+PXyRtPJb6Vl5T 0xQJnUEuxx09SDhFHlHcT2HT6J7kstUNf/mFHE1VJtXcq+a9el7/1yKNG1AVUSwDKQRF +ABq/HEtpE+CbVlETJBgnC90DgUCUtJD5NnTVxAxrfj1XxCOO65KAVHSvqtoB6M9jIW/ 0XJp0wStLFqr0uYO97WnYoHrrPrZCIQBwvB4ffg2iWYzIgwM+u5mFE9N6IKt3d9lL+u5 rsYA== X-Gm-Message-State: APjAAAUh9GKmxufY4lWuw/lwNGYNrtNUw471OjHLboW4cPPnr1RYG9bG 4QduY118jjqQeD4BQUt4QzdeufCXZnxVEAEYf9IT2A== X-Google-Smtp-Source: APXvYqzFOHyqZUZ5RJ93xh1sS/UW+R6siuj863T4cJnREaeiWM5+qkieXfJvd9nA04+h0VrJGd5Q61w6NpRpJiWIFXg= X-Received: by 2002:a5d:4f8b:: with SMTP id d11mr28114025wru.150.1555542479268; Wed, 17 Apr 2019 16:07:59 -0700 (PDT) MIME-Version: 1.0 References: <20190402104153.25404-1-patrick.bellasi@arm.com> <20190402104153.25404-9-patrick.bellasi@arm.com> In-Reply-To: <20190402104153.25404-9-patrick.bellasi@arm.com> From: Suren Baghdasaryan Date: Wed, 17 Apr 2019 16:07:48 -0700 Message-ID: Subject: Re: [PATCH v8 08/16] sched/core: uclamp: Set default clamps for RT tasks To: Patrick Bellasi Cc: LKML , linux-pm@vger.kernel.org, linux-api@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 2, 2019 at 3:42 AM Patrick Bellasi wrote: > > By default FAIR tasks start without clamps, i.e. neither boosted nor > capped, and they run at the best frequency matching their utilization > demand. This default behavior does not fit RT tasks which instead are > expected to run at the maximum available frequency, if not otherwise > required by explicitly capping them. > > Enforce the correct behavior for RT tasks by setting util_min to max > whenever: > > 1. the task is switched to the RT class and it does not already have a > user-defined clamp value assigned. > > 2. an RT task is forked from a parent with RESET_ON_FORK set. > > NOTE: utilization clamp values are cross scheduling class attributes and > thus they are never changed/reset once a value has been explicitly > defined from user-space. > > Signed-off-by: Patrick Bellasi > Cc: Ingo Molnar > Cc: Peter Zijlstra > --- > kernel/sched/core.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index bdebdabe9bc4..71c9dd6487b1 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1042,6 +1042,28 @@ static int uclamp_validate(struct task_struct *p, > static void __setscheduler_uclamp(struct task_struct *p, > const struct sched_attr *attr) > { > + unsigned int clamp_id; > + > + /* > + * On scheduling class change, reset to default clamps for tasks > + * without a task-specific value. > + */ > + for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) { > + struct uclamp_se *uc_se = &p->uclamp_req[clamp_id]; > + unsigned int clamp_value = uclamp_none(clamp_id); > + > + /* Keep using defined clamps across class changes */ > + if (uc_se->user_defined) > + continue; > + > + /* By default, RT tasks always get 100% boost */ > + if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) > + clamp_value = uclamp_none(UCLAMP_MAX); > + > + uc_se->bucket_id = uclamp_bucket_id(clamp_value); > + uc_se->value = clamp_value; Is it possible for p->uclamp_req[UCLAMP_MAX].value to be less than uclamp_none(UCLAMP_MAX) for this RT task? If that's a possibility then I think we will end up with a case of p->uclamp_req[UCLAMP_MIN].value > p->uclamp_req[UCLAMP_MAX].value after these assignments are done. > + } > + > if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) > return; > > @@ -1077,6 +1099,10 @@ static void uclamp_fork(struct task_struct *p) > for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) { > unsigned int clamp_value = uclamp_none(clamp_id); > > + /* By default, RT tasks always get 100% boost */ > + if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) > + clamp_value = uclamp_none(UCLAMP_MAX); > + > p->uclamp_req[clamp_id].user_defined = false; > p->uclamp_req[clamp_id].value = clamp_value; > p->uclamp_req[clamp_id].bucket_id = uclamp_bucket_id(clamp_value); > -- > 2.20.1 >