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=-12.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1, USER_IN_DEF_DKIM_WL 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 5DF79C33C9E for ; Wed, 8 Jan 2020 09:51:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32B2C20848 for ; Wed, 8 Jan 2020 09:51:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="wFe4jLFl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727036AbgAHJvO (ORCPT ); Wed, 8 Jan 2020 04:51:14 -0500 Received: from mail-wr1-f66.google.com ([209.85.221.66]:46455 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726556AbgAHJvO (ORCPT ); Wed, 8 Jan 2020 04:51:14 -0500 Received: by mail-wr1-f66.google.com with SMTP id z7so2574026wrl.13 for ; Wed, 08 Jan 2020 01:51:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=SYIX5lCn201jIdgFI8cXaaFqyTSNVacx0tO+JKzdFG8=; b=wFe4jLFlUg6FK/9/5dItkW8JnJTzFY6w0imwJZ4kbornDo9YbT0RTpZrEXYpRk3f2+ LbZP1U3K/1Lxn/KAIeCt9oa6+rXtwlLJqhrhfukloDcA4lwxBCaoUawe2cJnb+XvkI0s MsvlKQuetVXhoYv9leB4T/Ue6x3fCj4Y6ayzOo8x2ikfD7GhXK0OjdkR2PVp8RWqF6Mx ncaY+Spy4k/ppc6qECRxF3IKEUsaZEh9onRO5Wv99KmxM79jC+rfAkkKbPNf+EtVzlK2 7gJ+PwLkSl+PYgIqgq+DOvQL6kh3W2L6cspPM5q43ZQiUis1/byKsxDf/j9lkw5im1Ki hX/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=SYIX5lCn201jIdgFI8cXaaFqyTSNVacx0tO+JKzdFG8=; b=E/zFG18w9M9vME83Gkwqb/ZtFeECr73eykwNNbw0OtOyUYLM6XTfKMnySkMQmlw/mo AnCNDEwAqI2fP/6wH6P+TXx9glyYoBLhtKTVOfTx6+xMctwLVlSPSzSwnjFP8hAbX4Vh f79q8fsXZ7ZKHZCUB3HZgVDLK8i1ioURqbtSmR3iA53M0orP2x/G9UbTV/axKhDG1YQ3 i3FS1hWbTwt5CeWU86+/7e6aah6zd2AKto95r4m2S7ARxONkWEDwYgM4uGQ5Pg1YzsGz liEpm68k+ZT+vf9/y5D+YiXUvJsLQ87wAxtyaTrkhc1biVceE2u0+2UW8Oq15ENZzMWp WjPQ== X-Gm-Message-State: APjAAAUyIgfAQXcWV3KCyK3dF+GXtAjFyxboLfzOW5xk32orduOGHF6d 0oAG5YDE3LzcR7P1QF1BM49kMQ== X-Google-Smtp-Source: APXvYqwpJ/qkuF9mN7qO3XblBcRL45/iYNNTuD+IaCRUy2rP1dYfdG9lOJlJx+LEbkSUEDmE7Q8jWA== X-Received: by 2002:adf:e3d0:: with SMTP id k16mr3557559wrm.241.1578477072161; Wed, 08 Jan 2020 01:51:12 -0800 (PST) Received: from google.com ([2a00:79e0:d:110:d6cc:2030:37c1:9964]) by smtp.gmail.com with ESMTPSA id z83sm3276181wmg.2.2020.01.08.01.51.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jan 2020 01:51:11 -0800 (PST) Date: Wed, 8 Jan 2020 09:51:08 +0000 From: Quentin Perret To: Dietmar Eggemann Cc: Qais Yousef , Ingo Molnar , Peter Zijlstra , Steven Rostedt , Luis Chamberlain , Kees Cook , Iurii Zaikin , Juri Lelli , Vincent Guittot , Ben Segall , Mel Gorman , valentin.schneider@arm.com, Patrick Bellasi , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH] sched/rt: Add a new sysctl to control uclamp_util_min Message-ID: <20200108095108.GA153171@google.com> References: <20191220164838.31619-1-qais.yousef@arm.com> <20200107134234.GA158998@google.com> <8bb17e84-d43f-615f-d04d-c36bb6ede5e0@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8bb17e84-d43f-615f-d04d-c36bb6ede5e0@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 07 Jan 2020 at 20:30:36 (+0100), Dietmar Eggemann wrote: > On 07/01/2020 14:42, Quentin Perret wrote: > > Hi Qais, > > > > On Friday 20 Dec 2019 at 16:48:38 (+0000), Qais Yousef wrote: > > [...] > > >> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > >> index e591d40fd645..19572dfc175b 100644 > >> --- a/kernel/sched/rt.c > >> +++ b/kernel/sched/rt.c > >> @@ -2147,6 +2147,12 @@ static void pull_rt_task(struct rq *this_rq) > >> */ > >> static void task_woken_rt(struct rq *rq, struct task_struct *p) > >> { > >> + /* > >> + * When sysctl_sched_rt_uclamp_util_min value is changed by the user, > >> + * we apply any new value on the next wakeup, which is here. > >> + */ > >> + uclamp_rt_sync_default_util_min(p); > > > > The task has already been enqueued and sugov has been called by then I > > think, so this is a bit late. You could do that in uclamp_rq_inc() maybe? > > That's probably better. > Just to be sure ...we want this feature (an existing rt task gets its > UCLAMP_MIN value set when the sysctl changes) because there could be rt > tasks running before the sysctl is set? Yeah, I was wondering the same thing, but I'd expect sysadmin to want this. We could change the min clamp of existing RT tasks in userspace instead, but given how simple Qais' lazy update code is, the in-kernel looks reasonable to me. No strong opinion, though. Thanks, Quentin