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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45B22C4332F for ; Mon, 12 Dec 2022 20:15:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233570AbiLLUPz (ORCPT ); Mon, 12 Dec 2022 15:15:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231770AbiLLUP1 (ORCPT ); Mon, 12 Dec 2022 15:15:27 -0500 Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D1362B0; Mon, 12 Dec 2022 12:15:10 -0800 (PST) Received: by mail-pl1-x62e.google.com with SMTP id p24so13280892plw.1; Mon, 12 Dec 2022 12:15:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=+FHYQaECelaNtH5CB2bDo9uLzM9I49pjKixgEBaWRB8=; b=QBGGYFbr/Z82wnD98tLRe5+Xp2cudBtrbuEl1W4I9oF7ooOMtIzOsJNOlFDe9Jq51F mALPCy4pWnkD1rReho/uV7Fps3iu6KiLWL9bcPkOhcWpIAEVbisJS24ACbFQaTPSXwnk 1pky+vYyDMJuNjL9koaEJONjvU8Li8MikL1IseAio1hvxffNSmq8mMmNXZFlMYwDuqP1 aN0aAodRUh5pzUNckoaV5nYfE8fZfIw/tje2pX2Xvfel4Tin+ulJ4FPBeeGpGlbpTPUH 0xaxflIR0c+Ofx+MytD0HR3A1jXdlOtLWmbt191vuK68BIslhMDm12C26UqYH1u3QUiu d7jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=+FHYQaECelaNtH5CB2bDo9uLzM9I49pjKixgEBaWRB8=; b=Kr7B8hkOOWvOMFcyhLjI3VO9YG0Ms75i7WJqNyp/GtDhmOCP4fC2pF271iUZmRZyai AQDfQziTkbg9AKV+dUhois3YZ2OJ1Oyvbuw8abPPc86mlKpTstHWMSJkfMDbzb0yJhIN 0JsziPNIF3L3+q0wzqfkwpYMAS+WkQT4OgVx2i5YKaXCogslJqoSZDDJzpsGVfKn+ETb J2kr9orSD8LbtWMvEcewgO8RKeNr4cul0wJDgev0oZQw+yVkCDOX0KLXlcILPzSvyUuo zeYY+Ik0Q1pJ4BEyLJHFgmeUEKGmy7PAgznDgB9uM+2OrKCKlv273AYHdBOybBKcnnK5 RUUQ== X-Gm-Message-State: ANoB5pliLmpDo1kjgehQRSgs2Zjmmggjapk/eQRQfvI8w/cwVXKlF5fW nkfCmKvA5MZPUDZkKVEQw58= X-Google-Smtp-Source: AA0mqf5+IAeUPcqbnskdQ+WsN57U+BsRDb3McUq1ect6XnQsqta6yy6hwk6MqYK/n9klF3mr9TlTZw== X-Received: by 2002:a17:90a:af84:b0:218:c8fd:c213 with SMTP id w4-20020a17090aaf8400b00218c8fdc213mr18224585pjq.36.1670876109548; Mon, 12 Dec 2022 12:15:09 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id s1-20020a63f041000000b0045ff216a0casm5578797pgj.3.2022.12.12.12.15.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 12:15:09 -0800 (PST) Sender: Tejun Heo Date: Mon, 12 Dec 2022 10:15:07 -1000 From: Tejun Heo To: Peter Zijlstra Cc: torvalds@linux-foundation.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, joshdon@google.com, brho@google.com, pjt@google.com, derkling@google.com, haoluo@google.com, dvernet@meta.com, dschatzberg@meta.com, dskarlat@cs.cmu.edu, riel@surriel.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 05/31] sched: Add sched_class->reweight_task() Message-ID: References: <20221130082313.3241517-1-tj@kernel.org> <20221130082313.3241517-6-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 12, 2022 at 09:11:36PM +0100, Peter Zijlstra wrote: > > > Hurmph.. this further propagate the existing problem of thinking that > > > 'prio' is a useful concept in general (it isn't). > > > > I'm not quite following. Can you please expand on why prio isn't a generally > > useful concept? > > The whole fixed vs dynamic priority scheduling thing. Specifically > SCHED_DEADLINE implements a dynamic priority scheme using the sporadic > task model which just doesn't map well to this single prio value > (notably every SCHED_DEADLINE task has prio -1, making it impossible to > order SCHED_DEADLINE tasks based on this). I see, so the expressive power isn't sufficient to cover some use cases. Yeah, I mean, it's limited and we can add whatever that's necessary but given that there are many use cases that make use of priorities, I don't think SCX can skip supporting it. Thanks. -- tejun