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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 1F215C38A2A for ; Fri, 8 May 2020 09:09:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA725208D6 for ; Fri, 8 May 2020 09:09:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PpEFd8FQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726811AbgEHJJq (ORCPT ); Fri, 8 May 2020 05:09:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725710AbgEHJJp (ORCPT ); Fri, 8 May 2020 05:09:45 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90DC9C05BD43 for ; Fri, 8 May 2020 02:09:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Xb+C9x4SIhmpbdhdXWMSHO37biGDOHtvQ/W2i8m4dTo=; b=PpEFd8FQp6vNcOZNu0Da+9bMtN ni4z8WEXHbTgTA/hc+iJOW5x9YzTaZGBxvGXE0nAMoMgl1bv7rVhPRZICHOpI+3E1SmxpOo4lsXp5 tgWZ9jwG5edPLnkQDPx+jzc1rFXgKXYxM+3O5svw0NqHXy52TeQCEQkxwAc9J4u82MgPzx/AfKRvN omg53m7OHKaJ9Sgdn1MesdG0HiOKnERmt2/T44n2nYYhP5w+3IZ8QrtNtowI7LaTG7TmkEAOrSnjx X/rVrEv3u3zPcMCnhkVODO25lHbaM+cecIk2taXFGHLWOasfNHX/paoS+/OCP7eje7t6u4EobX3zC WYEtHesQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWz0b-0007QA-9s; Fri, 08 May 2020 09:09:29 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A776A301DFC; Fri, 8 May 2020 11:09:25 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6C9942B93BDCE; Fri, 8 May 2020 11:09:25 +0200 (CEST) Date: Fri, 8 May 2020 11:09:25 +0200 From: Peter Zijlstra To: Aaron Lu Cc: Vineeth Remanan Pillai , Nishanth Aravamudan , Julien Desfossez , Tim Chen , Ingo Molnar , Thomas Gleixner , Paul Turner , Linus Torvalds , Aaron Lu , Linux List Kernel Mailing , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Kees Cook , Greg Kerr , Phil Auld , Aubrey Li , "Li, Aubrey" , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , Joel Fernandes , Joel Fernandes Subject: Re: [PATCH updated v2] sched/fair: core wide cfs task priority comparison Message-ID: <20200508090925.GV5298@hirez.programming.kicks-ass.net> References: <20200415033408.GA168322@ziqianlu-desktop.localdomain> <20200415040741.GA169001@ziqianlu-desktop.localdomain> <20200417094045.GA197704@ziqianlu-desktop.localdomain> <20200420080759.GA224731@ziqianlu-desktop.localdomain> <20200421025131.GA227300@aaronlu-desktop> <20200424142443.GA263207@aaronlu-desktop> <20200506143506.GH5298@hirez.programming.kicks-ass.net> <20200508084419.GA120223@aaronlu-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200508084419.GA120223@aaronlu-desktop> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 08, 2020 at 04:44:19PM +0800, Aaron Lu wrote: > On Wed, May 06, 2020 at 04:35:06PM +0200, Peter Zijlstra wrote: > > Aside from this being way to complicated for what it does -- you > > could've saved the min_vruntime for each rq and compared them with > > subtraction -- it is also terminally broken afaict. > > > > Consider any infeasible weight scenario. Take for instance two tasks, > > each bound to their respective sibling, one with weight 1 and one with > > weight 2. Then the lower weight task will run ahead of the higher weight > > task without bound. > > I don't follow how this could happen. Even the lower weight task runs > first, after some time, the higher weight task will get its turn and > from then on, the higher weight task will get more chance to run(due to > its higher weight and thus, slower accumulation of vruntime). That seems to assume they're mutually exclusive. In that case, as I argued, we only have a single runqueue and then yes it works. But if they're not exclusive, and can run concurrently, it comes apart.