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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 E9831C6778C for ; Thu, 5 Jul 2018 13:42:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A2DB22403B for ; Thu, 5 Jul 2018 13:42:29 +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="1xQlhg6C" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2DB22403B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753838AbeGENm0 (ORCPT ); Thu, 5 Jul 2018 09:42:26 -0400 Received: from merlin.infradead.org ([205.233.59.134]:47636 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753715AbeGENmW (ORCPT ); Thu, 5 Jul 2018 09:42:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=bvwm6cGrD+353JcOrWu68PkLpub8x8Y6JsoIybI8aR8=; b=1xQlhg6CRetk+8HqW6S7boP8M Jq7p8oCjar0X4g3iTFxuSRsjN5koNhdBlyDnP4aVen6jb7VW+qjbBwdfdcFJtDsr/KkMGc2C//lmJ 26vaCsjW7Ig1Pb/LcUzWHMS4um6cP5HrdQZgE/Nv+ydQVmMNX7gNUJ8ZaEzH4OP3sdcv7+ibLpiqH cu17TI8gqzN5DTSdpf8PlZ0RCImcobDRxB5r7frOfkLW/PwCpOujYHXzeRygRjt2lgGT3OTgdC3u0 eXHA95DzQ7wE8HeP/KCILCI1ZokgHt8txTHCFnVhh1E3Rn7v4jzrtLSpCnEQr/gu2iOMtZrjJLK/b ea0SVE+pQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fb4WX-0007zc-Kj; Thu, 05 Jul 2018 13:42:17 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 613AD20298BAE; Thu, 5 Jul 2018 15:42:14 +0200 (CEST) Date: Thu, 5 Jul 2018 15:42:14 +0200 From: Peter Zijlstra To: Xunlei Pang Cc: Ingo Molnar , Frederic Weisbecker , Tejun Heo , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/cputime: Ensure correct utime and stime proportion Message-ID: <20180705134214.GF2494@hirez.programming.kicks-ass.net> References: <20180622071542.61569-1-xlpang@linux.alibaba.com> <20180626154908.GE2458@hirez.programming.kicks-ass.net> <20180705104632.GE2494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 05, 2018 at 09:21:15PM +0800, Xunlei Pang wrote: > On 7/5/18 6:46 PM, Peter Zijlstra wrote: > > On Wed, Jun 27, 2018 at 08:22:42PM +0800, Xunlei Pang wrote: > >> tick-based whole utime is utime_0, tick-based whole stime > >> is stime_0, scheduler time is rtime_0. > > > >> For a long time, the process runs mainly in userspace with > >> run-sleep patterns, and because two different clocks, it > >> is possible to have the following condition: > >> rtime_0 < utime_0 (as with little stime_0) > > > > I don't follow... what? > > > > Why are you, and why do you think it makes sense to, compare rtime_0 > > against utime_0 ? > > > > The [us]time_0 are, per your earlier definition, ticks. They're not an > > actual measure of time. Do not compare the two, that makes no bloody > > sense. > > > > [us]time_0 is task_struct:utime{stime}, I cited directly from > cputime_adjust(), both in nanoseconds. I assumed "rtime_0 < utime_0" > here to simple the following proof to help explain the problem we met. In the !VIRT_CPU_ACCOUNTING case they (task_struct::[us]time) are not actual durations. Yes, the happen to be accounted in multiples of TICK_NSEC and thereby happen to carry a [ns] unit, but they are not durations, they are samples. (we just happen to store them in a [ns] unit because for VIRT_CPU_ACCOUNTING they are in fact durations) If 'rtime < utime' is not a valid assumption to build a problem on for !VIRT_CPU_ACCOUNTING. So please try again, so far you're not making any sense.