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=-2.4 required=3.0 tests=DKIM_SIGNED, 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 D0EDEC3279B for ; Mon, 2 Jul 2018 15:21:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A3A520C03 for ; Mon, 2 Jul 2018 15:21:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aCDPHOTY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8A3A520C03 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1752274AbeGBPVK (ORCPT ); Mon, 2 Jul 2018 11:21:10 -0400 Received: from mail-yb0-f193.google.com ([209.85.213.193]:40887 "EHLO mail-yb0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751443AbeGBPVJ (ORCPT ); Mon, 2 Jul 2018 11:21:09 -0400 Received: by mail-yb0-f193.google.com with SMTP id y11-v6so1725172ybm.7 for ; Mon, 02 Jul 2018 08:21:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=KjAU1n16nNiLQs4iuK4WOdn03VIJLmVf1f4XWDGd9ZU=; b=aCDPHOTYjHannO9MWJUDQl4I/43Og1SlrgDWncSxA0wrHrRg6PkPnXpldkSLS9No9h eoJoDNWOnnB9DeR6pRtp7IowFaewGtkTn2CTswb+RNHayOBePd8z30EmQ+MsoXHfO/Qo R26prDQGB+xYgBuaoaFeroXwF9KPMv/w93N2hh8X+HsWDB17sxy31QwV0J2pnGa/CA1q 1FhSMalg8vLMXthpLTv51APnbOLEfm0ljH+MeSLwUiwG0H10ZCe/wPVIANLrsq4LSGpr GNS7kfC+KsP6jlpy1qLbynUbJHReWQDUoZN1ZhnC/xPKAKclyJaIE5ty7+0/eEzbuvdE 8eGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=KjAU1n16nNiLQs4iuK4WOdn03VIJLmVf1f4XWDGd9ZU=; b=JFG7xFrh5wlrHDNH7dDVyijcbTdGBHh+BlqT2r+kr2YBNCOf+MhVelbmftejIwKsH6 2sasms1Oz/beDUXYMl479bhf60iXtYb/74plIXFd1MaMXuMum/SS4PYz4k+AaNcyERPw bOJDJfZooMnFY8/ErBtBS0Sw0Jdu02BsOP0JHYvzMCeBEND7pY3bfFo1q36zIP63HqRS FjnME4FOs7oNzClb+aN2NfhoTHkfZkZvh/Ks607NbRqDcne/GYOdXQUGGXYDjOXC4Kc7 is6CkbqkgFu/CAZbG86VHER/c5ERY32Ufgn2GSqjp6SOGVbxU9i5O9ahyPup2+oar6+/ 5ttA== X-Gm-Message-State: APt69E0/ssNqM+QjB6WnJdY3lJYfbIoj0N25/gYFqPnn9V/KHQPxbrfE gqkUVYQzRz2O619xJSurXJE= X-Google-Smtp-Source: AAOMgpeZWxaCkSPTvM/JLIj+ZMp16EVHAKq+MqnesUIdYWvc3z7IiwjeLLue8fRjoGxxy7A5Q9omng== X-Received: by 2002:a5b:841:: with SMTP id v1-v6mr11286591ybq.250.1530544868388; Mon, 02 Jul 2018 08:21:08 -0700 (PDT) Received: from localhost ([2620:10d:c091:200::2b6f]) by smtp.gmail.com with ESMTPSA id l14-v6sm6114604ywi.35.2018.07.02.08.21.07 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 02 Jul 2018 08:21:07 -0700 (PDT) Date: Mon, 2 Jul 2018 08:21:06 -0700 From: Tejun Heo To: Peter Zijlstra Cc: Xunlei Pang , Ingo Molnar , Frederic Weisbecker , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/cputime: Ensure correct utime and stime proportion Message-ID: <20180702152106.GD533219@devbig577.frc2.facebook.com> References: <20180622071542.61569-1-xlpang@linux.alibaba.com> <20180626154908.GE2458@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180626154908.GE2458@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Peter. On Tue, Jun 26, 2018 at 05:49:08PM +0200, Peter Zijlstra wrote: > Well, no, because the Changelog is incomprehensible and the patch > doesn't really have useful comments, so I'll have to reverse engineer > the entire thing, and I've just not had time for that. Just as an additional data point, we also sometimes see artifacts from cpu_adjust_time() in the form of per-task user or sys time getting stuck for some period (in extreme cases for over a minute) while the application isn't doing anything differently. We're telling the users that it's an inherent sampling artifact but it'd be nice to improve it if possible without adding noticeable overhead. No idea whether this patch's approach is a good one tho. Thanks. -- tejun