From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752204Ab1AVVXQ (ORCPT ); Sat, 22 Jan 2011 16:23:16 -0500 Received: from mail-iw0-f174.google.com ([209.85.214.174]:51854 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750956Ab1AVVXP (ORCPT ); Sat, 22 Jan 2011 16:23:15 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:subject:from:to:cc:in-reply-to:references :mime-version; b=YSdkFdVzAaNiIBebkj+EYm0CiraiNlLjVwpC0BOxRhpl8u/a6/0bPUhV4cTXYjx3KA CIbsf4rhqDzRgzJx0fKv1etM7zLym15Z+cryJKnMjzSG1cPBFit3Og2EFlCY1ApzYB7i C9L2LPuoVwHfn8Te73Gq+ITdAphYi9ZrKIuTo= Message-ID: <4d3b4ac1.26092a0a.6f30.ffffcf6b@mx.google.com> Date: Sat, 22 Jan 2011 13:23:13 -0800 (PST) Subject: Re: 'autogroup' sched code KILLING responsiveness From: Michael Witten To: Mike Galbraith Cc: linux-kernel@vger.kernel.org In-Reply-To: <1295648870.23779.15.camel@marge.simson.net> References: <4d39ce58.cc7e0e0a.5448.59e4@mx.google.com> <1295648870.23779.15.camel@marge.simson.net> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 21 Jan 2011 23:27:50 +0100, Mike Galbraith wrote: >On Fri, 2011-01-21 at 10:20 -0800, Michael Witten wrote: >> Bisecting shows that this commit: >> >> 5091faa449ee0b7d73bc296a93bca9540fc51d0a >> sched: Add 'autogroup' scheduling feature: automated per session task groups >> Date: Tue Nov 30 14:18:03 2010 +0100 >> >> is the reason that my computer has become unusable. >> >> With that code in place, a resource-intensive activity (such as >> compiling the Linux kernel) causes my computer to become >> unresponsive for many seconds at a time; the entire screen >> does not refresh, typed keys are dropped or are handled very >> late, etc (even in Linux's plain virtual consoles). > > That's not what I'm experiencing with a UP kernel... Firstly, I apologize for the rather unhelpful email that follows. On my machine (x86, Dell Latitude D810), the problem is so incredibly debilitating that it is incomprehensible others would not notice if they were subject to the same problem; basically, I don't know what to do at this point (I've played around with `oprofile' and `tools/perf', but nothing looks very odd to me either). I'd appreciate it if you could give me some direction; I wish I could give you more with which to work. Should I send you a copy of my kernel configuration? (I was going to inline it, as well as the results of `lspci' and `cat /proc/cpuinfo', but I thought that might be unhelpful if not rude). Invariably, running: yes in a Linux virtual console completely locks me out of my system (it's not even possible to login remotely via ssh); however, running it within a terminal emulator in X doesn't seem to cause the problems I've been seeing. Things get stranger. When I run the following in a Linux VC: sleep 10; yes | head -2500000 and then switch to X before `yes' begins to run, I can move my mouse cursor around without trouble for the entire time that `yes' is allowed to run. HOWEVER, if I ever press (and release if you like) a key on my keyboard while `yes' is running, then the entire screen freezes, including the mouse cursor; I only regain control when `yes' finishes. Similarly, if I build the Linux kernel: make (this time even within a terminal emulator in X), then I can move my mouse cursor around without trouble UNTIL I also press keyboard keys (actually, I'm just holding one key down), at which point the mouse cursor periodically freezes; the whole screen freezes with each new status line of the build and then briefly unfreezes before the next status line can appear (that is, before the next file can be compiled); the indications are that nothing else is getting the CPU, as keypresses are sometimes dropped. Of course, I have none of these problems when I disable: CONFIG_AUTOGROUP_SCHED Sincerely, Michael Witten