From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S275074AbTHLHHk (ORCPT ); Tue, 12 Aug 2003 03:07:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S275079AbTHLHHk (ORCPT ); Tue, 12 Aug 2003 03:07:40 -0400 Received: from dyn-ctb-210-9-241-99.webone.com.au ([210.9.241.99]:42758 "EHLO chimp.local.net") by vger.kernel.org with ESMTP id S275074AbTHLHHh (ORCPT ); Tue, 12 Aug 2003 03:07:37 -0400 Message-ID: <3F389221.6080202@cyberone.com.au> Date: Tue, 12 Aug 2003 17:07:13 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3.1) Gecko/20030618 Debian/1.3.1-3 X-Accept-Language: en MIME-Version: 1.0 To: Mike Galbraith CC: rob@landley.net, Con Kolivas , linux kernel mailing list , Andrew Morton , Ingo Molnar , Felipe Alfaro Solana Subject: Re: [PATCH] O13int for interactivity References: <200308110248.09399.rob@landley.net> <200308050207.18096.kernel@kolivas.org> <200308052022.01377.kernel@kolivas.org> <3F2F87DA.7040103@cyberone.com.au> <200308110248.09399.rob@landley.net> <5.2.1.1.2.20030812075224.01988de8@pop.gmx.net> In-Reply-To: <5.2.1.1.2.20030812075224.01988de8@pop.gmx.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Mike Galbraith wrote: > At 12:51 PM 8/12/2003 +1000, Nick Piggin wrote: > > >> Rob Landley wrote: >> >>> On Tuesday 05 August 2003 06:32, Nick Piggin wrote: >>> >>> >>>> But by employing the kernel's services in the shape of a blocking >>>> syscall, all sleeps are intentional. >>> >>> >>> Wrong. Some sleeps indicate "I have run out of stuff to do right >>> now, I'm going to wait for a timer or another process or something >>> to wake me up with new work". >>> >>> >>> >>> Some sleeps indicate "ideally this would run on an enormous ramdisk >>> attached to gigabit ethernet, but hard drives and internet >>> connections are just too slow so my true CPU-hogness is hidden by >>> the fact I'm running on a PC instead of a mainframe." >> >> >> I don't quite understand what you are getting at, but if you don't >> want to >> sleep you should be able to use a non blocking syscall. But in some >> cases >> I think there are times when you may not be able to use a non >> blocking call. >> And if a process is a CPU hog, its a CPU hog. If its not its not. >> Doesn't >> matter how it would behave on another system. > > > Ah, but there is something there. Take the X and xmms's gl thread > thingy I posted a while back. (X runs long enough to expire in the > presence of a couple of low priority cpu hogs. gl thread, which is a > mondo cpu hog, and normally runs and runs and runs at cpu hog > priority, suddenly acquires extreme interactive priority, and X, which > is normally sleepy suddenly becomes permanently runnable at cpu hog > priority) The gl thread starts sleeping because X isn't getting > enough cpu to be able to get it's work done and go to sleep. The gl > thread isn't voluntarily sleeping, and X isn't voluntarily running. > The behavior change is forced upon both. It does... It is I tell ya! Look, the gl thread is probably _very_ explicitly asking to sleep. No I don't know how X works, but I have an idea that select is generally used as an event notification, right? Now the gl thread is essentially saying "wait until X finishes the work I've given it, or I get some other event": ie. "put me to sleep until this fd becomes readable". OK maybe your scenario is a big problem. Its not due to any imagined semantics in the way things are sleeping. Its due to the scheduler.