From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993232AbXDSLud (ORCPT ); Thu, 19 Apr 2007 07:50:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2993238AbXDSLud (ORCPT ); Thu, 19 Apr 2007 07:50:33 -0400 Received: from omta05sl.mx.bigpond.com ([144.140.93.195]:25907 "EHLO omta05sl.mx.bigpond.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2993232AbXDSLuc (ORCPT ); Thu, 19 Apr 2007 07:50:32 -0400 Message-ID: <4627577B.7050204@bigpond.net.au> Date: Thu, 19 Apr 2007 21:50:19 +1000 From: Peter Williams User-Agent: Thunderbird 1.5.0.10 (X11/20070302) MIME-Version: 1.0 To: William Lee Irwin III CC: Ingo Molnar , Andrew Morton , Nick Piggin , Linus Torvalds , Matt Mackall , Mike Galbraith , Con Kolivas , ck list , Bill Huey , linux-kernel@vger.kernel.org, Arjan van de Ven , Thomas Gleixner Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS] References: <20070417070155.GF1057@wotan.suse.de> <20070417213954.GE11166@waste.org> <20070418031511.GA18452@wotan.suse.de> <20070418043831.GR11115@waste.org> <20070418050024.GF18452@wotan.suse.de> <20070418055525.GS11115@waste.org> <20070419031807.GA24512@wotan.suse.de> <20070418221432.e4dbcf4f.akpm@linux-foundation.org> <20070419063810.GA22418@elte.hu> <20070419075746.GD31925@holomorphy.com> In-Reply-To: <20070419075746.GD31925@holomorphy.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Authentication-Info: Submitted using SMTP AUTH PLAIN at oaamta07sl.mx.bigpond.com from [58.164.138.40] using ID pwil3058@bigpond.net.au at Thu, 19 Apr 2007 11:50:25 +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org William Lee Irwin III wrote: > * Andrew Morton wrote: >>> Yes, there are potential compatibility problems. Example: a machine >>> with 100 busy httpd processes and suddenly a big gzip starts up from >>> console or cron. > [...] > > On Thu, Apr 19, 2007 at 08:38:10AM +0200, Ingo Molnar wrote: >> hmmmm. How about the following then: default to nice -10 for all >> (SCHED_NORMAL) kernel threads and all root-owned tasks. Root _is_ >> special: root already has disk space reserved to it, root has special >> memory allocation allowances, etc. I dont see a reason why we couldnt by >> default make all root tasks have nice -10. This would be instantly loved >> by sysadmins i suspect ;-) >> (distros that go the extra mile of making Xorg run under non-root could >> also go another extra one foot to renice that X server to -10.) > > I'd further recommend making priority levels accessible to kernel threads > that are not otherwise accessible to processes, both above and below > user-available priority levels. Basically, if you can get SCHED_RR and > SCHED_FIFO to coexist as "intimate scheduler classes," then a SCHED_KERN > scheduler class can coexist with SCHED_OTHER in like fashion, but with > availability of higher and lower priorities than any userspace process > is allowed, and potentially some differing scheduling semantics. In such > a manner nonessential background processing intended not to ever disturb > userspace can be given priorities appropriate to it (perhaps even con's > SCHED_IDLEPRIO would make sense), and other, urgent processing can be > given priority over userspace altogether. > > I believe root's default priority can be adjusted in userspace as > things now stand somewhere in /etc/ but I'm not sure of the specifics. > Word is somewhere in /etc/security/limits.conf This is sounding very much like System V Release 4 (and descendants) except that they call it SCHED_SYS and also give SCHED_NORMAL tasks that are in system mode dynamic priorities in the SCHED_SYS range (to avoid priority inversion, I believe). Peter -- Peter Williams pwil3058@bigpond.net.au "Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce