Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758744AbZANFb2 (ORCPT ); Wed, 14 Jan 2009 00:31:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754036AbZANFbS (ORCPT ); Wed, 14 Jan 2009 00:31:18 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:57321 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753224AbZANFbR (ORCPT ); Wed, 14 Jan 2009 00:31:17 -0500 Date: Wed, 14 Jan 2009 06:31:06 +0100 From: Ingo Molnar To: Mike Galbraith Cc: Brian Rogers , linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: [BUG] How to get real-time priority using idle priority Message-ID: <20090114053106.GA10410@elte.hu> References: <4969D0D7.2060401@xyzw.org> <1231736941.6003.7.camel@marge.simson.net> <1231765433.5789.35.camel@marge.simson.net> <20090112131406.GB670@elte.hu> <496BE8F6.1040308@xyzw.org> <1231815523.5899.7.camel@marge.simson.net> <1231910014.610.14.camel@marge.simson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1231910014.610.14.camel@marge.simson.net> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1479 Lines: 36 * Mike Galbraith wrote: > On Tue, 2009-01-13 at 03:58 +0100, Mike Galbraith wrote: > > On Mon, 2009-01-12 at 17:05 -0800, Brian Rogers wrote: > > > > I'll try Mike's "more complete" patch on top of 2.6.29-rc1 and see what > > > that does. > > > > Don't bother. I just tried a SCHED_IDLE make -j8 and had character > > repeats while typing. Must be another spot. > > Hrmph, what an annoying problem. The below works pretty well, but > _still_ has latency problems in some circumstances. > > The more I look at this, the more I think these guys _really_ want to be > a separate class. The problem is the incredible rate of min_vruntime > advancement creating absurdly huge spreads. > > Hm, maybe I could advance min_vruntime at nice 0 when these guys are > running, only advance their vruntime at warp 512, but that seems awfully > hackish. If they were a separate class, they could use the full nice > spectrum instead of being merely mega-nice. A separate class has its own set of problems: starvation, etc. What about increasing the weight of SCHED_IDLE tasks from 1 to 2 or 3? That still makes them mega-nice (which is more than enough), but should make the math a lot less borderline. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/