From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161051AbWBAOYQ (ORCPT ); Wed, 1 Feb 2006 09:24:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161062AbWBAOYQ (ORCPT ); Wed, 1 Feb 2006 09:24:16 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:58285 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S1161051AbWBAOYP (ORCPT ); Wed, 1 Feb 2006 09:24:15 -0500 Date: Wed, 1 Feb 2006 15:22:49 +0100 From: Ingo Molnar To: Nick Piggin Cc: Steven Rostedt , Peter Williams , Thomas Gleixner , Andrew Morton , LKML Subject: Re: [PATCH] Avoid moving tasks when a schedule can be made. Message-ID: <20060201142249.GB6277@elte.hu> References: <1138736609.7088.35.camel@localhost.localdomain> <43E02CC2.3080805@bigpond.net.au> <1138797874.7088.44.camel@localhost.localdomain> <43E0B24E.8080508@yahoo.com.au> <43E0B342.6090700@yahoo.com.au> <20060201132054.GA31156@elte.hu> <43E0BBEC.3020209@yahoo.com.au> <20060201140041.GA5298@elte.hu> <43E0C127.8060401@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43E0C127.8060401@yahoo.com.au> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=no SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Nick Piggin wrote: > >rwsems/rwlocks are not an issue in -rt because they have different > >semantics there - and thus readers cannot amass. I do think rwsems and > >rwlocks have pretty nasty characteristics [non-latency ones] for the > >mainline kernel's use too, but that's not being argued here ;) > > But all I'm saying is that while there are equivalent magnitudes of > interrupts off regions in mainline, there is little point introducing > a hack like this to "solve" one of them. nobody is arguing to have this hack included. Hacks are to be introduced into the scheduler only over my cold dead body ;-) Steve only sent this as an RFC thing, to raise the issue. > If anyone is running hackbench 20 on their sound mixer, then they > deserve to have overruns. just to give you an idea of what we have achieved with the -rt kernel so far: my regular -rt stress-test setup has a "hackbench 50" in its "deadly mix of SCHED_OTHER workloads", in addition to 40 parallel runs of LTP runalltests.sh, with flood pinging and other networking and IO stresstests, combined with a task that allocates and dirties a 1.5GB buffer in an infinite loop while there's only 1GB of RAM - and still during many hours of running this stress-test (which produces a load average of 200-500) the -rt kernel runs SCHED_FIFO tasks in 20 usecs, worst-case. Ingo