From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161055AbWBAOC0 (ORCPT ); Wed, 1 Feb 2006 09:02:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161058AbWBAOC0 (ORCPT ); Wed, 1 Feb 2006 09:02:26 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:31131 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1161055AbWBAOCZ (ORCPT ); Wed, 1 Feb 2006 09:02:25 -0500 Date: Wed, 1 Feb 2006 15:00:41 +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: <20060201140041.GA5298@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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43E0BBEC.3020209@yahoo.com.au> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.2 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.2 required=5.9 tests=ALL_TRUSTED,AWL autolearn=no SpamAssassin version=3.0.3 -2.8 ALL_TRUSTED Did not pass through any untrusted hosts 0.6 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: > >>So it is not a nice thing to tinker with unless there is good reason. > > > >unbound latencies with hardirqs off are obviously a good reason - but i > >agree that the solution is not good enough, yet. > > Ah, so this is an RT tree thing where the scheduler lock turns off > "hard irqs"? [...] no, this is about the mainline kernel turning off hardirqs for a long time. (i used the hardirqs-off terminology instead of irqs-off to differentiate it from softirqs-off a'ka local_bh_disable(). It's a side-effect of working on the lock validator i guess ;). > [...] As opposed to something like the rwsem lock that only turns off > your "soft irqs" (sorry, I'm not with the terminlogy)? 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 ;) Ingo