From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030257AbVKPJTJ (ORCPT ); Wed, 16 Nov 2005 04:19:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030258AbVKPJTI (ORCPT ); Wed, 16 Nov 2005 04:19:08 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:36572 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1030257AbVKPJTH (ORCPT ); Wed, 16 Nov 2005 04:19:07 -0500 Date: Wed, 16 Nov 2005 10:19:13 +0100 From: Ingo Molnar To: Oliver Neukum Cc: Arjan van de Ven , Alex Davis , linux-kernel@vger.kernel.org Subject: Re: [2.6 patch] i386: always use 4k stacks Message-ID: <20051116091913.GA19869@elte.hu> References: <20051116005034.73421.qmail@web50210.mail.yahoo.com> <1132128212.2834.17.camel@laptopd505.fenrus.org> <200511160934.21444.oliver@neukum.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <200511160934.21444.oliver@neukum.org> 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=disabled SpamAssassin version=3.0.4 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 * Oliver Neukum wrote: > Am Mittwoch, 16. November 2005 09:03 schrieb Arjan van de Ven: > > * less CPU cache footprint due to interrupt stacks > >    - interrupt stacks are per cpu now instead of borrowing the per > >      thread stack space; this both has less impact on the caches, and > >      has more cache hits; the per cpu stack will be in cache more than > >      the previously scattered bits and pieces > > * more stack space is available for interrupts compared to 2.4 kernels > >    - in 2.4 kernels only 2Kb was available for interrupt context (to > >      keep 4K available for user context). With complex softirqs such as > >      PPP and firewall rules and nested interrupts this wasn't always > >      enough. Compared to 2.6-with-8Kstacks is a bit harder; there is > >      2Kb extra available there compared to 2.4 and arguably some of that > >      extra is for interrupts. > > This is due to having interrupt stacks. Is there any reason not to > have 8K task stacks and per CPU interrupt stacks? yes, all the other arguments you snipped :) Arjan wrote 4K+4K stacks for Fedora almost 2 years ago, and the patch has a good track record. Here's some more background info about 4K+4K stacks: http://lwn.net/Articles/84583/ http://lwn.net/Articles/150580/ http://lwn.net/Articles/160138/ Ingo