Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765396AbXHANe1 (ORCPT ); Wed, 1 Aug 2007 09:34:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762592AbXHANeH (ORCPT ); Wed, 1 Aug 2007 09:34:07 -0400 Received: from mail.suse.de ([195.135.220.2]:45909 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763519AbXHANeF (ORCPT ); Wed, 1 Aug 2007 09:34:05 -0400 Date: Wed, 1 Aug 2007 15:33:58 +0200 From: Andrea Arcangeli To: Dan Merillat Cc: Eric Sandeen , Satyam Sharma , Alan Cox , Matt Mackall , Rene Herman , Ray Lee , Bodo Eggert <7eggert@gmx.de>, Jeremy Fitzhardinge , Jesper Juhl , Linux Kernel Mailing List , William Lee Irwin III , David Chinner , Arjan van de Ven Subject: Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...? Message-ID: <20070801133358.GD6910@v2.random> References: <20070719013955.1bedc423@the-village.bc.nu> <20070719013358.GD29728@v2.random> <20070719013725.GP11115@waste.org> <20070719112436.GG29728@v2.random> <20070719124419.48c3d610@the-village.bc.nu> <46A9ECD5.3050801@sandeen.net> <20070727183807.2d7dbe7b@the-village.bc.nu> <46B003A3.1090507@sandeen.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 871 Lines: 16 On Wed, Aug 01, 2007 at 04:11:23AM -0400, Dan Merillat wrote: > How expensive would it be to allocate two , then use the MMU mark the > second page unwritable? Hardware wise it should be possible, (for Tweaking kernel ptes is prohibitive during clone() because that's kernel memory and it would require a flush tlb all with IPIs that won't scale (IPIs are really the blocker). Basically vmalloc already does what you suggest with the gap page and yet we can't use it for performance reasons. Kernel stack should be readable by any context to allow sysrq+t kind of things, so I doubt it's feasible to do tricks to avoid ipis. - 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/