Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161826AbXEDFf3 (ORCPT ); Fri, 4 May 2007 01:35:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161856AbXEDFf3 (ORCPT ); Fri, 4 May 2007 01:35:29 -0400 Received: from nz-out-0506.google.com ([64.233.162.231]:14001 "EHLO nz-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161826AbXEDFf1 (ORCPT ); Fri, 4 May 2007 01:35:27 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:date:to:cc:subject:message-id:mail-followup-to:references:mime-version:content-type:content-disposition:in-reply-to:user-agent:from; b=GrAUIdc0P2sjf4de5CR0YKqitKhBFivr1ov3rSioC1SISQW2xnGlIfNYv2EMdRkrqskeVceDLSXUNOTUa7JW8dMDgVxZDZqbfZ+VGmhkQfGcHn/JRwEwe+cBq3rWssDIiStVHCJdhkkWPE+klRT8gaqgSP613sz5lHnBbKAe1kw= Date: Fri, 4 May 2007 01:35:30 -0400 To: William Lee Irwin III Cc: Andi Kleen , Christoph Hellwig , Alan Cox , David Chinner , Zan Lynx , Adrian Bunk , Linux Kernel Subject: Re: [2/6] add config option to vmalloc stacks (was: Re: [-mm patch] i386: enable 4k stacks by default) Message-ID: <20070504053529.GA3245@nineveh.rivenstone.net> Mail-Followup-To: William Lee Irwin III , Andi Kleen , Christoph Hellwig , Alan Cox , David Chinner , Zan Lynx , Adrian Bunk , Linux Kernel References: <20070428191927.GN3468@stusta.de> <1177795118.7828.6.camel@localhost> <20070430035838.GC77450368@melbourne.sgi.com> <20070430091754.24df88df@the-village.bc.nu> <20070430104806.GA14944@infradead.org> <20070430173819.GC19966@holomorphy.com> <20070430174310.GE19966@holomorphy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070430174310.GE19966@holomorphy.com> User-Agent: Mutt/1.5.13 (2006-08-11) From: jfannin@gmail.com (Joseph Fannin) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1501 Lines: 34 On Mon, Apr 30, 2007 at 10:43:10AM -0700, William Lee Irwin III wrote: > + Allocates the stack physically discontiguously and from high > + memory. Furthermore an unmapped guard page follows the stack. > + This is not for end-users. It's intended to trigger fatal > + system errors under various forms of stack abuse. Why is this not for end-users? Will it not trigger anything useful unless set up properly, or is a big performace hit -- and how, or what? All the kernel debug options are underdocumented this way -- I'd like to have as many of them on as I can without absolutely killing performance, (or rather, *you* would) -- but I can never tell without grovelling all over for the info, which... well, I haven't done it yet, anyway. "End-user" is just insufficently defined for anyone compiling their own kernel. Could you add a bit more text here describing what the effect of physically discontiguous high-memory stacks is? An additional frobnitz dereference on every badda-bing badda-bang, likely to double the time it takes to dance the hokey pokey? *shrug* Some of those debug options probably don't get set very often on kernels that are run for more than to see if it boots. -- Joseph Fannin jfannin@gmail.com - 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/