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Date: Fri, 4 May 2007 01:35:30 -0400 From: jfannin@...il.com (Joseph Fannin) To: William Lee Irwin III <wli@...omorphy.com> Cc: Andi Kleen <andi@...stfloor.org>, Christoph Hellwig <hch@...radead.org>, Alan Cox <alan@...rguk.ukuu.org.uk>, David Chinner <dgc@....com>, Zan Lynx <zlynx@....org>, Adrian Bunk <bunk@...sta.de>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: [2/6] add config option to vmalloc stacks (was: Re: [-mm patch] i386: enable 4k stacks by default) 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@...il.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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