linux-kernel - Re: x86: 4kstacks default

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Message-ID: <480B55DF.90502@sandeen.net>
Date:	Sun, 20 Apr 2008 09:40:31 -0500
From:	Eric Sandeen <sandeen@...deen.net>
To:	Willy Tarreau <w@....eu>
CC:	Mark Lord <lkml@....ca>, Andi Kleen <andi@...stfloor.org>,
	Adrian Bunk <bunk@...nel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Shawn Bohrer <shawn.bohrer@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: x86: 4kstacks default

Willy Tarreau wrote:
> On Sun, Apr 20, 2008 at 09:09:37AM -0500, Eric Sandeen wrote:
>> Mark Lord wrote:
>>> Willy Tarreau wrote:
>>>> What would really help would be to have 8k stacks with the lower page
>>>> causing a fault and print a stack trace upon first access. That way,
>>>> the safe setting would still report us useful information without
>>>> putting users into trouble.
>>> ..
>>>
>>> That's the best suggestion from this thread, by far!
>>> Can you produce a patch for 2.6.26 for this?
>>> Or perhaps someone else here, with the right code familiarity, could?
>>>
>>> Some sort of CONFIG option would likely be wanted to
>>> either enable/disable this feature, of course.
>> Changing the default warning threshold is easy, it's just a #define.
> 
> I thought it was checked only at a few places (eg: during irqs). If so,
> maybe it can miss some call chains ?

Ah, ok I skimmed your first suggestion too quickly.  100% coverage
reports on the initial access to the 2nd 4k that way would be nice.
Well, it would be nice if we all really wanted 4k stacks some day... :)

-Eric
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