linux-kernel - Re: x86: 4kstacks default

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Message-ID: <480B4DB4.8070107@sandeen.net>
Date:	Sun, 20 Apr 2008 09:05:40 -0500
From:	Eric Sandeen <sandeen@...deen.net>
To:	Adrian Bunk <bunk@...nel.org>
CC:	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

Adrian Bunk wrote:

> But the more users will get 4k stacks the more testing we have, and the 
> better both existing and new bugs get shaken out.
> 
> And if there were only 4k stacks in the vanilla kernel, and therefore 
> all people on i386 testing -rc kernels would get it, that would give a 
> better chance of finding stack regressions before they get into a 
> stable kernel.

Heck, maybe you should make it 2k by default in all -rc kernels; that
way when people run -final with the 4k it'll be 100% bulletproof, right?
 'cause all those piggy drivers that blow a 2k stack will finally have
to get fixed?  Or leave it at 2k and find a way to share pages for
stacks, think how much memory you could save and how many java threads
you could run!

4K just happens to be the page size; other than that it's really just
some random/magic number picked, and now dictated that if you (and
everyting around you) doesn't fit, you're broken.

That bugs me.

-Eric

(yes, I know there are advantages to only allocating a single page for a
new thread, but from an "all callchains after that must fit in that
space" perspective, it's just a randomly picked number)
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