linux-kernel - Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

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Message-Id: <1184716003.9560.29.camel@segv.aura.of.mankind>
Date:	Wed, 18 Jul 2007 01:46:43 +0200
From:	utz lehmann <lkml123@...4n2c.de>
To:	John Stoffel <john@...ffel.org>
Cc:	Rene Herman <rene.herman@...il.com>, Bodo Eggert <7eggert@....de>,
	Matt Mackall <mpm@...enic.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Jesper Juhl <jesper.juhl@...il.com>,
	Ray Lee <ray-lk@...rabbit.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	William Lee Irwin III <wli@...omorphy.com>
Subject: Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

On Tue, 2007-07-17 at 10:45 -0400, John Stoffel wrote:
> utz> I have to recompile the fedora kernel rpms (fc6, f7) with 8k
> utz> stacks on my i686 server. It's using NFS -> XFS -> DM -> MD
> utz> (raid1) -> IDE disks.  With 4k stacks it crash (hang) within
> utz> minutes after using NFS.  With 8k stacks it's rock solid. No
> utz> crashes within months.
> 
> Does it give any useful information when it does crash?
>  
No, sorry. Nearly always it lock up so hard that even sysrq didn't work
anymore. Most times the console was blanked. If not, there was a line
with "do_irq" or something like that (if i remember correctly).
A few times it continuous oopsing (scrolling like mad).

I think it's just a stack overflow. Knowing that XFS + long IO stack
have problems with 4k stacks. And i have zero crashes with the
recompiled 8k stack kernels. (All kernel are the fedora ones).

Btw: In the past the server runs on slightly different hardware and
without raid1 (NFS -> XFS -> DM -> IDE disk). It runs with 4k stacks. I
had a few crashes, but i blame the hardware for it.

I don't want to make tests with the server. It's my main data storage
and i don't want to risk it.

>  Can you make
> a simple test case using ram disks instead of IDE disks and then
> building upon that?

Sorry, i don't think i can do this. My other computer, which i can use
for tests, is x86_64 based.
And IFAIK the problem on the XFS side has something to do with looking
for freespace on many AGs. So maybe a bigger and filled filesystem is
needed. And 50GB ram disks are out of question.

utz

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