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Re: XFS unstable with little memory; OOPS in prune_dcache()

To: linux-xfs@xxxxxxxxxxx
Subject: Re: XFS unstable with little memory; OOPS in prune_dcache()
From: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Date: Tue, 8 Nov 2005 17:38:31 +0100
In-reply-to: <17264.52374.316530.749268@xxxxxxxxxxxxxxxxxx>
Organization: LINBIT
References: <200511081425.06695.philipp.reisner@xxxxxxxxxx> <17264.52374.316530.749268@xxxxxxxxxxxxxxxxxx>
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Am Dienstag, 8. November 2005 17:04 schrieb Peter Grandi:
> philipp.reisner> Hi XFS gurus, I experienced a series of kernel
> philipp.reisner> crashes, that are triggered by:
>
> philipp.reisner> o XFS ( Kernel vanilla 2.6.13.4 )
> philipp.reisner> o uniprocessor (compiled for K7) / no HIGHMEM
> philipp.reisner> o little memory ( 256 MB Ram )
> philipp.reisner> o 200GB XFS filesystem, 138GB used
> philipp.reisner> o   4378907 inodes   ( 4 m)
> philipp.reisner> o  30349548 dentries (30 m)
>
> The crashes are not a big deal, as they don't happen with more
> RAM as you say.
>
> More generally, the rule for most sw, and freee sw too, is ''it
> works for me'', where ''me'' is the developer or the employer of
> the developer.
>

Well, yes and no. Although adding RAM solves the problem for me, and
if my attitude was, I need it to work for my, forget the rest. 
I would not have posted this message.

What I see here, that I triggered a problem that the XFS developers
might not be aware of. Maybe they are happy that someone showed them
an unusual corner case and can fix the issue. Maybe they will simply
ignore me. 

If someone would post a bug report like this to my own project (DRBD)
I am would be happy about it and do my best to fix it as soon as possible.

>
> So if your system is very different from those used by the
> developers, bad luck. Right now most Linux kernel/fs developer
> are employed by large corporates and it is easy to imagine that
> they have >2GB of memory installed.
>
> Also, XFS is designed/targeted to handle very large filesystems
> on very large computers. On the scale of systems for which XFS
> was designed, a 256MB PC is an embedded system.
>

I see it as: The kernel's components might not be efficient with limited
resources, but they must be correct. Especially with memory pressure.

-Phil
-- 
: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :


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