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Re: "0-order allocation failed"

To: tls@xxxxxxxxxxxx, linux-xfs@xxxxxxxxxxx
Subject: Re: "0-order allocation failed"
From: Seth Mos <knuffie@xxxxxxxxx>
Date: Sun, 19 Aug 2001 21:15:55 +0200
In-reply-to: <20010819150050.A29326@xxxxxxxxxxxx>
References: <4.3.2.7.2.20010819195213.03383778@xxxxxxxxxxxxx> <20010819134049.A28720@xxxxxxxxxxxx> <4.3.2.7.2.20010819195213.03383778@xxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
At 15:00 19-8-2001 -0400, tls@xxxxxxxxxxxx wrote:
On Sun, Aug 19, 2001 at 07:59:39PM +0200, Seth Mos wrote:
>
> The error message is a general kernel error message which seems to be a
> highmem problem.

I don't see it unless I use XFS.  I don't see it, on this exact same
system, with ext2 or reiserfs.

That's possible, but it is not limited to XFS.

> >I see mention of this bug in a list message from April, but nothing since
> >then. Has it been fixed, or even analyzed? If it's been fixed, is there a
> >simple patch against 1.0.1 or will I need to run the latest from CVS?
>
> I guess that using a kernel later then 2.4.5 may help but this is not
> directly a XFS related error but XFS will help exposing this message
> because it pushes the VM harder.

What does "pushes the VM harder" mean, in this context?

If the filesystem endures high throughput will put more pressure on the memory that is being used. The "0 order allocation" message is trying to tll you that it didn't succeed in allocating memory.

> I don't know if the highmem stuff is significantly better in 2.4.9.
> That is the current CVS tree version which is probably your best bet for
> testing. A 2.4.8 patch is also available on the FTP site.

I noticed a later list message suggesting that a change to XFS in the 2.4.6
timeframe should significantly improve stability on highmem machines; I also
found a message suggesting that there were deadlocks elsewhere in the Linux
kernel on highmem machines until 2.4.7.  So I had high hopes for the 2.4.9
patch.

2.4.9 is not available as a patch on the FTP site yet and you will need to fetch it from CVS.

Unfortunately, though I haven't gotten the machine to hang hard yet, I'm
now running 2.4.9 and a simple cp -R of our CVS repository from one directory
on an XFS filesystem to another produces the "0 order alloc" messages.

These are rather irritating but not related to XFS. If you push ext2 or reiserfs hard enough they will show up as well.

Is this actually believed to be fixed at the moment, or not?  Looks like
not, but I'll leave this running for a few hours and see if I can get an
actual hang.

The message is fairly harmless for now but the box should at least survive this. Stability on highmem is at least better then what it used to be.

Thor

Cheers

--
Seth
Every program has two purposes one for which
it was written and another for which it wasn't
I use the last kind.


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