linux-kernel - Re: 2.6.25-rc3: 34TB vmalloc total -- overflow in /proc/meminfo?

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Date:	Wed, 5 Mar 2008 23:11:26 +0100 (CET)
From:	Christian Kujau <lists@...dbynature.de>
To:	Hugh Dickins <hugh@...itas.com>
cc:	Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: 2.6.25-rc3: 34TB vmalloc total -- overflow in /proc/meminfo?

On Wed, 5 Mar 2008, Hugh Dickins wrote:
> I don't see what Pavel's issue is with this: it's simply a fact that
> with a 64-bit kernel, we've lots of virtual address space to spare
> for vmalloc.  What would be surprising is for VmallocUsed to get up
> as high as that.

OK, thanks for the clarification.

> Completely different and much more interesting.

Well, if it's "interesting"...here are some more details from the box:

http://nerdbynature.de/bits/2.6.19.2/

> Unlikely.  Offhand I'm not quite sure that's impossible, but it's far
> more likely that we've a kernel bug and vm_committed_space has wrapped
> negative.

Huh. When I first saw this I thought "kernel bug" too, but then read the
documentation to Committed_AS I thought it's just userspace related...

> Ancient as your kernel is, I don't notice anything in the ChangeLogs
> since then to say we've fixed a bug of that kind since 2.6.19.
> Any idea how to reproduce this?

Well, the box is running fine and since it's a production machine I don't 
intend to reboot the box very often. And since it's really an old kernel 
(for lkml discussion, that is) I don't intend to debug this one further. 
I really was only curious if this was userspace related (some app 
overcommitting) or some kernel weirdness.

>  Are you using HugePages at all?

I have:

# CONFIG_HUGETLBFS is not set
# CONFIG_HUGETLB_PAGE is not set

...was this, what you meant?

Thanks,
Christian.
-- 
BOFH excuse #340:

Well fix that in the next (upgrade, update, patch release, service pack).
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