Date: Wed, 2 Jul 2008 21:52:01 +1000
From: Bron Gondwana <brong@fastmail.fm>
To: Andi Kleen <andi@firstfloor.org>
Cc: Rob Mueller <robm@fastmail.fm>,
       Michael Kerrisk <mtk.manpages@googlemail.com>,
       Bron Gondwana <brong@fastmail.fm>, Philippe De Muyter <phdm@macqel.be>,
       linux-kernel@vger.kernel.org
Subject: Re: mmap'ed memory in core files ?
Message-ID: <20080702115201.GA12974@brong.net>
References: <20080701132149.GA32510@frolo.macqel> <517f3f820807011116g6ce1b3e1qf166070f7a4c523f@mail.gmail.com> <20080701214423.GA29875@brong.net> <cfd18e0f0807012214o78353faal84a5fa764d3210bf@mail.gmail.com> <3f2201c8dc0d$d1012d60$0b01a8c0@robmhp> <87vdzosfx1.fsf@basil.nowhere.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87vdzosfx1.fsf@basil.nowhere.org>
Organization: brong.net
User-Agent: Mutt/1.5.17+20080114 (2008-01-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1292
Lines: 28

On Wed, Jul 02, 2008 at 01:07:22PM +0200, Andi Kleen wrote:
> "Rob Mueller" <robm@fastmail.fm> writes:
> >
> > It's clearly sparse, but slightly unintuitive that the ulimit doesn't
> > actually limit the filesize, just the size of the data written to the
> > file.
> 
> It's the only sane semantic. Imagine ulimit would limit the address
> range as you seem to be asking for. This means if you set e.g. ulimit
> -c 1G then the kernel would never dump any address (mmap or not) above
> 1GB. Never dumping the process stack for example. Clearly doesn't make
> any sense. And mmap'ed files are not different from any other 
> mappings in this regard.

Hmm.. the IO hit we got with those Cyrus crashes suggested that it was
more than just a small amount of IO being caused.  I didn't check if the
files were sparse or not.

I guess we can probably create a test case that recreates it, even if it's
just running up a dodgy Cyrus instance on the machine that had the crashes
before and deliberately recreating a broken cache file to trigger it.

Bron.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/