linux-kernel - Re: nbd, nbdkit, loopback mounts and memory management

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Message-ID: <20190217235151.GZ12500@redhat.com>
Date:   Sun, 17 Feb 2019 23:51:51 +0000
From:   "Richard W.M. Jones" <rjones@...hat.com>
To:     Pavel Machek <pavel@....cz>
Cc:     smcdowell@...udbd.io, kernel list <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...l.org>
Subject: Re: nbd, nbdkit, loopback mounts and memory management

On Mon, Feb 18, 2019 at 12:15:14AM +0100, Pavel Machek wrote:
> But Shaun reported it happened somehow often for them, so he might
> have a practical test case... better than my theories :-).

Yes, certainly not saying this isn't a problem.

I think the good news is the fix seems quite easy, ie. to add mlockall
and adjust the OOM killer score, as is done currently in the client:

https://github.com/NetworkBlockDevice/nbd/blob/3969c3f81a11a483f267a55ed6665d260dc9e1d2/nbd-client.c#L867-L885
https://github.com/NetworkBlockDevice/nbd/blob/3969c3f81a11a483f267a55ed6665d260dc9e1d2/nbd-client.c#L1219

For now I have added a note in the TODO file to follow up in case we
get a test case or reports of a problem:

https://github.com/libguestfs/nbdkit/commit/72e0afe2e280d895f68941677fafa559ddc3bb0d

Thanks,

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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