linux-kernel - Re: Page Allocation Failures/OOM with dm-crypt on software RAID10 (Intel Rapid Storage)

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Message-ID: <d9dbe0328e938eb7544fdb2aa8b5a9c7@mail.ud19.udmedia.de>
Date:	Tue, 12 Jul 2016 13:28:12 +0200
From:	Matthias Dahl <ml_linux-kernel@...ary-island.eu>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	linux-raid@...r.kernel.org, linux-mm@...ck.org,
	dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: Page Allocation Failures/OOM with dm-crypt on software RAID10
 (Intel Rapid Storage)

Hello Michal...

On 2016-07-12 11:50, Michal Hocko wrote:

> This smells like file pages are stuck in the writeback somewhere and 
> the
> anon memory is not reclaimable because you do not have any swap device.

Not having a swap device shouldn't be a problem -- and in this case, it
would cause even more trouble as in disk i/o.

What could cause the file pages to get stuck or stopped from being 
written
to the disk? And more importantly, what is so unique/special about the
Intel Rapid Storage that it happens (seemingly) exclusively with that
and not the the normal Linux s/w raid support?

Also, if the pages are not written to disk, shouldn't something error
out or slow dd down? Obviously dd is capable of copying zeros a lot
faster than they could ever be written to disk -- and still, it works
just fine without dm-crypt in-between. It is only when dm-crypt /is/
involved, that the memory gets filled up and things get out of control.

Thanks,
Matthias

-- 
Dipl.-Inf. (FH) Matthias Dahl | Software Engineer | binary-island.eu
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