linux-kernel - Re: Abysmal I/O scheduling with dm-crypt

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Date:	Mon, 19 Sep 2011 14:39:09 -0400
From:	Valdis.Kletnieks@...edu
To:	martin f krafft <madduck@...duck.net>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: Abysmal I/O scheduling with dm-crypt

On Tue, 30 Aug 2011 09:14:07 +0200, martin f krafft said:
> I am using encrypted filesystems (dm-crypt) and the 3.0.0 kernel.
> Underneath might be a RAID1 or a fast SSD. On top is usually LVM
> with a few LVs holding the system.
> 
> Whenever an I/O-intensive task starts, such as:

> the system becomes unusable for several seconds at a time, at least
> once or twice per minute.

Sorry for the late reply - I've seen similar on my laptop.  However, I haven't
dug further into it, because the use case that causes the most pain is backing
up the laptop to a LUKS partition on an external USB drive - and I usually
start that and go to bed so it's not-a-problem.   Also, it only wedges up
those processes that actually try to do disk I/O - which means that all
the terminal windows that are running SSH to various servers don't
usually take a hit and things don't get "unusable" in the sense of "totally
weged and locked up".

But I can at least confirm you're not hallucinating. :)

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