[dm-crypt] LUKS/ dm-crypt/ ext4 appears to be single threaded

David Christensen dpchrist at holgerdanske.com
Thu Mar 29 04:56:06 CEST 2012


On 03/28/2012 02:33 PM, Milan Broz wrote:

Thank you for your reply.  :-)


I've been trying to pay more attention, and it appears that the blocking 
is limited to directories (and their subdirectories) where long-lived 
writes are occurring (?).  Am I understanding the issue correctly?  Has 
anyone else seen this?


Is "New Methods in Hard Disk Encryption" still relevant?

     http://clemens.endorphin.org/cryptography


> You forgot to mention kernel version, it changed in various versions.

$ uname -a
Linux p43400e 2.6.32-5-686 #1 SMP Mon Jan 16 16:04:25 UTC 2012 i686 
GNU/Linux

$ sudo cryptsetup --version
cryptsetup 1.1.3

$ cat /etc/debian_version
6.0.4


Are there any tunable parameters, options, alternatives, etc., that I 
can adjust/ change to improve parallelism with what I have?


> For recent kernel 3.x, if multiple processes access the encrypted disk,
> it tries to keep submitted work on cpu which submitted it (so it run in
> parallel).
> There are some patches to change parallel operations to another model
> in dmcrypt, if you want to experiment, see
> http://people.redhat.com/mpatocka/patches/kernel/dm-crypt-paralelizace/current/
> I have several performance tests, and some of these patches perhaps
> appear in 3.5 kernel but it need still more work.

My kernel skills are far too rusty, and I need stability/ finished 
product.  So, I'll have to wait for those patches to get into Debian 
stable (or testing).


David


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