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Re: LUKS/ dm-crypt/ ext4 appears to be single threaded



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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