[dm-crypt] Re : Re : Poor performances with nfs and Kernel 3.x

Arno Wagner arno at wagner.name
Thu Feb 9 13:04:37 CET 2012


On Thu, Feb 09, 2012 at 11:19:30AM +0100, Milan Broz wrote:
> On 02/09/2012 08:37 AM, Arno Wagner wrote:
> >On Wed, Feb 08, 2012 at 05:55:21PM +0000, Mickael wrote:
> >>Here are more tests focusing the CPU load with htop snapshot:
> >>
> >>with Kernel 3.x, nfsd threads are using more CPU !?
> >
> >This is what I suspected. You setup is already slightly
> >CPU-limited when reading/writing encrypted partitions.
> >Any additional CPU needed by NFS is then directly deduced
> >from CPU available for encryption.
> 
> Not sure if it help, but it would be interesting if you can try
> to use patch from this thread
> http://article.gmane.org/gmane.linux.kernel/1245748
> 
> (it can be completely unrelated though, I have no time to test
> it now myself)
> 
> BTW I will add possibility to use null cipher to cryptsetup,
> just to test exactly these situations (null cipher eliminates all
> crypto operations), 


That is a really good idea!

Arno



> for now, you can try it with dmsetup and
> measure preformance (this should uncover if encryption is
> the problem or there is some timing problem):
> 
> (Replace DEV with your disk, note key is "-" - means empty)
> 
> dmsetup create x --table "0 $(blockdev --getsz DEV) crypt cipher_null-ecb-null - 0 DEV 0"
> 
> Milan
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-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
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----
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are stupid, and those with any imagination and understanding are filled 
with doubt and indecision. -- Bertrand Russell 


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