[dm-crypt] Larger encryption requests from dm-crypt

Arno Wagner arno at wagner.name
Mon Mar 30 18:52:05 CEST 2015

On Fri, Mar 27, 2015 at 14:40:28 CET, Martin Hicks wrote:
> On Wed, Mar 25, 2015 at 10:54 PM, Arno Wagner <arno at wagner.name> wrote:
> >> (Why it is so slow for 512bytes sectors? Isn't it problem of hw?
> >> The overhead should not be such high...)
> >
> > I am wondering that too. This hardware may have a really,
> > really slow key-setup, far slower than the crypto merits.
> > Would not be the first time that non-crypto people messed
> > something like this up by faulty assumptions on how things
> > are used.
> I'm not sure.  I just assumed it was all the overhead of request queue
> management, servicing interrupts, spinlocks, in addition to the
> hardware setup time. Doing 512byte sectors results in 80000+
> interrupts/sec.

Possibly. Although a key-setup should take longer than 
handling an interrupt and even 80k/sec interrupts should 
not cause much load or slowdown. Of course, it is possible
that this platform is really bad at handling interrupts.

> Anyways, I wasn't fighting for inclusion of this patch, just providing
> it in case anyone else is looking at Talitos' performance.  I will
> take a look at the changes in v4.0 kernel and hopefully adapt this
> patch to the changes.

That is entirely fine. And thanks for posting the info.

> Thanks for your comments,
> mh
> -- 
> Martin Hicks P.Eng.      |         mort at bork.org
> Bork Consulting Inc.     |   +1 (613) 266-2296
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Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
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