[dm-crypt] dm-crypt multithreaded yet?

Brian J. Murrell brian at interlinx.bc.ca
Sun Dec 16 22:43:50 CET 2012

On 12-12-16 01:15 PM, Milan Broz wrote:
> No idea why it turned world non-readable, fixed.


> But I am afraid I did not find any real situation where these patches
> really helps

If successive block I/Os from a sequential I/O can all get queued up by
different CPU (cores) I can't imagine why that wouldn't help.

> See also discussion on dm-devel list, I still think generic
> kernel workqueues should be used to provide such parallelization and
> we should not duplicate code in dm-crypt...

Well, definitely, if the parallelization work is duplicating existing
kernel functionality, that needs to be factored out.  But regardless...

> My suggestion is that using AES-NI extension helps much more with
> the current upstream code than anything else (for AES, obviously).

But of course.  I am sure anyone that has a CPU with AES-NI instructions
wouldn't care so much (at all even) about multi-core dm-crypt.  But
unfortunately not everyone has AES-NI capable processors, yet they might
have 4 cores (8 if HT enabled) available, with 3 (7, again if HT is
enabled) all sitting around doing nothing while one is grunting away
with all of the workload.

I wish I could just trade in my laptop for one with AES-NI, but other
than the lack of AES-NI it's far better than what I would get in return
for trading it in.  Kind of like trading in one's Ferrari just because
it doesn't have a leather steering-wheel for a Fiat that does have a
leather steering wheel.  :-/


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