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Date: Fri, 4 Sep 2020 00:27:55 +0200
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: rar-opencl performance

On Thu, Sep 03, 2020 at 11:47:50PM +0200, Axymeus wrote:
> However while john is now running, I'm not entirely convinced it's
> making any use of the GPU. I'm not seeing any GPU utilization from
> john (really 0%), and performance is only slightly better than running
> with the CPU (~800 p/s versus 250 p/s, using an i7-8700, a quick test
> with cRARk tells me my GPU should be able to reach ~18,000 p/s. Of
> course we're looking at different softwares but still). John also uses
> the same number of OpenMP threads (12) on both runs

The 0% utilization is weird, and 800 p/s is low.  How long have you been
running it for?  Can you show the status line?  My guess is it's still
in "single crack" mode (pass "1/3") where it isn't giving the GPU enough
work yet.  If the RAR file's name isn't a good hint for use in candidate
passwords, you may skip that and use other cracking modes right away
(you'll need to request those explicitly).

As to comparison with cRARk, as I recall it benchmarks for password
length 5, and we do the same in our "--test" for consistency, but
performance is lower for higher lengths (with any tool):

[solar@...er run]$ ./john -test -form=rar-opencl -dev=5
Will run 32 OpenMP threads
Device 5: GeForce GTX TITAN X
Benchmarking: rar-opencl, RAR3 (length 5) [SHA1 OpenCL AES]... (32xOMP) LWS=32 GWS=6144 (192 blocks) DONE
Raw:	31879 c/s real, 30306 c/s virtual, Dev#5 util: 100%

[solar@...er run]$ ./john -test -form=rar-opencl -dev=5 -mask='?a?a?a?a?a?a'
Will run 32 OpenMP threads
Device 5: GeForce GTX TITAN X
Benchmarking: rar-opencl, RAR3 (length 6) [SHA1 OpenCL AES]... (32xOMP) LWS=32 GWS=6144 (192 blocks) DONE
Raw:	29257 c/s real, 27551 c/s virtual, Dev#5 util: 100%

[solar@...er run]$ ./john -test -form=rar-opencl -dev=5 -mask='?a?a?a?a?a?a?a'
Will run 32 OpenMP threads
Device 5: GeForce GTX TITAN X
Benchmarking: rar-opencl, RAR3 (length 7) [SHA1 OpenCL AES]... (32xOMP) LWS=32 GWS=24576 (768 blocks) DONE
Raw:	27306 c/s real, 26520 c/s virtual, Dev#5 util: 100%

[solar@...er run]$ ./john -test -form=rar-opencl -dev=5 -mask='?a?a?a?a?a?a?a?a'
Will run 32 OpenMP threads
Device 5: GeForce GTX TITAN X
Benchmarking: rar-opencl, RAR3 (length 8) [SHA1 OpenCL AES]... (32xOMP) LWS=32 GWS=6144 (192 blocks) DONE
Raw:	25134 c/s real, 24041 c/s virtual, Dev#5 util: 100%

I don't suggest you actually use mask mode when cracking, although you
may (good idea if you recall part of the password) - rather, this is how
we specify a length for the benchmarks above.

Alexander

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