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Message-ID: <20130714184125.GA29194@openwall.com>
Date: Sun, 14 Jul 2013 22:41:25 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: bug: GPU use in CPU-only formats
On Sat, Jul 13, 2013 at 08:16:02PM -0300, Claudio Andr? wrote:
> >This problem is still present, and it manifests itself in an even worse
> >way than I had thought. Not only is there some use of the first GPU
> >during CPU-only runs with an OpenCL-enabled build, but also CPU time is
> >being wasted by some OpenCL-related overhead, which slows down CPU-based
> >cracking (in some of my tests, by more than a factor of 2 - that's when
> >OpenMP is also in use). This is easily reproducible on our new dev box
> >(which I'll create you accounts on shortly), where several ksoftirqd
> >kernel threads appear high in "top" when running a CPU-only format in an
> >OpenCL-enabled build of JtR.
> >
> >Alexander
>
> Is it possible to reproduce this on bull easily?
No, not in my experience.
CPU-only build:
solar@...l:~/j/bleeding-jumbo/run$ ./john -te -form=bcrypt
Will run 8 OpenMP threads
Benchmarking: bcrypt ("$2a$05", 32 iterations) [Blowfish 32/64 X2]... (8xOMP) DONE
Raw: 6624 c/s real, 824 c/s virtual
linux-x86-64-opencl build:
solar@...l:~/j/bleeding-jumbo/run$ ./john -te -form=bcrypt
Will run 8 OpenMP threads
Benchmarking: bcrypt ("$2a$05", 32 iterations) [Blowfish 32/64 X2]... (8xOMP) DONE
Raw: 2700 c/s real, 498 c/s virtual
> Have you tried unstable?
No.
Alexander
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