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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