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Message-ID: <20130713203356.GA26724@openwall.com>
Date: Sun, 14 Jul 2013 00:33:56 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: bug: GPU use in CPU-only formats

magnum, Claudio -

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

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