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Message-ID: <156de9f8-8882-aac4-6071-c3ef22d4aaee@sremick.net>
Date: Thu, 28 Sep 2017 23:29:10 -0400
From: "Scott I. Remick" <scott@...mick.net>
To: john-users@...ts.openwall.com
Subject: OMP vs. OpenCL performance
Hello! I am taking my first stab playing around with JtR and it's
certainly been enlightening. I have it working (I think) so I don't have
any problems, but instead a question:
My system has an Intel Xeon E3-1276v3 (quad-core 3.6GHz) and an nVidia
GeForce GTX 750. When I ran a pre-built binary (John the Ripper
1.8.0-jumbo-1-5901-gbda8f8e+ OMP [linux-gnu 64-bit AVX2-ac]) and
launched it, I saw it spawn 8 processes (hyperthreading) and was getting
a measly 13-14 p/s on PBKDF2-HMAC-SHA512. But then I compiled a newer
build w/ OpenCL (John the Ripper 1.8.0-jumbo-1-5908-g004c382 OMP
[linux-gnu 64-bit AVX2-ac]), confirmed OpenCL and then forced it with a
suitable --format option. That instance (even running simultaneously as
the OMP instance) is getting currently 760 p/s (and rising, it was 590
when I started) running on just the single GPU. This seems ridiculously
faster...? Is the speed boost really that extreme? I don't even have a
particularly powerful GPU... I figured the 4x CPU 3.6GHz cores
cumulatively would beat it. Or did I mess up something with my CPU/OMP
build?
(This is all on Ubuntu 16.04, if it matters)
This is making me re-think my passively-cooled GPU card! :D For general
usage it's fine (depending on the very-good case cooling), but if I'm
going to start using this as a compute card I might want some sort of
on-card cooling that can respond to GPU temps. 79'C currently, but it's
been rising from the 54'C it was when I started 30 mins ago.
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