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Message-ID: <20100319225700.GA17312@openwall.com>
Date: Sat, 20 Mar 2010 01:57:00 +0300
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: core by core speed
On Wed, Mar 17, 2010 at 11:01:34PM +0100, websiteaccess@...il.com wrote:
> JTR 1.7.5 + 2 latest patch compiled x64 (os X)
>
>
> http://img52.imageshack.us/img52/4053/picturesy.png
>
> As you can see there is a big difference between core speed :( from
> 19% to 98 % time processor)
There could be many different things causing this - the Idle setting
working poorly on your system, those processes doing a lot of file I/O
(waiting for disk), or maybe this is proper reporting of CPU usage for
threads sharing a CPU core (your CPU is quad-core with 2 threads per
core, not 8-core).
When I made Idle = Y the default in JtR 1.7.4+, I asked john-users to
benchmark and see if there was any negative effect of this change, then
report back to me. No one did. :-( (There were some benchmarks of
other properties of JtR. BTW, the Idle setting does not take effect
when running with "--stdout".) I only tested this well on Linux, so I
would not be too surprised if this change had an adverse effect on
another system, especially with SMT (Hyperthreading). I'd appreciate it
if you benchmark Idle = Y vs. Idle = N now - first on a non-MPI build,
then with 4 processes, and finally with 8 processes (6 tests total).
Record the c/s rates and watch the CPU usage by the processes. No need
to run them for long - 1 minute will be enough.
Thanks,
Alexander
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