Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Sat, 19 Nov 2011 23:35:42 -0500
From: Stephen Reese <>
Subject: Re: OpenMP not using all threads

On Sat, Nov 19, 2011 at 11:13 PM, Solar Designer <> wrote:
> On Sat, Nov 19, 2011 at 10:38:30PM -0500, Stephen Reese wrote:
>> Thanks for the quick response. There are 42 hashes and 42 unique salts
>> (13/node). I am going to change this so there are 42 hashes per node
>> and specify the length, (1-6, 7, 8 for All.chr).
>> OpenMP has consistently been around 5000K but I tested another
>> recommendation of yours for running non-OpenMP due to the previously
>> discussed system load woes (GOMP_SPINCOUNT did not help). Four
>> non-OpenMP run at 2000K and a fifth at ~1000K using the same john.pots
>> and password file via multiple sessions--they seem to even out after a
>> bit but a combined 9000K is great! This is what I was looking for.
> It is unclear how you distribute the workload among these 5 processes.
> And why 5?  If you have 8 logical CPUs, then you need 8 processes to use
> the machine optimally.  You'd have 6 of them run on 5 hashes each, and 2
> on 6 hashes each.  As passwords will be getting cracked, the numbers of
> hashes per process will be non-equal anyway, so that's sort of OK.
> Alexander


I confirmed that there are 8 threads (4 cores) in the processor
I asked Linode and their response was there are four cores hence I am
only going to see four entries in /proc/cpuinfo. Maybe they have
hyper-threading disabled (I asked and did not receive a specific

On another note I am glad you responded. I was hoping (under the
impression) that the 5 (seemed to squeeze the most from the system
(prob not)) processes were working together but from what you
described they do not. So each instance needs to reference its own
password file with the hashes that need to be cracked. So I will use 4
processes, each respective process will have 10 unique hash values
associated with it that are not associated with the other 3.

I think I may have to write a script to spawn the 4 processes and the
respective password files as multiple screen sessions are quite
tedious to maintain.

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