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Message-ID: <20100314165720.GC19488@openwall.com>
Date: Sun, 14 Mar 2010 19:57:20 +0300
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: problem with initializing mpirun extended
On Sat, Mar 13, 2010 at 09:47:27AM +0100, Magnum, P.I. wrote:
> The MPI patch seems to make the buffering of logging more noticable.
Why is that? I think it should be taking about as much time (real time,
not CPU time) until the first log flush as it does without the patch.
> If you start a job in background, the check the logs, it may
> very well stop after the "748892 preprocessed word mangling rules" line
> you mention for a very long time. But if you issue a kill -HUP to that
> process, it will flush its log buffer and you'll see it is in fact working.
I think the same would be happening with a single process.
There was a relevant change between 1.7.4 and 1.7.4.2 - LOG_BUFFER_SIZE
was increased from 4 KB to 32 KB. Maybe this confused you into thinking
that MPI had something to do with the change in behavior you've observed.
> I have considered flushing more often but I'm not sure how/when to do it
> without risking introducing performance hits.
Rather than reduce LOG_BUFFER_SIZE, which may hurt performance with a
lot of passwords getting cracked quickly or with a lot of rules and a
small wordlist, you may lower the "Save" setting in john.conf - say,
going from 600 down to 60 seconds won't affect performance significantly.
> The current behaviour is as it comes from mpi10.
I don't see it in the code.
Alexander
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