Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Fri, 4 Nov 2016 15:40:01 +0100
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: John does not fork as many times as I want

On Fri, Nov 04, 2016 at 03:19:32PM +0100, matlink wrote:
> Okay then there is less memory used when cracking hard password
> (allowing using more forks) than when freshly starting to crack the
> hashes?

Sort of, but not exactly.  Rather, there's slower growth in combined
memory needs (which increase through reduction of sharing) by the forked
processes when the successful guesses are not as frequent.

> Is that linked to the "1/3" I can see on the john status? Step
> 3/3 requires less memory when forking than step 1/3?

No, there's no direct relationship to that.  It's just a matter of
getting the weakest passwords out first, at which point you restart and
can run more processes due to them staying more similar to each other
for longer.  If at some point they become dissimilar enough to run out
of memory again, you can interrupt and restore that session (without
losing any work already done).

I also recommend the "--nolog --save-memory=1" options.  (Going higher
than "1" for "--save-memory" will hurt performance, so don't do that.)

Alexander

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