Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Tue, 24 Jul 2012 15:33:19 +0200
From: Frank Dittrich <>
Subject: Re: Confusing --mem-file-size=SIZE description

On 07/24/2012 01:42 PM, magnum wrote:
> On 2012-07-24 12:06, Frank Dittrich wrote:
>> The parameter --mem-file-size is mentioned in the usage output:
>> --mem-file-size=SIZE      size threshold for wordlist preload (default 5 MB)
>> It is also mentioned in doc/OPTIONS.
>> --mem-file-size=SIZE      max. size of wordlist to preload into memory.
>> The unit is not mentioned in the description, so I assume it is in bytes.
>> That means, to change the value from default 5 MB to 100 MB, I would
>> have to use --mem-file-size=100000000. Is that correct?
>> It would be nice to clarify this in doc/OPTIONS.
> Right.
>> The parameter --mem-file-size is also mentioned in doc/README.mpi.
>> Here, the special SIZE values 0, 1, 2 are mentioned.
>> Apparently, for MPI this parameter is mis-used for something completely
>> different. Especially the --mem-file-size=0 meaning in MPI mode is
>> unfortunate, since without MPI, this means: load the complete file into
>> memory. If you have enough memory, this is usually what you want.
> --mem=0 is not different - it's actually where the non-MPI behavior
> stems from. MPI or not, it is a short-cut for saying "buffer the file,
> no matter its size".
>> But for MPI that means, the sequence of password candidates tried will
>> not be optimal for wordlists with candidates sorted by popularity.
> I guess you base that statement on the incorrect assumption that MPI
> will buffer the first 1/n of the wordlist to the first node. This is not
> the case. Each node will buffer every n:th word.

Then I must have misunderstood this;

       --mem-file-size=0   (force split loading, no leapfrog)
       --mem-file-size=1   (force leapfrogging of words)
       --mem-file-size=2   (force leapfrogging of rules)


Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.