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Date: Wed, 24 May 2023 00:35:31 +0200
From: magnum <>
Subject: Re: excessive memory usage when running john - 90

On 2023-05-20 19:12, jeff wrote:
> On 5/20/2023 10:04, Solar Designer wrote:
>> On Fri, May 19, 2023 at 05:01:16PM -0700, jeff wrote:
>>> I am quite curious what part of john is using 90 gigabytes of ram, and
>>> why it is using so much memory.
>> We'll need to know more about your invocation of john to tell.  For
>> example, are you running it on a wordlist this large, which could be
>> getting memory-mapped?  JtR was overzealous with memory-mapping of
>> wordlists, which we've since corrected, but I don't know how exactly
>> that would have manifested on Windows.
> I am running it on a very large wordlist, rockyou2021, which is 98 
> gigabytes.
> I suspect it is getting memory mapped.

You should ideally just install a later build, but as an alternative 
quick-fix, find the "WordlistMemoryMapMaxSize" line in john.conf and 
lower it to 1024 (our current default) or something else at your choice. 
The figure is in MB so 1024 means 1 GB).

The idea of memory mapping huge files was that we're talking virtual 
memory here, not real memory - it would only use 98 GB of real memory as 
long as that amount is available. But there where issues with session 
restore (not yet addressed) among other things.


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