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Date: Tue, 4 Sep 2012 07:47:05 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: memory usage (was: [john-users] JTR against 135 millions MD5 hashes)

Jim -

On Mon, Sep 03, 2012 at 11:12:18PM -0400, jfoug@....net wrote:
> On Mon, Sep 3, 2012 at 8:49 PM, Solar Designer wrote:
> >I did not realize that there were wasteful allocations in prepare() 
> >and valid().  Weren't they temporary?
> 
> They were done using alloc_memory_tiny.  Now, I simply use static 
> buffers.  When raw hashes were being used, and a few other cases, there 
> could be one or more of these type allocations, which are very similar 
> to memory leaks, when done on temp transient data.

Did you include fixes for this in the fixes branch?  If not yet, can you
do that?  I guess those changes are non-invasive.

> >Another potential source of memory usage reduction are the alignments.
> >For raw MD5 hashes, a 4-byte alignment should suffice (they're 4x4
> >bytes), yet we were using 8-byte alignment on 64-bit builds.
> 
> Very good point. I had not even thought of things like these new 
> alignment requirements.  I really think for most formats, 4 is the 
> correct alignment, due to dereference of an arch_word_32 in some of the 
> lookup functions.
> 
> I do not have time to fully address all of the issues brought up in your 
> reply, but will try to look more in depth at this tomorrow afternoon.

I think that for now our priority should be specifying proper alignments
for each format's binary and salt (in bleeding).

Thanks,

Alexander

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