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Message-ID: <7f3840eed2f5f1520b60634b8bb5ffee@smtp.hushmail.com>
Date: Sat, 5 Sep 2020 21:16:40 +0200
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: rar-opencl performance
On 2020-09-04 10:02, Solar Designer wrote:
> On Fri, Sep 04, 2020 at 01:50:02AM +0200, Axymeus wrote:
>> Alright, looks like Windows 10 is not properly reporting GPU usage
>> when running a PowerShell command... Looking at Afterburner I can see
>> that both cRARk and JTR are actually using 100% GPU, but not
>> constantly. There's a brief spike and a brief pause, but a much longer
>> pause between each spike with JTR. CPU usage is about the same. Here
>> is a visual comparison https://i.imgur.com/gIOBKeA.jpg on the left of
>> the graph usage cycle of cRARk and on the right usage cycle of JTR.
>
> OK, so it's possibilities 1 or 2, but not 3. (Of those I listed below.)
>
>> Unfortunately I won't be able to provide the archive being used. And
>> I'm not sure how to produce an equivalent, but I could give it a shot.
>
> magnum, do you have any advice for Axymeus on what parameters of the
> archive to look up and how, and how to replicate those?
Axymeus, please post the result of "unrar vt <archive name>". My guess
is this is a very large "stored" file. I believe cRARk will process
such files fully on GPU if possible, while we will not - as of now. We
could definitely implement that, I just never considered it worthwhile
because it's so uncommon.
Thanks,
magnum
>> On Fri, Sep 4, 2020 at 1:31 AM Solar Designer <solar@...nwall.com> wrote:
>>>
>>> On Fri, Sep 04, 2020 at 01:18:56AM +0200, Axymeus wrote:
>>>> cRARk goes up to 20K p/s on this archive.
>>>
>>> This can mean one of several things:
>>>
>>> 1. cRARk handles the archive smarter, rejecting candidate passwords
>>> earlier. We do have early-reject in many cases, but apparently not
>>> working as effectively in yours. If this is the case, then it's
>>> something magnum (a JtR developer) will want to improve in our
>>> rar-opencl format, I guess. You might want to provide to him a copy of
>>> the archive - or preferably another "equivalent" archive with a known
>>> password and no sensitive content.
>>>
>>> 2. cRARk handles the archive incorrectly, rejecting candidate passwords
>>> early too aggressively, and might produce false negatives (miss the
>>> correct password).
>>>
>>> 3. cRARk implements full archive processing on GPU now - probably not
>>> the case.
>>>
>>> I guess #1 is most likely the case.
>>>
>>> What GPU utilization do you observe when cRARk is running on this
>>> archive? And CPU too? This might give us a hint.
>>>
>>> Alexander
>
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