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Date: Tue, 25 Aug 2015 11:46:04 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: -dev=... -fork=... wastes GPU memory

On 2015-08-25 07:26, Solar Designer wrote:
> magnum,
>
> Running this command on super:
>
> ./john -form=md5crypt-opencl 6.md5crypt.pw -fork=3 -dev=0,1,5 -mask='?l?l?l?l?l?l?l?l'
>
> I get this in nvidia-smi output:
>
> +-----------------------------------------------------------------------------+
> | Processes:                                                       GPU Memory |
> |  GPU       PID  Type  Process name                               Usage      |
> |=============================================================================|
> |    0     17041    C   ./john                                          68MiB |
> |    0     17042    C   ./john                                          68MiB |
> |    0     17043    C   ./john                                         106MiB |
> +-----------------------------------------------------------------------------+
>
> It looks like the two child processes that target other GPUs nevertheless
> consume some memory on this GPU card as well.  Why is that, and can we
> avoid it?
>
> I guess the same happens for AMD GPUs as well, but we don't have such
> nice reporting for them.  Recent nvidia-smi is very nice in this respect.

Interesting. Well, we do enumerate all GPUs and I guess we create some 
kind of contect for all of them. Maybe we can drop the ones we wont use. 
I'll have a look at it.

magnum

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