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Date: Tue, 25 Aug 2015 08:26:54 +0300
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: -dev=... -fork=... wastes GPU memory

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.

Alexander

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