Date: Fri, 28 Aug 2015 01:21:46 +0200 From: magnum <john.magnum@...hmail.com> To: john-dev@...ts.openwall.com Subject: Re: -dev=... -fork=... wastes GPU memory On 2015-08-25 11:46, magnum wrote: > On 2015-08-25 07:26, Solar Designer wrote: >> 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' >> (...) >> 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 context for all of them. Maybe we can drop the ones we wont use. > I'll have a look at it. I had a look. We take care not to do *anyhing* OpenCL prior to forking. Any such stuff is post-poned. Then right after forking, we enumerate cards and pick one just as if each child was a single process. This made me think that the exact same thing will happen with just a single process, but I just checked and apparently it isn't. Very strange. I need to let this grow for a while. magnum
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