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Date: Sun, 24 Jun 2012 23:07:47 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: async key transfers to GPU

myrice -

On Sun, Jun 24, 2012 at 11:02:46PM +0800, myrice wrote:
> I think you mean we do not use multiple streams, we only overlap the
> memcpyH2D with CPU code. So in crypt_all(), I will do the followings
> 1. copy second half of the keys to GPU 2. hash first half of the keys
> 3. hash second half of the keys. When 2 finished, 1 may be already
> done and 3 will start.
> 
> I don't know whether 1 and 2 is overlapped with the same stream. I am
> doing this. Will let you know the result soon.

Yes, I did not suggest to use multiple streams.  I am not familiar with
this, but Lukas was able to have data transfers to GPU overlap with
computation on GPU by interleaving these inside crypt_all().  I am
suggesting an improvement upon this where you'd only need two chunks for
(potentially) full efficiency, whereas Lukas' inside-crypt_all()
approach would need more chunks to get close to full efficiency (but not
reach it).

Please do try this out and post your results.

Thanks,

Alexander

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