Date: Wed, 27 Jun 2012 07:46:40 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: mschap-v2 conversion On Wed, Jun 27, 2012 at 01:44:28AM +0200, magnum wrote: > On 2012-06-26 15:02, Solar Designer wrote: > > On Tue, Jun 26, 2012 at 10:06:47AM +0200, magnum wrote: > >> Solar may respond much better when he gets some more time. > > > > I'm sorry, but my opinion is that tuning OpenMP performance with the > > current early/experimental bitslicing implementation for this format is > > premature. > > This is my fault, No problem. > I just noticed she broke OMP and she went off fixing > it. Anyway, even if it's not time to really *tune* it, it should > definitely not be slower than running one core. Running slower than on one core may happen during development. > > Notice that the speedup from bitslicing without OpenMP is quite low, > > compared to what we're seeing for purely DES formats (much higher > > speedup there). I guess this might be because of the uses of MD4 and > > the conversions to/from bitslice representation, but that does not > > explain the low speed for the "many salts" case (the uses of MD4 are in > > key setup only). We need to seriously look into this and see what can > > be done about it. > > I presume Deepika is not really interested in this particular format but > in bit-slicing, so using SSE2 for MD4 might be out of scope. I could add > SSE2 for MD4 at some point if it helps. I just need to understand the > context. If we always have 32 or 64 (or 128) keys at a time, it should > be a walk in the park. Right. > I just know the basic theory of BS. Deepika, what is the expected > speedup from just BS (no OMP) if this had been a straight format with no > MD4 and stuff involved? If we run 64-bit, we do 64 items at a time, > right? But it's not 64x faster of course. How much faster, in general, > should it be? Sorry for commenting on a question addressed to Deepika rather than to me, but I'd expect it to be "a few times" faster even on a 32-bit build for the "many salts" case. BTW, it looks like not only the MD4 stuff, but also DES key setup may be done out of the per-salt loop. Alexander
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