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Date: Thu, 8 Sep 2016 12:03:16 +0800
From: Lei Zhang <zhanglei.april@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Intel KNL test machine

2016-09-08 5:14 GMT+08:00 Lukas Odzioba <lukas.odzioba@...il.com>:
> 2016-09-07 15:25 GMT+02:00 Solar Designer <solar@...nwall.com>:
>> Yes, thanks.  Lukas already ran some benchmarks on a similar device, but
>> I think he never published those, in part because the descrypt ones were
>> for AVX2 rather than AVX-512.
>
> I think I can find some spare time this weekend to try to fix code,
> rerun my tests
> and post results, unless Lei wants to do this - which I don't mind :)
>
> Have in mind that AVX512 there is a different set of instructions from
> those on KNC,
> so it's better to use some recent compiler. Also Linux kernel must
> support avx512,
> which you can check via $ cat /proc/cpuinfo | grep -i avx512
> There should be avx512f, avx512pf, avx512cd, avx512er extensions.

The memory model also changed. In KNC native mode, all memory usage
happens in the co-processor's 8GB high-bandwidth memory (I forgot the
exact name...). But KNL is a host CPU; it supports normal DDR and in
the meantime also has its own high-bandwidth memory, which is called
MCDRAM [1].  DDR is the default; special functions are needed to
utilize MCDRAM.

I don't know how much impact memory throughput has on John's
performance. Perhaps John needs to explicitly support KNL's memory
model to fully extract performance from it.


Lei


[1] http://www.hotchips.org/wp-content/uploads/hc_archives/hc27/HC27.25-Tuesday-Epub/HC27.25.70-Processors-Epub/HC27.25.710-Knights-Landing-Sodani-Intel.pdf

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