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Message-ID: <a38d646288473fc3b4e113c1e8346437@smtp.hushmail.com>
Date: Sun, 23 Aug 2015 23:10:24 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: interleaving on GPUs
On 2015-08-23 23:05, magnum wrote:
> On 2015-08-23 07:08, Solar Designer wrote:
>> I just read this about NVIDIA's Kepler (such as the old GTX TITAN that
>> we have in super):
>>
>> http://docs.nvidia.com/cuda/kepler-tuning-guide/index.html#device-utilization-and-occupancy
>>
>>
>> "Also note that Kepler GPUs can utilize ILP in place of
>> thread/warp-level parallelism (TLP) more readily than Fermi GPUs can.
>> Furthermore, some degree of ILP in conjunction with TLP is required by
>> Kepler GPUs in order to approach peak single-precision performance,
>> since SMX's warp scheduler issues one or two independent instructions
>> from each of four warps per clock. ILP can be increased by means of, for
>> example, processing several data items concurrently per thread or
>> unrolling loops in the device code, though note that either of these
>> approaches may also increase register pressure."
>>
>> Note that they explicitly mention "processing several data items
>> concurrently per thread". So it appears that when targeting Kepler, up
>> to 2x interleaving at OpenCL kernel source level could make sense.
>
> Shouldn't simply using vectorized code (eg. using uint2) result in just
> the interleaving we want (on nvidia)? I tested this with some of our
> formats that can optionally run vectorized but they don't seem to gain
> from --force-vector=2.
BTW here's a list of such formats:
$ git grep -l v_width *fmt*c
opencl_encfs_fmt_plug.c
opencl_krb5pa-sha1_fmt_plug.c
opencl_ntlmv2_fmt_plug.c
opencl_office2007_fmt_plug.c
opencl_office2010_fmt_plug.c
opencl_office2013_fmt_plug.c
opencl_pbkdf2_hmac_md4_fmt_plug.c
opencl_pbkdf2_hmac_md5_fmt_plug.c
opencl_pbkdf2_hmac_sha1_fmt_plug.c
opencl_rakp_fmt_plug.c
opencl_sha1crypt_fmt_plug.c
opencl_wpapsk_fmt_plug.c
I tried PBKDF2-HMAC MD4, MD5 and SHA-1 but they all lost some performance.
magnum
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