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Message-ID: <1b21a725e87dcf7fc6e230170b8549fb@smtp.hushmail.com>
Date: Mon, 7 Sep 2015 21:36:37 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: SIMD_PARA_SHA256
On 2015-09-07 11:39, Solar Designer wrote:
> On Mon, Sep 07, 2015 at 09:31:27AM +0200, magnum wrote:
>> On 2015-09-06 21:59, Solar Designer wrote:
>>> We should increase SIMD_PARA_SHA256 from 1 to 2 at least for XOP builds.
>> Perhaps we should do so for SHA-1 too if built without OpenMP (unless
>> that is already the case).
>
> This is not obvious. For fast hashes, we currently disable OpenMP and
> suggest use of --fork, and I expect that --fork will show similar
> behavior to OpenMP in terms of which interleaving factors are optimal.
> Maybe we should test --fork=8 explicitly and decide based on that.
You are right of course. It's a pity you can't "--test --fork" yet. I
only committed the x2 for SHA256 with XOP.
>> Do you have some gcc-4.9 for bull already built that we could try too?
>
> Not already built, but I can build it easily. Why 4.9 and not 5.x?
5.x is also interesting. Ubuntu LTE uses gcc-4.8 and latest Ubuntu uses
gcc-4.9 so those two versions should ideally be tested too. Older
versions than that are of little priority to me.
>> I'll do some new AVX and AVX2 tests.
FWIW I have yet to see anything calling for a change.
> Do you have pre-AVX machines to tune SSE2 and SSE4.1 interleaving on?
> I expect similar tradeoffs there, for Core 2 alikes (no HT) vs. early
> Core i7 (HT).
I could probably find some but again the test matrix quickly grows out
of hands. Some day we should just build tests into ./configure (optional
and along with an instruction to run on unloaded system and so on).
Actually we could just write some instructions instead, for using the
already provided means: Run testpara.pl and then supply good values to
./configure. It's not that inconvenient. Come to think of it,
testpara.pl should end with printing a complete command line for
./configure, ready for copy+paste. That I'll do right now.
magnum
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