linux-kernel - Re: random: Benchamrking fast

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	14 Jun 2014 01:25:27 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	linux@...izon.com, tytso@....edu
Cc:	hpa@...ux.intel.com, linux-kernel@...r.kernel.org,
	mingo@...nel.org, price@....edu
Subject: Re: random: Benchamrking fast_mix2

> At least for Intel, between its branch predictor and speculative
> execution engine, it doesn't make a difference.  

*Sigh*.  We need live measurement.  My testing (in your test
harness!) showed a noticeable (~10%) speedup.

> When I did a quick comparison of your 64-bit fast_mix2 variant, it's
> much slower than either the 32-bit fast_mix2, or the original fast_mix
> alrogithm.

That is f***ing *bizarre*.  For me, it's *significantly* faster.
You *are* compiling -m64, right?  Because I agree with you it'd
be stupid to try to use it on 32-bit machines.

Forcing max-speed CPU:
# ./perftest ./ted64
fast_mix: 419   fast_mix2: 419  fast_mix4: 318
fast_mix: 386   fast_mix2: 419  fast_mix4: 112
fast_mix: 419   fast_mix2: 510  fast_mix4: 328
fast_mix: 420   fast_mix2: 510  fast_mix4: 306
fast_mix: 420   fast_mix2: 510  fast_mix4: 317
fast_mix: 419   fast_mix2: 510  fast_mix4: 318
fast_mix: 362   fast_mix2: 510  fast_mix4: 317
fast_mix: 420   fast_mix2: 510  fast_mix4: 306
fast_mix: 419   fast_mix2: 499  fast_mix4: 318
fast_mix: 420   fast_mix2: 510  fast_mix4: 328

And not:
$ ./ted64
fast_mix: 328   fast_mix2: 430  fast_mix4: 272
fast_mix: 442   fast_mix2: 442  fast_mix4: 272
fast_mix: 442   fast_mix2: 430  fast_mix4: 272
fast_mix: 329   fast_mix2: 442  fast_mix4: 272
fast_mix: 329   fast_mix2: 430  fast_mix4: 272
fast_mix: 328   fast_mix2: 442  fast_mix4: 272
fast_mix: 329   fast_mix2: 431  fast_mix4: 272
fast_mix: 328   fast_mix2: 442  fast_mix4: 272
fast_mix: 328   fast_mix2: 431  fast_mix4: 272
fast_mix: 329   fast_mix2: 442  fast_mix4: 272

And on a Phenom:
$ /tmp/ted64
fast_mix: 250   fast_mix2: 174  fast_mix4: 109
fast_mix: 258   fast_mix2: 170  fast_mix4: 114
fast_mix: 371   fast_mix2: 285  fast_mix4: 109
fast_mix: 516   fast_mix2: 156  fast_mix4: 90
fast_mix: 140   fast_mix2: 184  fast_mix4: 170
fast_mix: 406   fast_mix2: 146  fast_mix4: 88
fast_mix: 185   fast_mix2: 114  fast_mix4: 94
fast_mix: 161   fast_mix2: 116  fast_mix4: 98
fast_mix: 152   fast_mix2: 104  fast_mix4: 94
fast_mix: 352   fast_mix2: 140  fast_mix4: 79

> So given that 32-bit processors tend to be slower, I'm pretty sure
> if we want to add a 64-bit optimization, we'll have to conditionalize
> it on BITS_PER_LONG == 64 and include both the original code and the
> 64-bit optimized code.

Sorry I neglected to say so earlier; that has *always* been my intention.
The 32-bit version is primary; the 64-bit version is a conditional
optimization.

If I can make it faster *and* have more avalanche (and less register
pressure, too), it seems worth the hassle of having two versions.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/