lkml.org 
[lkml]   [2016]   [Dec]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v7 6/6] siphash: implement HalfSipHash1-3 for hash tables
> 64-bit x86_64:
> [ 0.509409] test_siphash: SipHash2-4 cycles: 4049181
> [ 0.510650] test_siphash: SipHash1-3 cycles: 2512884
> [ 0.512205] test_siphash: HalfSipHash1-3 cycles: 3429920
> [ 0.512904] test_siphash: JenkinsHash cycles: 978267

I'm not sure what these numbers mean. Surely a single siphash2-4
does not take 4+ million cycles?

If you run them in a loop please divide by the iterations.

But generally running small code in a loop is often an unrealistic
benchmark strategy because it hides cache misses, primes
predictors, changes frequencies and changes memory costs,
but also can overload pipelines and oversubscribe
resources.

[see also page 46+ in http://halobates.de/applicative-mental-models.pdf]

So the numbers you get there are at least somewhat
dubious. It would be good to have at least some test which
is not just a tiny micro benchmark to compare before making
conclusions.

-Andi

\
 
 \ /
  Last update: 2016-12-22 01:47    [W:0.121 / U:0.412 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site