Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex

Waiman Long
2014-07-22T19:36:21Z

On 07/21/2014 05:18 PM, Ingo Molnar wrote:
> * Waiman Long<Waiman.Long@hp.com> wrote:
>
>> Testing done on a 4-socket Westmere-EX boxes with 40 cores (HT off)
>> showed the following performance data (average kops/s) with various
>> load factor (number of pause instructions) used in the critical
>> section using an userspace mutex microbenchmark.
>>
>> Threads Load Waiting Futex Spinning Futex %Change
>> ------- ---- ------------- -------------- -------
>> 256 1 6894 8883 +29%
>> 256 10 3656 4912 +34%
>> 256 50 1332 4358 +227%
>> 256 100 792 2753 +248%
>> 10 1 6382 4838 -24%
>> 10 10 3614 4748 +31%
>> 10 50 1319 3900 +196%
>> 10 100 782 2459 +214%
>> 2 1 7905 7194 -9.0%
>> 2 10 4556 4717 +3.5%
>> 2 50 2191 4167 +90%
>> 2 100 1767 2407 +36%
> So the numbers look interesting - but it would be _really_ important
> to provide noise/sttdev figures in a sixth column as well (denoted in
> percentage units, not in benchmark units), so that we know how
> significant a particular speedup (or slowdown) is.
>
> Thanks,
>
> Ingo

The performance can varies quite a bit depending on what other processes
are running at the test execution time. I will include stddev data in
the next iteration of the patch.

-Longman