On 07/21/2014 05:18 PM, Ingo Molnar wrote:
* Waiman Long<Waiman.Long@xxxxxx> 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.
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