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

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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.

-Longman
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