IPI Benchmark Data?

Matthew Dillon dillon at backplane.com
Wed Aug 3 09:29:24 PDT 2016


I have some saved output from ./ipitest script runs that I've run on
various cpus:

http://apollo.backplane.com/DFlyMisc/ipitest01.txt

http://apollo.backplane.com/DFlyMisc/ipitest02.txt

http://apollo.backplane.com/DFlyMisc/ipitest03.txt

http://apollo.backplane.com/DFlyMisc/ipitest04.txt

http://apollo.backplane.com/DFlyMisc/ipitest05.txt

The numbers are in nanoseconds, so e.g. '2900' would be 2.9uS. '29000'
would be 29uS.  The originating cpu is #0.  As an example, taking
ipitest05.txt, due to the topological layout cpu #16 is the co-thread for
 cpu #0 and one can see it in the numbers (since cpu #0 is initiating the
test, it's generally not running in a low-power mode regardless of the C
state we use).

The results generally follow expectations.  A cpu sitting in a deep C state
can take over 30uS to respond.  Minimum IPI latency is usually in the 1-2uS
range.

​-Matt
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