So I just noticed this 'perf stat --repeat' oddity:
triton:~/tip> perf stat --repeat 3 -a -e instructions taskset 1 perf bench
sched pipe -l 1000000
# Running 'sched/pipe' benchmark:
# Executed 1000000 pipe operations between two processes
Total time: 2.068 [sec]
2.068208 usecs/op
483510 ops/sec
# Running 'sched/pipe' benchmark:
# Executed 1000000 pipe operations between two processes
Total time: 2.097 [sec]
2.097126 usecs/op
476843 ops/sec
# Running 'sched/pipe' benchmark:
# Executed 1000000 pipe operations between two processes
Total time: 2.091 [sec]
2.091716 usecs/op
478076 ops/sec
Performance counter stats for 'system wide' (3 runs):
12,690,156,407 instructions
2.087612423 seconds time elapsed
( +- 0.43% )
the stddev printout of 'instructions' is gone! This defeats the main purpose of
--repeat.
The 'elapsed' time +- stddev/noise display (which is still present) is only
part
of the story.
I'm pretty sure we had the printout for all the measured fields a couple of
months
ago - does any of you know what happened to it?
Thanks,
Ingo
