* Pekka Enberg <penb...@iki.fi> wrote:
> > %. That was dropped in the recent output change.
>
> Sorry about that. Why do we show them in percentages, btw? Standard
> deviation is usually represented in the same unit as the data to make it
> readable.
So, the problem with output in the same unit is that it's hard to tell
'at a glance' what the real, relative stddev is:
syscall calls min avg max stddev
--------------- -------- -------- -------- -------- ------
sendmsg 2 0.002 0.005 0.008 0.001
recvmsg 2 0.002 0.003 0.005 0.0003
epoll_wait 1 0.000 0.000 0.000 0.000
it's also harder to compare stddevs side by side if they are absolute.
The way we try to solve this in perf stat is to output:
comet:~/tip> perf stat -a --repeat 10 --null usleep 1000
Performance counter stats for 'system wide' (10 runs):
0.001772475 seconds time elapsed
( +- 0.58% )
Oh, btw., would anyone would like to implement a cool new 'perf time'
subcommand, which offers time(1) look-alike output but with better
precision and sttdev output?
comet:~> time usleep 1000
real 0m0.002s
user 0m0.000s
sys 0m0.000s
# Mockup:
comet:~> perf time --repeat 10 usleep 1000
real 0m0.002s [ +- 1.38% ]
user 0m0.000s [ +- 0.53% ]
sys 0m0.000s [ +- 0.43% ]
?
I'd use it instead of 'time' all the time ;-)
Thanks,
Ingo
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