Re: [Qemu-devel] [PATCH 0/2] Reduce lock contention on TCG hot-path

[Emilio G. Cota]

On Fri, Jul 01, 2016 at 17:16:08 +0100, Alex Bennée wrote:
(snip)
> run 1: ret=0 (PASS), time=4.755824 (1/1)
> run 2: ret=0 (PASS), time=4.756076 (2/2)
> run 3: ret=0 (PASS), time=4.755916 (3/3)
> run 4: ret=0 (PASS), time=4.755853 (4/4)
> run 5: ret=0 (PASS), time=4.755929 (5/5)
> Results summary:
> 0: 5 times (100.00%), avg time 4.755920 (0.000000 deviation)

(snip)
> run 1: ret=0 (PASS), time=9.761559 (1/1)
> run 2: ret=0 (PASS), time=9.511616 (2/2)
> run 3: ret=0 (PASS), time=9.761713 (3/3)
> run 4: ret=0 (PASS), time=10.262504 (4/4)
> run 5: ret=0 (PASS), time=9.762059 (5/5)
> Results summary:
> 0: 5 times (100.00%), avg time 9.811890 (0.060150 deviation)

This is a needless diversion, but I was explaining this stuff today
to a student so couldn't help but notice.

The computed deviations seem overly small. For instance, the corrected sample
standard deviation ( https://en.wikipedia.org/wiki/Standard_deviation )
(which is usually referred to as "standard deviation", or "error")
for the last test should be 0.2742 instead of 0.06.

How are they being computed? I tried to find the source of your script
(in the kvm-unit-tests repo) but couldn't find it.

Thanks,

                Emilio