static user probe performance

[Frank Ch. Eigler]

Stan Cox <scox@redhat.com> writes:

> [...]
> not run with stap
> [...]
> elapsed time
>       volatile no semaphore 38.18
>       no volatile no semaphore 48.02
>       volatile semaphore 51.66
>       no volatile semaphore 60.23

I don't understand these numbers.  The "no volatile" version is
consistently slower than "volatile".  How can that be?


> run with stap
> [...]
> elapsed time
>       volatile semaphore 1858.71
>       no volatile no semaphore 1865.68
>       volatile no semaphore 1873.07
>       no volatile semaphore 1878.09

So for this particular microbenchmark, systemtap probing imposes a 30x
slowdown, yikes.  How many probe hits does this represent?

- FChE