Performance probes

[Phil Mayers]

Would a patch adding dtrace/systemtap-compatible source probes be looked 
upon favourably?

I'm fiddling with the debuginfo-based stap stuff to try and get a 
histogram of our ntlm_auth timings, but it strikes me that the 
source-based stuff could be very useful indeed; in particular 
appropriate DTRACE_PROBEx statements could let us time individual 
requests from receive to reply, with minimal performance overhead.

See:

https://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps