[RFC] filter profiling

[Lennert Buytenhek]

On Tue, Aug 29, 2017 at 07:57:20AM +0200, Vincent Bernat wrote:

> > Feedback appreciated!  (Better ideas also appreciated. :D)
> 
> Using USDT probes? You can attach arbitrary strings to them. I know perf
> supports them (with a recent kernel) but I don't know how
> exactly. However, with systemtap, it's dead easy to see them:
> 
> stap -e 'probe bird.* { print($$vars) }'
> 
> For implementation, see:
>  https://github.com/vincentbernat/lldpd/commit/bdfe419389075af3cdfeadc78008a157afc2d5d7
>  https://github.com/vincentbernat/lldpd/commit/140e34f057462d5ff7818ab4af368f055eaad4e3

As far as I can see, these are tracepoints, but they wouldn't let me do
profiling?  What I need is profiling, as I want to know what's consuming
the most CPU, so I want to be able to fire an event N times per second
to tell me what bird is doing right at that specific moment, and listing
or counting tracepoint invocations won't necessarily tell me what's using
up the most CPU.