Re: [RFC PATCH 00/11] mcount tracing utility

[Frank Ch. Eigler]

Steven Rostedt <rostedt@xxxxxxxxxxx> writes:

> The following patch series brings to vanilla Linux a bit of the RT kernel
> trace facility. This incorporates the "-pg" profiling option of gcc
> that will call the "mcount" function for all functions called in
> the kernel.
> [...]
> [Future:] SystemTap:
> ----------
> One thing that Arnaldo and I discussed last year was using systemtap to
> add hooks into the kernel to start and stop tracing.  

Sure.  The dual of this makes sense too: letting systemtap scripts
hook up to the mcount callback itself, for purposes beyond just
tracing the function calls.

> kprobes is too heavy to do on all funtion calls, but it would be
> perfect to add to non hot paths to start the tracer and stop the
> tracer.

(Note that kprobes are not the only event sources systemtap can use:
markers, timers, procfs control files, and some others.  Any
combination of these can be used in a script to express start/stop
decisions.)


- FChE
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