space query

[Jim Keniston]

On Sun, 2012-03-11 at 12:09 -0700, sscheider wrote:
> Howdy!  I am wondering if systemtap probes run in kernel or user space.

For both kernel probes and user-space probes, the probe handlers (i.e.,
what you specify in your stap script) run in kernel space.

However, in probes of user-space code, the probe-handling sequence may
(i.e., if the probed instruction isn't emulated) include single-stepping
a copy of the probed instruction in user space.

> In
> either case, do the probes contribute to the "run" state duration of a given
> PID?

For both kernel and user-space probes, the handler runs in the context
of the process that hit the probepoint.

> If so, which?  I'm using schedtimes.stp.
> Thanks!

Jim Keniston
IBM Linux Technology Center