Re: resolving probe point context_switch

[fche@redhat.com (Frank Ch. Eigler)]

"Jason Yeh" <jason.yeh@amd.com> writes:

> [...]  I have been trying to get Systemtap to place probe in the
> scheduler and hoping to experiment using Systemtap to emulate
> certain behavior of Perfmon2 similar to what Frank mentioned in the
> email titled "Model-Specific Register".

Thanks for giving that a try!

> [...]
> while: resolving probe point kernel.inline("context_switch")
> while: resolving probe point kernel.inline("finish_task_switch")
> while: resolving probe point kernel.inline("pull_task")
> while: resolving probe point kernel.inline("idle_balance")

We have some known weaknesses probing inline functions, which we may
be able to improve significantly.  In the mean time, something coarser
might have to do:

      probe kernel.statement("schedule") { /* leaving tid() on cpu() */ }
      probe kernel.function("schedule").return { /* resuming tid() on cpu() */ }

FWIW, the scheduler is one of the spots that would benefit most from
static instrumentation markers.


- FChE