[Question] Hooks for scheduler tracing (CFS)

["Remy Bohmer" <l.pinguin@gmail.com>]

Hello,

I am looking for some tool/kernel machanism that enables me to track
every schedule change on the CFS scheduler of the RT-kernel for some
period of time.
Thus a tool that gives me an overview after some time which task got
"scheduled in/out" at "which timestamp" and at "which CPU". ( I need
the raw data)

In a far past (on Montavista kernels) I used LTT for this to log for
some time with only the SCHED_CHANGE filter and text output. But, I
cannot find any LTT(ng) support for any RT-kernel, and support for the
new CFS (like in 2.6.22.1-rt4) is even harder.

So I was wondering if anybody knows some tool/kernel mechanism which
can do this?
If not, I will build a kernel extension for it myself (new extension
to 'latency_trace' ?)
In that case can anybody with in depth CFS scheduler knowledge please
point me which hooks are safe to use for this?

I need it to get a detailed insight in my RT-system with its RT and
non-RT applications.
Thus to know when a certain task gets scheduled (and to calculate its
per thread min/max/avg latencies), which task preempts another task,
and to get a complete overview of what the RT system (and scheduler)
is doing during time etc.


Kind Regards,

Remy Böhmer