Re: Using sched_clock for mmio-trace

Jeff Muizelaar
2007-02-16T19:54:27Z

On Fri, Feb 16, 2007 at 10:44:15AM -0800, Randy Dunlap wrote:
> On Fri, 16 Feb 2007 13:30:14 -0500 Jeff Muizelaar wrote:
>
> > On Fri, Feb 16, 2007 at 11:30:56AM -0500, Frank Ch. Eigler wrote:
> > > Jeff Muizelaar <jeff@infidigm.net> writes:
> > >
> > > > I've built a tool with the goal of logging mmio writes and reads by
> > > > device drivers. See http://nouveau.freedesktop.org/wiki/MmioTrace.
> > >
> > > FWIW, this is exactly a type of add-on trace patch that could be
> > > mooted by adoption of the ltt/systemtap "marker" facility. With it,
> > > you would not need so much code (e.g. no new user-space tools at all,
> > > reuse of common tracing buffer logic, permanently placed hooks) and
> > > would probably get more utility.
> >
> > Is there more information on this "marker" facility? e.g. what is a
> > marker? Are they just like tracepoints?
>
> On lkml for the past few days/months.
> Look for "Linux Kernel Markers" in the subject line.
>
> Mathieu, do you have a web site for LK Markers?
>

Yeah, so if I understand correctly, markers are basically compile time locations
that you can attach function calls to at run time, right?. If so, I
don't think they are of much use to me.

What I am doing is page-faulting on every read or write to an mmio
region, decoding the faulting instruction and passing the decoded
information up to userspace through relayfs.

-Jeff