Re: INSTDONE instrumentation (patch in progress)

[Chris Wilson <chris@chris-wilson.co.uk>]

On Sun, 31 Oct 2010 02:24:06 +0000, Peter Clifton <pcjc2@cam.ac.uk> wrote:
> Hi guys,
> 
> I thought I'd attach this, as it is now gone 2AM and I doubt I'm going
> to finish it "tonight". I was hoping to elicit some initial review to
> suggest whether the design was sane or not.

Been here, done something similar and ripped it out. What we want to do is
integrate an additional set of sampling with perf. The last time I looked,
it required a few extra lines to perf-core to allow devices to register
their own counters, and then you get the advantage of a reasonable
interface (plus the integration with CPU profiling and timecharts etc).
 
> I'd originally imagined tying the profiling lifetime to the execution /
> completion of individual batch-buffers, but for now I'd like to get it
> partly working like this, and perhaps develop some user-space program to
> view the results and see if they make sense.

You can use the current trace points to get timings for
submit + complete + retire. What's missing here is being able to mark
individual batch buffers for profiling. I think adding a new TIMING_FENCE
ioctl (it could just be a fence ;-) that capture various stats at the
point of submission and completion and then fired off an event (to be read
on the /dev/dri/card0 fd) would be the more flexible solution.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre