[Mesa-dev] [ANNOUNCE] apitrace 3.0

[José Fonseca]

On Sun, Mar 11, 2012 at 6:59 PM, Dave Airlie <airlied at gmail.com> wrote:
> (resend to include list, I only sent it to Jose by accident).
>
> On Fri, Mar 9, 2012 at 8:22 PM, José Fonseca <jose.r.fonseca at gmail.com> wrote:
>> There are several new features in apitrace that deserve an announcement:
>
> I had an idea for a "feature" the other day but no idea how sane or
> useful it would actually be.
>
> I thought about trying to integrate callgrind and apitrace somehow, so
> we could instrument the CPU usage for a single frame of an
> application.
>
> I think we'd have to run the app under callgrind with instrumentation
> disabled (still slow) then enable it for the single frame.
>
> Just wondering if anyone else thinks its a good idea or know how to
> implement it.

IIUC, you're looking for the ability to profile the app (and not the
GL implementation), for a particular frame, is that right?

There is definitely interest in more profiling on apitrace:
- there have been some patches for GPU/CPU profiling while tracing
(see timing-trace branch) but I believe it is more useful to profile
while retracing
- there have been some patches for GPU profiling while retracing
(timing-retrace branch) but needs some good cleanup
- Ryan Gordon commited patches for CPU profiling while retracing
(commited, glretrace -p option)

Concerning callgrind integration, I personally don't have much trust
in callgrind as profiling tool -- it emulates a CPU instead of
measuring one. It does so using JIT binary translation, which is why
is so slow. Lately i've been using linux perf with good results.
Either way, I don't know if there's any interface to start/stop
measuring or emit some marker from within the app being profiled.

A full opengl wrapper like apitrace it's not necessary -- a LD_PRELOAD
library with just glXSwapBuffers is sufficient --, all that's
necessary is to start/stop/reset the profiler on that call.

I think the hard thing here is really start/stop profiling programmatically.

Jose