[Intel-gfx] [PATCH] drm/i915: Add a tracepoint for using a semaphore

[Chris Wilson]

On Mon, Aug 26, 2013 at 04:20:06PM +0300, Ville Syrjälä wrote:
> On Mon, Aug 26, 2013 at 01:46:21PM +0100, Chris Wilson wrote:
> > So that we can find the callers who introduce a ring stall. A single
> > ring stall is not too unwelcome, the right issue becomes when they start
> > to interlock and prevent any concurrent work. That, however, is a little
> > tricker to detect with a mere tracepoint!
> 
> I was staring at the semaphore code a bit recently, and I was wondering
> if it would make sense to do a manual seqno check (against the ring's
> current seqno, not just the last sync_seqno) before we decide to
> add the semaphore into the ring?

If we use the cheap check, yeah. We can also store the cross-sync seqno
as well. Both are going to be unlikely paths though.

Anyway, I'm moving the tracepoint over to the ring rather than the
object for consistency.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre