[Intel-gfx] [PATCH] drm/i915: add turbo boost trace point

[Jesse Barnes]

On Wed, 19 Nov 2014 17:19:23 +0100
Daniel Vetter <daniel at ffwll.ch> wrote:

> On Wed, Nov 19, 2014 at 07:39:17AM -0800, Jesse Barnes wrote:
> > On Wed, 19 Nov 2014 15:00:04 +0100
> > Daniel Vetter <daniel at ffwll.ch> wrote:
> > 
> > > On Tue, Nov 18, 2014 at 01:12:29PM -0800, Jesse Barnes wrote:
> > > > Might be helpful for debugging places where userspace ends up boosting
> > > > or waiting where it doesn't intend to.
> > > 
> > > Might be feels a bit weak justification for a new tracepoint imo. Please
> > > drum up more support.
> > 
> > I put it together for some media playback debugging we're doing on
> > Chrome, where I suspect we're boosting when we don't want to (possibly
> > due to userspace waits).
> 
> Hm, I've discussed this exact topic many moons ago with vpg folks and
> they've said that the boosting done for media workloads on the idle->busy
> transition annoys them. Iirc the plan we've hashed out was to add an
> execbuf flag to prevent the execbuf boosting.
> 
> We've also discussed the wait boosting but that's imo just a bug in libva
> ;-) And for debugging pointless waits we already have good tracepoints
> imo.

We have tracing for waits, but my expectation was that we may end up
growing or adding new boost points elsewhere, so having an explicit
trace would make sense anyway.

But we've already typed many more lines about this than the patch
itself contains, so feel free to drop/ignore.  It's easy enough to add
on an ad-hoc basis.

-- 
Jesse Barnes, Intel Open Source Technology Center