[Intel-gfx] [PATCH 3/3] drm/i915: add fences to the request struct

[Daniel Vetter]

On Thu, Dec 04, 2014 at 09:13:21AM +0000, Chris Wilson wrote:
> On Wed, Dec 03, 2014 at 11:49:07AM -0800, Jesse Barnes wrote:
> > This simplifies the sync code quite a bit.  I don't think we'll be able
> > to get away with using the core fence code's seqno support, since we'll
> > be moving away from simple seqno comparisions with the scheduler and
> > preemption, but the additional code is pretty minimal anyway, and lets
> > us add additional debugging as needed, so it's probably fine to keep
> > either way.
> > 
> > We still need to add support for other rings here; we ought to be able
> > to do that with the timeline field of the ioctl (which will include
> > other "rings" like the display flip queue for example).
> 
> I am ambivalent about this. I don't think migrating i915_request over to
> use the heavyweight fence primitives is a good idea, so see little value
> in embedding the struct fence inside i915_request vs a small bookkeeping
> struct referencing i915_request.

Which part of struct fence is too heavyweight? And I guess we could always
add a slab or some cache if the allocation overhead is too much. I really
like this conceptually so if there's a concern with overhead I want solid
data for it.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch