[Intel-gfx] [PATCH] drm/i915: Lazily apply the SNB+ seqno w/a

[Daniel Vetter]

On Thu, Aug 09, 2012 at 12:29:16PM +0200, Daniel Vetter wrote:
> On Thu, Aug 09, 2012 at 10:58:30AM +0100, Chris Wilson wrote:
> > Avoid the forcewake overhead when simply retiring requests, as often the
> > last seen seqno is good enough to satisfy the retirment process and will
> > be promptly re-run in any case. Only ensure that we force the coherent
> > seqno read when we are explicitly waiting upon a completion event to be
> > sure that none go missing, and also for when we are reporting seqno
> > values in case of error or debugging.
> > 
> > This greatly reduces the load for userspace using the busy-ioctl to
> > track active buffers, for instance halving the CPU used by X in pushing
> > the pixels from a software render (flash). The effect will be even more
> > magnified with userptr and so providing a zero-copy upload path in that
> > instance, or in similar instances where X is simply compositing DRI
> > buffers.
> > 
> > v2: Reverse the polarity of the tachyon stream. Daniel suggested that
> > 'force' was too generic for the parameter name and that 'lazy_coherency'
> > better encapsulated the semantics of it being an optimization and its
> > purpose. Also notice that gen6_get_seqno() is only used by gen6/7
> > chipsets and so the test for IS_GEN6 || IS_GEN7 is redundant in that
> > function.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> 
> Yeah, I like the new color.
> 
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> I'll muse over this some more before picking it up, just in case I'll
> notice a place this could blow up ...

Ok, slurped into dinq, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48