[Intel-gfx] [PATCH 17/70] drm/i915: Optimistically spin for the request completion

[Daniel Vetter]

On Wed, Apr 08, 2015 at 01:43:47PM +0000, Rantala, Valtteri wrote:
> Hi, 
> 
> 
> > -----Original Message-----
> > From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
> > Sent: Wednesday, April 08, 2015 2:40 PM
> > To: Chris Wilson
> > Cc: intel-gfx at lists.freedesktop.org; Daniel Vetter; Tvrtko Ursulin; Tamminen,
> > Eero T; Rantala, Valtteri
> > Subject: Re: [PATCH 17/70] drm/i915: Optimistically spin for the request
> > completion
> > 
> > On Tue, Apr 07, 2015 at 04:20:41PM +0100, Chris Wilson wrote:
> > > This provides a nice boost to mesa in swap bound scenarios (as mesa
> > > throttles itself to the previous frame and given the scenario that
> > > will complete shortly). It will also provide a good boost to systems
> > > running with semaphores disabled and so frequently waiting on the GPU
> > > as it switches rings. In the most favourable of microbenchmarks, this
> > > can increase performance by around 15% - though in practice
> > > improvements will be marginal and rarely noticeable.
> > >
> > > v2: Account for user timeouts
> > > v3: Limit the spinning to a single jiffie (~1us) at most. On an
> > > otherwise idle system, there is no scheduler contention and so without
> > > a limit we would spin until the GPU is ready.
> > > v4: Drop forcewake - the lazy coherent access doesn't require it, and
> > > we have no reason to believe that the forcewake itself improves seqno
> > > coherency - it only adds delay.
> > >
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > > Cc: Eero Tamminen <eero.t.tamminen at intel.com>
> > > Cc: "Rantala, Valtteri" <valtteri.rantala at intel.com>
> > 
> > Eero/Valtterri, do you have perf data for this one?
> > 
> [Rantala, Valtteri] 
> I have issues with applying this patch to latest night, have to check that out.
> 
> Can you provide Git/branch that I could use?

It applies cleanly here afaict - you double-checked that you updated
drm-intel.git? Just today I merged a pile of patches from Chris' series
here.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch