Re: [PATCH] drm/i915: set IDICOS to medium uncore resources

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, 4 May 2012 23:00:32 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Fri, May 04, 2012 at 01:40:27PM -0700, Jesse Barnes wrote:
> > On Fri,  4 May 2012 18:58:59 -0700
> > Ben Widawsky <ben@bwidawsk.net> wrote:
> > 
> > > I'm seeing about a 5% FPS improvement across various benchmarks on my
> > > IVB i3. Rumor has it that the higher end parts show even more benefit.
> > > 
> > > This derives from a patch originally given to me by Bernard. The docs
> > > are  confusing about the definition names (ie. medium really seems
> > > like max), but it would seem it gives more cache to the GT at the
> > > expense of uncore. This configuration makes the split most in favor
> > > of the GT. I've not tried the other IDICOS values.
> > 
> > Bringing the IRC discussion here.  I think this is really at the
> > expense (though not really) of the CPU, since it allows the GPU to use
> > more of the shared CPU/GPU cache in the uncore.
> > 
> > You can fix up the #define names if you want; the MEDIUM etc may be
> > from an old, incorrect doc.  They were added awhile back.
> 
> Another perk from me: Can you do some benchmarking of this for snb, too?
> -Daniel

I didn't see such gains on my SNB. I ran half as many benchmarks, one
had almost 2% improvement, the other had a slight performance
regression.

Honestly, I'm a bit surprised by this, I may spend some more time to see
what happens.

-- 
Ben Widawsky, Intel Open Source Technology Center