Re: [PATCH 2/2] drm/i915: load a ring frequency scaling table

[Chris Wilson <chris@chris-wilson.co.uk>]

On Fri, 24 Jun 2011 11:13:14 -0700, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> The ring frequency scaling table tells the PCU to treat certain GPU
> frequencies as if they were a given CPU frequency for purposes of
> scaling the ring frequency.  Normally the PCU will scale the ring
> frequency based on the CPU P-state, but with the table present, it will
> also take the GPU frequency into account.

So it wasn't picking up max-cpu-freq even though I have CONFIG_CPU_FREQ
and the various ACPI and Intel cpu drivers.

Taking a hint from x86/kvm, I used tsc_khz instead of the default 3000.

nexuiz @10x7  nopatch -> 3000 -> 3300 [tsc_khz]
uncached:     43.2       44.4    44.8
     llc:     51.3               52.3

At max_freq=3000, a cpu busy loop was still able to nudge it up to the
same speed as using the max_freq=3300 value.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre