Re: IVB GPU turbo

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Tue, 22 May 2012 17:14:11 +0100
Joe Bloggsian <joebloggsian@gmail.com> wrote:
> Thanks for the help, I've had time to build and test a few kernels on
> various systems following your advice.
> 
> In summary I need both a new drm-intel-next kernel from Daniel's tree *and*
> the patch you suggest to get expected GPU turbo behaviour, compared to a
> stable 3.2 kernel.
> 
> Test results from Core i7 3770 / HD4000: With just the latest drm-intel-next
> kernel (commit 98b6bd), the symptoms are as before, max GPU turbo of 600MHz
> in the test app. With just the (equivalent of the) patch applied to a
> 3.2.18 kernel, the max turbo is better (>600) but still often less than
> expected. With both patch and kernel, the GPU immediately spins up to
> 1.15GHz and stays there, as expected - and the measured test app
> performance is nearly twice what I get with the up to date Ubuntu 12.04 x64
> kernel!

Awesome, thanks so much for testing, I'll send the patch upstream now.

> I've also seen the full turbo kick in for other media workloads with the
> default kernel, but one way of reliably reproducing this problem for me is
> to run the avcenc test app that is part of libva.
> 
> The same problem exists on Sandy Bridge. Although the turbo and performance
> gaps between the latest released Ubuntu 12.04 kernel and the patched 3.4
> kernel are less than Ivy Bridge, they are still significant on my core i3
> 2310M / HD3000 laptop.

Ok good to know; the patch will apply to SNB too, the fact you tested
things there makes my life easier. :)

-- 
Jesse Barnes, Intel Open Source Technology Center