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Re: [Xen-devel] Noticeably poor Intel GPU performance on 3.3 and 3.4 dom0 kernels

>>> On 30.05.12 at 12:14, Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx> 
>>> wrote:
> I've recently been some newer Dom0 kernels (3.3.5, 3.4) under Xen 4.1.2,
> and have noticed that those kernel noticeably downgrade performance of
> (at least) Intel GPUs. This is easily noticeable even on such trivial
> tasks as scrolling a webpage in Firefox or Chrome. This slow GPU
> performance on 3.3 and 3.4 kernels is in stark contrast with what I see
> on 3.2.7 Dom0 kernel, where graphics works just great...
> In order to make sure that this is not caused by power management set
> too strictly, I played with xenpm and made sure to set the following:
> 1) xenpm set-scaling-governor performance
> 2) xenpm set-max-cstate 0
> I have verified then that my processor: 1) keeps staying in P0 state
> (so, max frequency), and 2) keeps staying in C0 state.
> Those setting didn't change anything regarding the poor graphics
> performance, though.
> Any ideas what else I could test to find out the cause of this?

To check whether the DRM drivers' supposedly more extensive
use of the DMA API is the reason, could you check whether the
performance is as bad with "mem=4G" on the Xen command line?


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