Re: Noticeably poor Intel GPU performance on 3.3 and 3.4 dom0 kernels

[Joanna Rutkowska <joanna@invisiblethingslab.com>]

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On 05/30/12 12:37, Jan Beulich wrote:
>>>> On 30.05.12 at 12:14, Joanna Rutkowska <joanna@invisiblethingslab.com> 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?

With mem=4G xen option, the graphics performance is just as poor as without.

joanna.


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