Slow performance using eGPU with lid closed

[Qu Wenruo]

On 2019/5/7 下午5:16, Michel Dänzer wrote:
> On 2019-05-05 3:06 a.m., Qu Wenruo wrote:
>> On 2019/4/29 下午10:11, Michel Dänzer wrote:
>>> On 2019-04-29 3:04 p.m., Qu Wenruo wrote:
>>>
>>>> Is it possible to disable Intel one completely at X start time?
>>>>
>>>> Just regular xorg.conf.d with amdgpu only device section?
>>>
>>> Sure, but then you won't be able to power down the AMD GPU while Xorg is
>>> running (or at least while it's active).
>>
>> Considering current kernel eGPU support, hot unplug is impossible as it
>> will panic the amdgpu module, so it's not a big deal.
> 
> FWIW, another possible gotcha is that DRI_PRIME=1 will result in apps
> using the Intel GPU for rendering then.
> 
> 
>> While the bigger problem is the config. As normally Xorg auto detect is
>> good enough and user needs no extra config.
>>
>> But with such eGPU setup, if only have 10-amdgpu.conf and 20-intel.conf,
> 
> Unless you've modified it, 10-amdgpu.conf just instructs Xorg to use the
> xf86-video-amdgpu driver for any devices controlled by the amdgpu kernel
> driver by default; it doesn't affect which GPU Xorg uses as primary.
> 
> Where is 20-intel.conf from, and what does it contain?
> 
> The xorg.conf.d mechanism is for shipping configuration snippets in
> packages. For user configuration, /etc/X11/xorg.conf should be used.
> 
> 
>> without screen specification, X will not start due to failure to find
>> screen.
>>
>> I'm wondering what's the correct way to specify all the needed config.
>> to make X work with, and without eGPU.
> 
> This should be all you need to choose the primary GPU:
> 
> Section "Device"
>         Identifier "AnythingYouLike"
> 	BusID	"PCI:<as printed in Xorg log file, e.g. 34 at 0:0:0>"
> EndSection

This works like a charm!

The only extra thing I need to do is creating a small script for lightdm
display-setup-script to generate Xorg.conf according to whether the eGPU
is present.

As the BusID doesn't work well if eGPU is not present, X will refuse to
start and require all framebuffer devices to be specified.

Thanks,
Qu

> 
> 
> If you don't want Xorg to use the non-primary GPU at all (it can still
> be used via DRI3), add
> 
> Section "ServerFlags"
>        Option	"AutoAddGPU" "off"
> EndSection
> 
> 

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