[RFC] Why Xorg waits for long time(200ms+) to invoke VT_RELDISP?

[Yu Chen]

Hi Adam,
thanks for your reply,
On Wed, Dec 7, 2016 at 2:17 AM, Adam Jackson <ajax at nwnk.net> wrote:
> On Thu, 2016-11-17 at 14:18 +0800, Yu Chen wrote:
>
>> May I know why Xorg takes 200ms+ before acking with VT_RELDISP?
>
> Because it's been asked to set the hardware back to text mode, which
> requires reprogramming the GPU, which takes time.
>
> 200ms is more time than it probably _should_ take, but you haven't
> specified (either in this email or in the bug you link to) what GPU
> this is and which driver you're using, so I can't be any more specific
> about what exactly is taking so much time and how it can be avoided
> without that.
The GPU is：
00:02.0 VGA compatible controller: Intel Corporation Broadwell-U
Integrated Graphics (rev 09) (prog-if 00 [VGA controller])
    Subsystem: Apple Inc. Broadwell-U Integrated Graphics
driver in use: i915
Xorg version:
X.Org X Server 1.18.3
Release Date: 2016-04-04

thanks,
Yu