slight lags in youtube video 1080p since a change in kernel 4.15 related to drm/ttm

Submitted by Barto

Assigned to Default DRI bug account

Link to original bug (#105038)

Description

Created attachment 137264
dmesg

Hello,

I have a radeon HD4650 pcie, I use the radeon driver,

since a new algorithm for drm/ttm introduced in kernel 4.15.x then I notice a performance loss in video playback, especially when the format is 1080p ( for example youtube video ), some lags are visible ( for example travelling images, vertical scroll of the credits in a video ),

the bug has been introduced since this commit :

commit 648bc3574716400acc06f99915815f80d9563783
Author: Christian König christian.koenig@amd.com
Date: Thu Jul 6 09:59:43 2017 +0200

drm/ttm: add transparent huge page support for DMA allocations v2

Try to allocate huge pages when it makes sense.

v2: fix comment and use ifdef

Signed-off-by: Christian König christian.koenig@amd.com
Reviewed-by: Felix Kuehling Felix.Kuehling@amd.com
Signed-off-by: Alex Deucher alexander.deucher@amd.com

reverting this patch solves the bug,

I have created a bug report in kernel's bugzilla :
https://bugzilla.kernel.org/show_bug.cgi?id=198511

Christian König advices me to open a bug report here for drm/radeon,

I have filmed my screen in order to demonstrate the effect of this bug, you can see my video here :

https://www.youtube.com/watch?v=YqtleU5YBlA

Attachment 137264, "dmesg":
dmesg.txt