Bug 198241

Summary:	Intel graphics performance regresses after upgrading to kernel 4.14
Product:	Drivers	Reporter:	Julien Langlois (LANGLOIS.JF)
Component:	Video(Other)	Assignee:	drivers_video-other
Status:	RESOLVED INVALID
Severity:	high	CC:	pmenzel+bugzilla.kernel.org
Priority:	P1
Hardware:	Intel
OS:	Linux
Kernel Version:	4.14.*	Subsystem:
Regression:	Yes	Bisected commit-id:

Description Julien Langlois 2017-12-23 21:36:23 UTC

After switching to kernel 4.14, the screen has flickering and response rate in Xorg is sluggish. The only change is 4.13->4.14. Graphics run smoothly in 4.13.

As a data point, running glxgears produces consistent 60 FPS in 4.13, and around 40 FPS in 4.14 (screen refresh is set to 60Hz in both cases).

- system: "x86_64-linux"
- host os: Linux 4.14.0, NixOS, 18.03pre120540.b8f7027360 (Impala)
- multi-user: yes
- HP Spectre x360 Kaby Lake (13-w063nr)
- Intel(R) HD Graphics 620 (Kaby Lake GT2)
- Issue presents itself with and without compton running

See https://github.com/NixOS/nixpkgs/issues/31999

Comment 1 Julien Langlois 2017-12-31 20:00:39 UTC

As reported in the other bug report, commit dc911f5bd8aacfcf8aabd5c26c88e04c837a938e introduces the issue by using an "alternate fixed mode."

Comment 2 Paul Menzel 2018-01-02 09:58:33 UTC

Please paste the output of `xrandr` of 4.13 and 4.14, and attach the rest of the files asked for in [1].

[1] https://01.org/linuxgraphics/documentation/how-report-bugs

Comment 3 Jani Nikula 2018-01-02 17:10:53 UTC

(In reply to Paul Menzel from comment #2)
> Please paste the output of `xrandr` of 4.13 and 4.14, and attach the rest of
> the files asked for in [1].
> 
> [1] https://01.org/linuxgraphics/documentation/how-report-bugs

And file the bug at https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel