Hotplug polling causing pageflip jitter. Fixed in v3.9
** Changed in: xserver-xorg-video-intel (Ubuntu)
Status: New => Fix Committed
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https://bugs.launchpad.net/bugs/1077512
Title:
xserver-xorg-video-intel regression, video playback not smooth on
external display after video driver update
Status in “xserver-xorg-video-intel” package in Ubuntu:
Fix Committed
Bug description:
Hardware
---------------
- HP Probook 4510s Laptop (Dual core Intel Celeron) with Intel internal
graphics GM45 (Mobile Intel GMA 4500MHD).
- Sony KDL-32W4000 TV as external display, resolution 1920x1080, connected to
laptops HDMI - port. The brand of the external display probably has nothing to
do with the bug.
Software
--------------
- Ubuntu 12.04.1 LTS
Description of the bug
--------------------------------
- Happens only if external HDMI display is connected to the laptop.
- Started to happen when Ubuntu 12.04 (x86_64) delivered the first update to
package xserver-xorg-video-intel, the version that shipped with Ubuntu 12.04
release did not have this bug.
- The display updates stops for a brief moment (approximately 5 - 10 frames).
- Happens continuously repeating every 10 seconds.
- kworker - process seems to do something modestly intensive always when the
display glitch happens.
- If you move the mouse pointer in a circle slowly with a continous speed,
you can see that even the mouse pointer stops briefly every 10 seconds.
- The bug dissapears if I downgrade my xserver-xorg-video-intel driver to the
version that originally shipped with Ubuntu 12.04 (xserver-xorg-video-intel
version 2:2.17.0-1ubuntu4)
How to reproduce the bug
--------------------------------------
- Attach an external 1920x1080 display to the HDMI - port of the laptop.
- Install Ubuntu 12.04.1. Note: do not install updates during installation.
- Install mesa-utils as we need the program glxgears to see the display
glitch. You can see the buggy behaviour also playing any sort of video, but its
easiest to see with glxgears.
- Install synaptic because it can be used to easily force install different
versions of the video driver.
- After installation run synaptic and search for the package:
xserver-xorg-video-intel verify that driver version is 2:2.17.0-1ubuntu4
- Run glxgears and note that the 3D-gears it displays spin totally smoothly
all the time.
- Install all Ubuntu updates and reboot
- Run glxgears and note that every 10 seconds the gears stops spinning for a
brief moment and then jump forward a couple of frames. If you have top running
you can see that every time the display glitch happens kworker jumps up in the
process list, it does not consume much processor power but this seems to happen
at approximately the same time as the video glitch.
- Run synaptic, search for xserver-xorg-driver-intel and note that the
version is 2:2.17.0-1ubuntu4.2. Select the driver package and click on the
"Package" - menu and select option "Force Version", select version
2:2.17.0-1ubuntu4 and apply.
- Now that we have the old driver installed, boot and run glxgears to see
that the video glitch is gone.
- Install all Ubuntu updates (this updates just the intel video driver as we
just installed all the other updates) to see that the problem comes back, when
the intel driver is updated.
Things tested that don't have any affect, the buggy behaviour remains
---------------------------------------------------------------------------------------------------
- Selecting a smaller resolution (1280x1024) for the extrenal display instead
of the native 1920 x 1080.
- Mirroring laptop internal display to the external display (forces both
displays to the resolution of the internal display).
- Using Ubuntu System Settings / Displays to turn of external or laptop
internal monitor does not help, the display glitch is still there.
- The bug happens also in Ubuntu 2D.
- The bug happens also in Gnome Classic (No effects).
Things tested that have an affect, the buggy behaviour goes away
--------------------------------------------------------------------------------------------
- Starting up the computer without the external monitor. The bug is still
there but the display glitch is very mild, meaning that the display still stops
updating every 10 seconds but the stop is very very short, missing just 1 or 2
frames.
- Downgrading intel xorg driver to 2:2.17.0-1ubuntu4. After downgrading to
the version of the driver package that originally shipped with Ubuntu 12.04 the
display glitch goes away.
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