CPU hogging when external screen connected

[Michał Sawicz]

CPU usage of u-s-c goes to around 40% when an external screen is connected, as long as the display is on.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: unity-system-compositor 0.2.0+15.04.20151008.1-0ubuntu1 [origin: LP-PPA-ci-train-ppa-service-stable-phone-overlay]
Uname: Linux 3.4.0-5-flo armv7l
ApportVersion: 2.17.2-0ubuntu1.3touch1
Architecture: armhf
Date: Thu Oct 29 12:40:04 2015
GraphicsCard:

InstallationDate: Installed on 2015-10-29 (0 days ago)
InstallationMedia: Ubuntu 15.04 - armhf (20151029-020304)
SourcePackage: unity-system-compositor
UpgradeStatus: No upgrade log present (probably fresh install)
version.libdrm: libdrm2 2.4.60-2
version.lightdm: lightdm 1.14.2-0ubuntu1.1
version.mesa: libegl1-mesa-dev N/A

[Michał Sawicz (saviq)]

Seems android-specific, not reproducable under mesa.

See excerpt from top with threads:
http://pastebin.ubuntu.com/12998801/

[Alexandros Frantzis (afrantzis)]

Added Mir to affected projects since chances are this is a Mir problem rather than a USC-specific problem.

[Alberto Aguirre (albaguirre)]

It's probably this: https://bugs.launchpad.net/mir/+bug/1499039

[Michał Sawicz (saviq)]

Well, even if it's that, should compositing ever do 40% CPU?

[Alberto Aguirre (albaguirre)]

Yep, duplicate of lp:499039, fixing lp:499039, USC cpu consumption (as reported by top) goes down to normal when an external display is connected.

[Alberto Aguirre (albaguirre)]

I meant lp:1499039 above.