Bug 320210

Summary:	kwin cpu usage whilst switching between virtual desktops which have several windows open
Product:	[Plasma] kwin	Reporter:	pauloedgarcastro
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	major
Priority:	NOR
Version:	4.10.2
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Output of "qdbus org.kde.kwin /KWin supportInformation"

Description pauloedgarcastro 2013-05-24 11:16:16 UTC

Hi all.

I have many ( > 20 ) different windows open in each one of the 8 virtual desktops I have set up.

Lately, or at least since the upgrade to Fedora 17, I think I've noticed that switching between virtual desktops, specially if I'm switching to one which has many windows open, seems to be a very expensive process.
Sometimes it can take up to 5 secs until I can get something to be written in the default focus window.

It's almost like kwin is enumerating all the windows in this new desktop that it switched to ( hich makes some sense ), but doing it at a very high cpu cost.

The kwin,X processes seem to use a lot of CPU whilst the process of switching is happening.

If we couple this with some extra load coming from some other process say Firefox, or some heavy IO operation for instance, then the system becomes almost unusable from the perspective of someone who's frequently changing from virtual desktop to another.

This didn't used to be the case some months ago...

I'm on Fedora17.
kde-workspace-4.10.2-4.fc17.x86_64
kernel-3.8.8-100.fc17.x86_64

Reproducible: Always

Steps to Reproduce:
1. Login to the system, open many ( > 20 ) windows ( Konsole, emacs, okular, firefox ) in different desktops
2. Switch from one virtual Desktop to another
3. Evaluate how long it takes to be able to write something in the default window
Actual Results:
General slowness all across the UI

Expected Results:
I would have expected the system to be able to cope

Whilst this slowness is happening there's no swap space being used.

Comment 1 Martin Flöser 2013-05-24 11:38:38 UTC

please provide output of:
qdbus org.kde.kwin /KWin supportInformation

Comment 2 pauloedgarcastro 2013-05-24 12:13:06 UTC

Created attachment 80055 [details]
Output of "qdbus org.kde.kwin /KWin supportInformation"

Adding the output of 
qdbus org.kde.kwin /KWin supportInformation
as requested.

Comment 3 Martin Flöser 2013-05-24 12:28:44 UTC

Please try enabling desktop effects, this should fix the problem.

Comment 4 Thomas Lübking 2013-05-24 12:33:18 UTC

Also: what decoration do you use?
(we should have that in the support info ;-)

Comment 5 Martin Flöser 2013-05-24 12:59:12 UTC

> (we should have that in the support info ;-)
it's on my TODO list, maybe I should once pick that todo

Comment 6 pauloedgarcastro 2013-05-24 13:30:59 UTC

Turning on the desktop effects does seem to improve the situation massively.
I always had those off as I associated them with extra CPU being diverted into the window manager to do all the fancy animations...
It never really occurred to me that enabling them would speed up the general user experience.

As for the decoration, if I understand correctly, I am using Plastik.

( 30 mins later ) 
So far so good, and assuming this will hold at the next reboot which I'm sure it will as far as I'm concerned this is fixed.
Many thanks.

Comment 7 Thomas Lübking 2013-05-24 13:48:39 UTC

(In reply to comment #6)

> As for the decoration, if I understand correctly, I am using Plastik.
Don't use Aurorae themes (this nowadays also includes Plastik) with the native graphicssystem or without compositing.

*** This bug has been marked as a duplicate of bug 313016 ***