Bug 787483

Summary:	Desktop and applications really slow when switching between users
Product:	[Fedora] Fedora	Reporter:	Jon Dufresne <jon.dufresne>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	16	CC:	gansalmon, itamar, jforbes, jonathan, kernel-maint, madhu.chinakonda
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-03-15 15:02:28 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description Jon Dufresne 2012-02-05 16:33:39 UTC

Description of problem:
My desktop is shared between two users. We are both always logged in. We will frequently switch from one user to the other using the key combination Ctrl + Alt + Fx. Usually after the first day, switching between users causes the newly shown desktop to respond extremely slowly. After some time (caching?) the desktop responds at normal speed. That is, until we switch to the other user.

I am not sure what output to capture to help diagnose the issue. But if you instruct me to provide any information I would be glad to help.

Version-Release number of selected component (if applicable):
kernel-3.2.2-1.fc16.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Log in as one user, open applications
2. Log in as a second user, open applications
3. Let OS run for a day
4. Switch to other user using Ctrl + Alt + Fx
5. Notice desktop responds very slowly
6. After five minutes desktop responds at normal speed
  
Actual results:
Desktop is slower than it should be.

Expected results:
Desktop responds as normal when switching between users.

Comment 1 Justin M. Forbes 2012-03-14 20:23:13 UTC

Sounds very much like you are running out of memory. Applications have moved to swap, and once you switch users it takes a while to switch the current user applications from swap space.  The output of 'free' would verify.   Remember, when you switch users, all of the other user applications are still in memory and with web browsers especially, the memory footprint can grow significantly over time.

Comment 2 Jon Dufresne 2012-03-15 01:06:36 UTC

Here is the output of free after experiencing this issue:

$ free
             total       used       free     shared    buffers     cached
Mem:       4041576    3926236     115340          0      21120     236620
-/+ buffers/cache:    3668496     373080
Swap:      6160380    2850216    3310164


Output of the top sorted by memory usage:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND            
 1814 root      20   0 2958m 1.2g 2600 S 10.0 31.1 721:51.35 Xorg               
 6562 jon       20   0 1466m 421m  19m S  0.3 10.7  44:00.36 firefox            
23508 laura     20   0 1048m 242m  18m S  1.3  6.1   1:40.59 firefox            
 2653 jon       20   0 1994m 186m  10m S  0.0  4.7  97:22.83 evolution          
 2201 jon       20   0 1946m 105m  14m S  3.3  2.7 249:44.06 gnome-shell        

> when you switch users, all of the other user applications are still in memory
> and with web browsers especially, the memory footprint can grow significantly
> over time.

Understood.

This lag between switching users makes the multi-user experience a serious drag. It is quite frustrating to switch users, then experience no desktop response for ~30-60s. I never recall experiencing such a delay until F16 (possibly F15). Does my system have a small amount of memory for the usage? Are the top memory users using more memory than expected?

If there is any additional output I can capture to diagnose the issue, or possible memory leaks I would be happy to collect the data.

Hardware profile: http://www.smolts.org/client/show_all/pub_621c77b7-dfc4-4b1f-b643-19efd5fbe185

Comment 3 Justin M. Forbes 2012-03-15 15:02:28 UTC

There is nothing to diagnose, look at the amount of swap you have in use.  It is clearly not enough memory to support 2 users without swapping.  And things like firefox will keep growing the memory footprint over time. If you leave pages like facebook open, it can get insane.  4GB of memory is sufficient for single user desktop usage typically. Switching users you are probably going to want at least 6.  Unfortunately this is a reality with "web 2.0" and not a Linux issue that can be easily resolved.  Browsers eat memory in pretty much any OS.