bauermann

For the moment I have to cope with a low-memory machine at home, so I decided to switch it from KDE to XFCE. But is it really worth it, in terms of memory savings? I decided to measure…

First of all, I’m not trying to do rigorous analysis here but just do some estimates to make a decision for personal use. Still, if you find something in my method which invalidates the results I obtained, I’d be glad to know about it.

To know the memory consumption of each desktop system, I simply started a fresh session in that desktop, opened a terminal and obtained a process listing with ps -e. No other program was opened at the time. Because I did this using a new user account, the test was made with the default configuration and default loaded programs of each desktop system.

Since the important figure in the ps output is the RSS (resident set size) column, I also turned off the swap partition in my computer. The ps manpage says that the RSS field doesn’t count swapped memory from the process. Good thing I noticed this before it was too late!

Here is the result for KDE:

program	vsz	rss
Xorg	23,936	18,304
kded	35,608	16,136
kdesktop	33,452	15,200
konsole	33,512	14,540
kicker	34,888	14,388
korgac	33,520	12,788
kwin	30,520	11,628
kpowersave	30,792	11,024
knotify	36,400	10,688
klipper	28,456	9,652
ksmserver	27,124	8,368
artsd	22,452	8,168
kaccess	27,212	8,028
seahorse-agent	20,828	6,608
klauncher	27,476	6,324
kio_file	26,048	5,376
gconfd-2	6,692	3,736
bash	6,368	3,728
kdeinit	25,764	3,516
dcopserver	25,616	2,916
startkde	4,300	1,492
gam_server	3,108	1,408
ssh-agent	4,508	724
dbus-daemon	2,760	532
kwrapper ksmserver	1,692	364
dbus-launch	2,916	340
total	555,948	195,976

And here is the result for XFCE:

program	vsz	rss
Xorg	27,776	20,788
gnome-terminal	43,652	16,860
xfdesktop	57,172	14,848
update-notifier	24,996	14,480
xfce4-panel	20,580	12,340
notification-daemon	19,156	10,224
xfce4-session	18,016	10,092
xfwm4	16,216	8,344
xfce4-menu-plugin	15,780	7,856
seahorse-agent	20,864	6,772
xfce-mcs-manage	18,812	6,148
gnome-volume-manager	18,108	4,744
Thunar	13,880	4,472
gconfd-2	6,692	3,776
bash	6,412	3,740
bonobo-activation-server	15,264	2,892
xscreensaver	4,240	1,936
/bin/sh /etc/xdg/xfce4/xinitrc — /etc/X11/xinit/xserverrc	4,292	1,444
gam_server	3,108	1,408
dbus-daemon	2,760	892
gnome-pty-helper	2,720	756
ssh-agent	4,508	728
dbus-launch	2,916	440
total	367,920	155,980

So, XFCE uses 152MB of RAM, versus the 191MB KDE uses. Not bad, almost 40MB (20%) less!

That’s not the whole story, though. I also wrote down the output of the free command as a sanity check.

Using KDE:

	total	used	free	shared	buffers	cached
Mem:	256112	245040	11072	0	20832	138236
-/+ buffers/cache:		85972	170140
Swap:	0	0	0

Using XFCE:

	total	used	free	shared	buffers	cached
Mem:	256112	251340	4772	0	20332	127156
-/+ buffers/cache:		103852	152260
Swap:	0	0	0

Look at the “used” column, in the “-/+ buffers/cache” line. That is the actual memory amount being used by the running programs in the computer.

This is a very interesting and surprising result: at the end of the day, XFCE actually uses more memory than KDE! Why, if adding up the resident sizes of the processes from each desktop system you get a different conclusion?

One explanation would be that KDE actually shares more memory between processes than XFCE. Its programs most probably have a greater number of shared libraries in common, which enables the kernel to use the same memory pages for the text section of those libraries accross process images. Unfortunately I didn’t collect data to test that possibility, and it’s late at night now. But it makes sense.

The bottom line, surprisingly enough, is that you should stick with KDE to preserve memory. Or switch to a bare-bones window manager instead of a complete desktop system, like IceWM, Window Maker, Blackbox or something else. But I’m too spoiled by the amenities of a good desktop to do that.

By the way, the tests were made with KDE 3.5.8 and XFCE 4.4.2 under Debian GNU/Linux unstable (updated on 2008/01/06) on a 32-bit x86 machine.

This entry was posted on Sunday, January 6, 2008 at 21:44 and is filed under english with tags hint, kde, linux, xfce. You can follow any responses to this entry through the RSS 2.0 feed You can leave a response, or trackback from your own site.