Fast user switch applet causes high processor load

[Holger Berndt]

Binary package hint: fast-user-switch-applet

On Feisty, since a recent upgrade, the fast user switch applet causes 50% processor load on my AMD64 dual core when it is added to a gnome panel.

[Jochen Martin Eppler (jochen-eppler)]

see also bug #84944

[Christoph Konersmann (c-k-upb)]

This bug reapears on Ubuntu Gutsy (amd64).

HW: Intel Core2Duo 2x2,0GHz, 2GB RAM, 500GB SATA-HD
About 6 computers of the same system configuration.

The Installation is Gutsy for amd64 with newest packages for now (02.Okt. @ 15:49).

On login of a newly created user, the login hangs and "top" reports ~100% cpu-usage on one core. If f-u-s-a is removed from the panel all is ok. Readding the applet causes high cpu-usage again.

[William F Pearson (wfpearson)]

I can confirm it. Gutsy x386. Very frustrating because this is a laptop with no need to fast user switch.

[Matthew Gregg (mcg)]

I have both a Core2Duo running 64bit and a older P4 running 32 bit up to date Gutsy. Neither machine exhibits this problem. Both were upgraded from Fiesty.

[Christoph Konersmann (c-k-upb)]

The strace output while running is nothing more than

Process 6928 attached - interrupt to quit
brk(0x1213000) = 0x1213000
brk(0x1234000) = 0x1234000
[...]
Process 6928 detached

[Christoph Konersmann (c-k-upb)]

Hm, maybe this high CPU usage is caused by the userdatabase? All systems are connected to a ldap, kerberos, AFS infrastructure with many user entries. Does this applet preload all users available from "getent passwd"?

[William F Pearson (wfpearson)]

Christoph: That's an interesting question because "getent passwd" loads every user on my Win 2k3 domain. This machine is authenticated to the domain controller via Samba ADS.

# getent passwd
...
real 0m2.246s
user 0m0.016s
sys 0m0.012s

#time getent passwd |wc -l
3964

Thats a lot of users!

Is there a way to limit fast-user-switch to local users only? Certain proprietary applications require me to be authenticated to the domain or I wouldn't need Samba ADS at all.

[Tassos Bassoukos (abassouk)]

This happens at my installation too (getent gives ~10k registered users). When logging with a local user and the network disabled all is ok, but if the network is enabled the panel freezes on login and the fast-user-switch-applet task runs at 100%. Now, I can't remove the package as ubuntu-desktop depends on it, and while I've removed the applet from the default environment, there is no easy way to remove it from users desktops automatically on login...

[Marcel Schaal (marcelschaal)]

We can confirm this bug having about 2500 users. Also we don't want to remove ubuntu-desktop because other packages may get removed by apt-get autoremove.

[puntium (puntium)]

Can also confirm similar behavior on a NIS-based system with 6000+ users. fast-user-switch applet takes up all CPU, and locks up the gnome panel.

[Mike Peters (mike-ice2o)]

I'm seeing something similar on Gutsy (AMD64) with only 4 local users. CPU usage goes to 100% as soon as I select another user from the list.

strace shows the following when I try the user switch:

sendto(19, "FLEXI_XSERVER_USER ozlem\n", 25, MSG_NOSIGNAL, NULL, 0) = 25
ioctl(3, FIONREAD, [0]) = 0
poll([{fd=4, events=POLLIN}, {fd=3, events=POLLIN}, {fd=8, events=POLLIN|POLLPRI}, {fd=10, events=POLLIN|POLLPRI}, {fd=11, events=POLLIN|POLLPRI}, {fd=12, events=POLLIN|POLLPRI}, {fd=14, events=POLLIN|POLLPRI}, {fd=13, events=POLLIN|POLLPRI}, {fd=16, events=POLLIN|POLLPRI}, {fd=15, events=POLLIN|POLLPRI}, {fd=18, events=POLLIN}, {fd=17, events=POLLIN|POLLPRI}], 12, 0) = 0
read(19, 0x7fff4f646c9f, 1) = -1 EAGAIN (Resource temporarily unavailable)

Is the \n supposed to be there with the user name in the call to FLEXI_XSERVER_USER?

[Pedro Villavicencio (pedro)]

Fixed upstream, thanks.

[Wouter Stomp (wouterstomp-deactivatedaccount)]

Fixed: this should now be in ubuntu.