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This really puzzled me. I noticed à 30% of avahi daemon on Kubuntu 10.10 on a Lenovo T410 (this is the value given by top, not by the task manager of krunner).

This was far too high. Trying to supress plasmoid one by one I managed to narrow down the CPU usage to the system tray. Then I did a few more test and actually everything is just until is open the Network manager in the system tray and log to my wired connection. So it seems that asking kubuntu to use a wired connection make the avahi daemon using 30% of the CPU. Turning it down doesn't make it down afterward.

Do you knwo what could cause this problem? Anyone else realised that?

EDIT: After a few more test I can confirm this is really a problem due to wired connection, it doesn't do that with a wireless connection.

EDIT#2: I checked from home. This is not a problem with every eth0 connection. At home where dhcp works I don't see the boost in CPU usage. It's only from work, where I add to manualy enter the ip adress gateway et al. Also removing the internet cable drop the cpu usage down. Very strange.

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maybe you should change the tags: add avahi (is there such a tag?), remove plasma? – user unknown Mar 25 '11 at 22:30
done thank you. – Noz Mar 26 '11 at 8:44
The problem was actually a problem of the network at work. A bad configuration of a printer was overloading the netwrok. The problem got detected with "tcpdump" command. So this is not a question anymore. Should I delete it or something? It is still good to know that such a problem can cause network-manager to work a lot. – Noz Mar 30 '11 at 5:21
It's perfectly okay to answer your own question and to mark it as the valid answer. That way, you might attract people with the same question but without solution. – user unknown Apr 1 '11 at 17:41
up vote 0 down vote accepted

So in the end the problem was that there was too much traffic on the network caused by a badly configured printer. The overload of packets and the adress of the printer was detected by "tcpdump" command.

I understand that in the end the problem was neither due to ubuntu nor linux. But still, if one detects some high CPU usage from network-manager on a shared network (again it appears as avahi task on "top") it can be because of a problem of traffic on the network.

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