Sorry if this is the wrong place to put this.

Right, I had left my computer idle for a good while and went back to it. When I started using it it seemed pretty sluggish. Initially suspecting strigi I checked the icon in the systray - but no: strigi file indexing was suspended.

I hit ctrl-esc to check the system activity monitor, and I found a process nepomukservicestub eating up my CPU at ... wait, only 5%? It was the largest thing there as well. (well kwin and plasma-desktop would jump up and down)

Suspicious, I decided to check htop. htop reported a very different figure than 5% - a shocking 50%, which would fluctuate to levels ranging from 20%-80%.

I decided to ignore it, and after a while nepomukservicestub just stopped doing whatever it was doing and my computer resumed its responsiveness. However there are a couple questions:

1) What was nepomukservicestub doing if indexing was suspended?
2) When will it do this stuff? Only when I'm idle or during pre-scheduled times?
3) Is there a way to disable this?
4) Why does the system activity monitor report very different readings than htop? (htop seeming more realistic)

While I do not know about the first 3 questions, it is known that System Activity Monitor ( aka KSysGuard ) uses the same incorrect methods for getting information about a process that top and ps use.

My solution to disable Nepomuk I don't use is this one:

sudo rm /usr/bin/nepomuk*
sudo rm /usr/lib/kde4/*nepomuk*
sudo rm /usr/share/kde4/services/*nepomuk*

Warning to all about L_V's method: this bypasses your package manager and may cause problems for it when upgrading, removing or installing additional packages and could lead to broken dependencies.

Ok, I have no intention of using L_V's method, but I caught it red-handed!

http://upload.failnation.com/files/1/snapshot4.png

Unfortunately I do not know much about Nepomuk or why it would be accessing the system even when "Indexing is suspended". As you were not using the system at the time, your actions cannot of triggered it, so please file a bug report at bugs.kde.org.