I'm using Slackware64-13.37 on a new ASUS mobo (can't recall mobo number) with Intel i5-2400 cpu @ 3.1 GHz, 8 gig memory and 5 Tbytes drive space. The computer is heavily used as a firewall/gateway for the home network and as a data storage device for music, photos etc.

When I first start KDE everything is fine .. windows move smoothly and htop shows about 8% total cpu usage. After a day or so however, things start to slow down. Windows move in a very jerky fashion and htop now reports approximately 25% cpu usage.

I'm using exactly the same software at work (except for the ip forwarding stuff) and have no such problems there.

I've been trying to find the source of the problem for weeks but haven't had any real success. Turning off compositing helps a bit but not to the extent that I think it should. Any ideas?

I would disable akonadi/nepomunk/strigi (desktop search etc). Also run Xfce for a day or so to see if its X or KDE.

I think I finally found the cause of the slowdown. Had to replace an ethernet card that was slowing the network down and ... voila! no slow X11 anymore. Everything is looking good so far. Who'd have thunk that a wonky ethernet card would do something like this.