Seeing as I've been bitten by KDE4 performance issues on netbooks (and low-end laptops), I thought I'd start a thread for ideas on improving KDE performance on low-end computers.

Now, for starters, I'm going to define a "low-end computer" here as any computer that meets the following specifications:
- A CPU clockspeed between 400 and 1600 MHz
- 1 to 2 CPU cores
- 256 MB to 1 GB of RAM
- Video hardware that uses shared memory, or is more than 5 years old.

This is pretty arbitrary (and maybe broader than necessary), but I think it works. The idea here is that, if you have a computer built within the last decade, you should not have to buy a new computer in order to get a decent experience with KDE; nor should you have to make non-obvious changes (e.g. exporting environment variables, altering .desktop files) to KDE in order to make it faster.

So... What changes do you think might improve KDE's performance on hardware such as I've specified, without compromising functionality or requiring dirty hacks?

I hear a lot about speed problems on netbooks, but I haven't had too much trouble and I have kontact, amarok, kopete, skype, and a few other utilities always running in the background. I will admit that I spent the extra $20 and upgraded the RAM to 2GB, so that could make a difference. Also, I don't really use too many current computers so maybe expectations have changed, but it's at least as snappy as my parents' computer which is, I think, about five years old and running software of that era.

But I do do a few things:

One thing that helps a lot is to keep up with the latest releases. I'm running openSUSE 11.4/Tumbleweed and there was some update introduced after the 11.4 release that made a noticeable improvement.

I also turn off the blur and wobbly windows effects, but leave on transparency. Dragging windows isn't quite as smooth as it could be, but I make enough use of the transparency effect that it's worth it. (Also, it's mostly only an issue when I connect a second monitor since I usually maximize windows on the netbook's screen, but the dual monitor support is buggy enough that I don't even notice speed issues...)

Also, I don't use rekonq, which is becoming the default browser for the KDE environment in some distributions. I'm trying it again right now and it still has issues producing a responsive interface on my computer. For example, I'll click the stop button and not see any indication that I did anything for a few seconds, or I'll be faced with a blank window on an already loaded tab while I wait for a different tab to load. To be fair, though, openSUSE Tumbleweed is still using version 0.6.1, so maybe things are better in 0.7. But, I've had good luck with Chromium and the latest Firefox, but I'm a big fan of Opera. The only trouble with Opera is that I can't quite get it to integrate with kwin's tabbing.


EDIT: Also, a year or so ago (or more, time flies...) I tried out KDE on Fedora, Kubuntu, and openSUSE (using their respective services to upgrade to the latest KDE SC) on my computer, and my experience was that things were much snappier under Kubuntu and openSUSE than Fedora. A lot can change in that time, so my only point is that there can be a difference between distributions.

0. If you have <= 2 GB of RAM, forget about 64 bit installs.
1. Keep Nepomuk under 128 MB of RAM usage. Performance will suffer, but with defaults (50 MB) it's acceptable.
2. Ensure you have the LATEST STABLE KDE SC. There are massive performance differences between KDE SC 4.6.0 and 4.6.3, on Nepomuk (including the 100% CPU Nepomuk megabug killed in 4.6.1)
3. Disable hard drive indexing, or limit it to the essential. You need 1 GB of RAM to fully use it.
4. If you really want hard drive indexing, ensure you're using Strigi 0.7.3. No distro packages that, so you'll need a snapshot from KDE Git. There are healthy performance increases with that release. Also, ensure yourself you have Akonadi 1.5.3: you need every bit of performance.

About distros: my favourite one is Fedora, it's the most secure and the Fedora KDE packaging team rocks, but, if you really need speed and low resource usage while preserving the full KDE experience, Chakra is your baby. A little young and temperamental, but nothing beats its speed and low RAM usage, gained through intense meditation and GTK removal sessions.