Android system RAM usage
These things helped a lot :


Looking at which apps drained the most power. Performance improved a lot after uninstalling Facebook and a few other apps I had downloaded over time.
Upgrading to CyanogenMod 10.1-M3 helped. They fixed a nasty memory leak, which probably accounted for parts of my issues.
A little before the first 10.1-RC candidates, the CM team tweaked memory settings that had changed without warning in one of the releases.
If you're running low on storage, you might want to run fstrim /data on a root shell. It seems to be a technical limitation of SSDs when they're low on space.