I work as a Java programmer, so I often have to run several programs at the same time that consume a lot of memory.
When my memory is full and Linux starts swapping, my computer almost completely freezes. I can see that it is heavily writing on the hard-disk and everything reacts really slowly, often not at all. Moving the mouse in X sometimes doesn’t work at all, sometimes it has a delay of several seconds, clicking usually has a delay of several minutes. Sometimes it is possible to change to the TTY (with a long delay), there I can usually type without delay, but when I try to log in, it takes several minutes after typing in the user name until the password prompt appears, and usually an error message appears that tells me that the login timed out. So the only possibility is usually to restart the computer.
I noticed that other intensive writing to the hard disk also significantly slows down my computer. Sometimes, I used rsync to limit the bandwidth when I copied files around on my own computer, as else the system would be almost unusable.
How can this be? At the moment it seems more useful to me to completely turn off swapping. That might crash some processes, which is unfortunate, but the alternative at the moment is to crash all processes by turning off my computer.
I am using Gentoo Linux with kernel 3.6.2-gentoo, I have a 10 GB swap partition on a HDD.