The delay between your question and my answer means that I did a lot of
updates, zram ist working now,
A good description on how to test zram can be found at:
http://www.webupd8.org/2011/10/incre...inux-with.html
and an overview at Wikipedia at
http://en.wikipedia.org/wiki/ZRam
Knoppix 7.0.1 will use 75% of the available RAM, but at maximum 4GB, for
compressed swapspace in ram. In the best case, you can double or triple
your "virtual working RAM" with zram without swapping to disk. In the
worst case, you lose a few header bytes due to incompressible data, or
get "out of memory" kills (like before, without zram) when even
compressed swap runs out of space.
75% seems to be a decent number for me. I don't trust a "fully
compressed" RAM like recommended in the URL given above, since you
always need some extra MB as immediately available "emergency RAM"
without having to negotiate with the swap area. In my tests, I got
strange effects when using 100% of the available Ram as zram space, like
ramdisks suddenly being "full" with no data inside.