I installed Krita 2.9.11 on Debian 8, following the tutorial of the cats by David Revoy. My computer is an old one, with only two gb of RAM. Everything is allright, except when I use ctrl+z for undoing the latest things made in Krita. The undo is very very slow and in the same time the computer stops, and I have to wait a few seconds to make something in the program. I am thinking to disinstall Krita 2.9.11 and install the last version in Debian Jessie repositories, the 2.8.5. What do you suggest to me?

It's reasonably fast here, but 2 GB of RAM is very very little for krita. I suggest getting more RAM.

Yes, with 2gb of ram, the undo information likely immediately gets swapped out to disk, which means that on undo, it needs to be read in again.

maryonn, can you firmly confirm, that 2.8.5 version have fast undo and 2.9.11 - slow?

It can depend on other software running in background (youtube video in browser, size of canvas in Krita and history of operations) and depend on everything, so version comparison should be done at same time without reboot/pauses, or it should tried many times.

Thank you for your replies. Yes, 2 gb ram is very little. This is not the only computer I have, but I want to use it, too. I think that you are right, it is better to get more ram, if it is possible.