When Linux starts swapping you're basically doomed. Very soon the system won't react to any input any more, but happily swap on until the end of days...

Can you think of a command that holds all processes whatsoever, thus (and while) allowing you to open a clean shell where you can examine the source of the problem and kill the process which ate up all the memory? (I guess this won't be easy, because as the memory is probably completely filled up you'd need to swap out some more memory to gather space for opening a shell, on the other hand all other swapping processes must be stopped.)

If you tied such a command to a hot key then maybe you can use this as an emergency button saving you a lot a time. Any ideas if this is possible at all? Has somebody tried something like this before? If one could realize this it would be a cool feature :)