If you don't have any swap, or if you run out of swap, the major
difference between 2.2.x and 2.4.x is probably going to be the oom
handling: I suspect that 2.4.x might be more likely to kill things off
sooner (but it tries to be graceful about which processes to kill).

Not having any swap is going to be a performance issue for both 2.2.x and
2.4.x - Linux likes to push inactive dirty pages out to swap where they
can lie around without bothering anybody, even if there is no _major_
memory crunch going on.

If you do have swap, but it's smaller than your available physical RAM, I
suspect that the Linux-2.4 swap pre-allocate may cause that kind of
performance degradation earlier than 2.2.x would have. Another way of
putting this: in 2.2.x you could use a fairly small swap partition to pick
up some of the slack, and in 2.4.x a really small swap-partition doesn't
really buy you much anything.

Yes, that kind of swap size tuning will still work in 2.4.x, but the sizes
you tune for would be different, I'm afraid. If you have, say, 128MB or
RAM, and you used to make a smallish partition of 64MB for "slop" in
2.2.x, I really suspect that you might like to increase it to 128MB or
196MB.

Of course, if you really only used your swap for "slop", I don't think
you'll necessarily notice the difference.

NOTE! The above guide-lines are pure guesses. The machines I use have had
big swap-partitions or none at all, so I think we'll just have to wait and
see.

                        Linus

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