2013/2/19 Soham Chakraborty [off-list ref]:

Hey dude,

Apologies for this kind of approach but I was not sure whether I can
directly mail the list with such a noobish question. I have been poking
around in mm subsystem for around 2 years now and I have never got a fine,
bullet proof answer to this question.

Why would something swap even if there is free or cached memory available.

It's known that swap operation is done with memory reclaiming.There
are three occasions for memory reclaiming: low on memory reclaiming,
Hibernation reclaiming, periodic reclaiming.

For periodic reclaiming, some page may be swapped out even if there is
free or cached memory available.

Please correct me if my understanding is wrong.

Regards,
Haifeng Li

I have read about all possible theories including lru algorithm,
vm.swappiness, kernel heuristics, overcommit of memory and all. But I for
the heck of me, can't understand what is the issue. And I can't make the end
users satisfied too. I keep blabbering kernel heuristics too much.

Do you have any answer to this question. If you think this is worthy of
going to list, I will surely do so.

Soham