[radisb]

Assuming that OP is correct in everything, it isn't shown anywhere that swap must reside in persistent storage. It could be stored in RAM, couldn't it? I mean you always have a fixed max amount of swap, so if it fits in memory , then why not put it in memory? But then why bother with swap?

[KaiserPro]

> then why not put it in memory? But then why bother with swap?

because ram is expensive compared to disk.

Ram is normally fixed compared to disk

by storing not-used but still needed pages on disk, allows for much greater performance with less resources. for example it allows a bigger VFS cache.

[radisb]

So hypothetically, if ram was as cheap and easy to add as storage, swap would not make sense?

[KaiserPro]

depending on OS and upper limit, yeah RAM all the way. But I suspect the kernel doesn't think like that. I know that OSX does things differently, so perhaps there are better ways

[rwmj]

It can be, that's what zswap is all about.