[viraptor]

I feel like the real metric is like to see from swap usage is: how much time did I spend waiting to swap-in a page, how much extra cache pages it gave me, and what's the cache hit ratio. If the big purpose is to allow those extra few pages to be available, then either it's worth doing or not - there should be an objective way to look at this. Unfortunately only the second and third part is easily available. The first... maybe via systemtap?

[cdown]

> how much time did I spend waiting to swap-in a page

You can do this with eBPF/BCC by using funclatency (https://github.com/iovisor/bcc/blob/master/tools/funclatency...) to trace swap related kernel calls. It depends on exactly what you want, but take a look at mm/swap.c and you'll probably find a function which results in the semantics you want.