vm scenario tool / mincore(2) functionality for regular pages?

[bert hubert]

I'm building a tool to subject the VM to different scenarios and I'd like to
be able to determine if a page is swapped out or not. For a file I can
easily determine if a page is in memory (in the page cache) or not using the
mincore(2) system call.

I want to expand my tool so it can investigate which of its pages are
swapped out under cache pressure or real memory pressure.

However, to do this, I need a way to determine if a page is there or if it
is swapped out. My two questions are:

	1) is there an existing way to do this
	   (the kernel obviously knows)

	2) would it be correct to expand mincore to also work on
           non-filebacked memory so it works for 'swap-backed' memory too?

Thanks.

Some current output of the scenario tool:

vmloader> alloc 25
Arena now 25 megabytes, 6250 pages

vmloader> sweep
Sweeping from mbyte 0 to 25, 6250 pages. Done

vmloader> rusage
minor: 6250, major: 2, swaps: 0

vmloader> sweep 0 12
Sweeping from mbyte 0 to 12, 1440 pages. Done

vmloader> rusage
minor: 0, major: 0, swaps: 0

vmloader> touch
Touching from mbyte 0 to 25, 6250 pages. Done

vmloader> rusage
minor: 6249, major: 0, swaps: 0

vmloader> rsweep
Random sweeping from mbyte 0 to 25, 6250 pages. Done

vmloader> rusage
minor: 0, major: 0, swaps: 0

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