Why active list and inactive list?

[Niki Hammler <mailinglists@nobaq.net>]

Dear Linux Developers/Enthusiasts,

For a course at my university I'm implementing parts of an operating
system where I get most ideas from the Linux Kernel (which I like very
much). One book I gain information from is [1].

Linux uses for its Page Replacing Algorithm (based on LRU) *two* chained
lists - one active list and one active list.
I implemented my PRA this way too.

No the big question is: WHY do I need *two* lists? Isn't it just
overhead/more work? Are there any reasons for that?

In my opinion, it would be better to have just one just; pop frames to
be swapped out from the end of the list and push new frames in front of
it. Then just evaluate the frames and shift them around in the list.

Is there any explanation why Linux uses two lists?

Thanks you very much in advance!

Best regards,
Niki



[1] Linux Kernelarchitektur. Konzepte, Strukturen und Algorithmen von
Kernel 2.6. Wolfang Mauerer, Hanser, ISBN 3-446-22566-8