Questions about the zoned page frame allocator and fix mapped addresses

[Valdis.Kletnieks at vt.edu]

On Mon, 30 Mar 2015 20:25:38 +0530, Sunny Shah said:

>    - The book says, about releasing page frames to the per CPU cache - "no
>    page frame is ever released to the cold cache: the kernel always assumes
>    the freed page frame is hot with respect to the hardware cache". What is
>    the reason for this decision ?

What can go wrong if the page is cold but the kernel assumes it's hot?

What can go wrong if the kernel assumes it's cold but it's actually hot?

(Hint - in which cases will it do a cache flush?  In which cases is a
cache flush needed? What happens in each case if the kernel guesses wrong?)
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