Re: questions about LRU

[Roger Larsson <roger.larsson@norran.net>]

On Saturday 18 November 2000 00:02, Min San Co wrote:
> Hi!
>
> I am trying to implement the LRU page replacement scheme (Least-Recently
> Used).  My idea is to what create a queue that contains pointers to every
> page held by every process in the system.  This queue should be sorted to
> reflect the most recently used pages, which should be at the front.  I am
> thinking of manipulating this list on every timer interrupt (ie 10 msec).

pages are already placed in a ring using the page struct field lru(!)

> After every interrupt, the ordering of pages on the queue will be updated
> based on what pages have been accessed since the last timer interrupt.  I
> am thinking of using the reference bit to determine which page has been
> accessed since the last timer interrupt.  The pages that have been recently
> used will be moved to the front of the queue.

This will not scale - think about 64GB machines... You would need to scan all
pages every timer interrupt...

>
> Any ideas on where to put the queue?
>
Use the existing queues - like active_list (introduced in 2.4.0-test9)
It is scanned but slower than you suggest...

> Cheers!
>
> Max C.
>
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