Hi,

This is a patch with page ageing for 2.4.0-test4-pre1.

Performance, unoptimized filesystem:
* streamed write is as good as 2.2.14
* streamed copy is 3/4 of 2.2.14
* streamed read is close to 2.2.14

Potential problems:
* Got a BUG mm.h:321 while running this patch,
  unrelated? (more about this in another email)
  

Features:
* does NOT add any field in page structure.
* round robin lists is used to simulate ageing.
* referenced pages are moved 2 steps forward.
* multi used paged are moved 4 steps forward.
* non free able, tryagain, are moved 1 steps forward.
* new pages are inserted 3 steps forward.
* no pages are moved backward or to currently scanned.
and new in this release:
* pages failing zone test are moved to a list per zone.
  This lists are searched first!
* removed one unnecessary cause for SetPageReferenced


Future work:
* trim offsets / size / priority
* remove code that unnecessary sets page as referenced (Riel?)
* split pagemap_lru_lock (if wanted on SMP)
* move pages of zones with pressure less forward...
* ...
additional idea:
* periodically check pages for referenced - move forward.

/RogerL


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