From owner-freebsd-hackers@FreeBSD.ORG  Fri Dec  3 23:22:25 2010
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Date: Fri, 3 Dec 2010 22:56:31 +0000
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Subject: MADV_FREE and vm_page_dontneed()
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Is there a good reason why physical memory pages released by
madvise(...,MADV_FREE) get handled by vm_page_dontneed()?

vm_page_dontneed() leaves page that are already in the inactive queue
where they are, and otherwise distributes pages between the active
queue, and the inactive queue's tail and head in the ratio 1:3:28. That
seems reasonable for  MADV_DONTNEED, but MADV_FREE pages are from freed
dynamic memory, so passing them to vm_page_dontneed() leads to wasted
pages building-up in the active and inactive queues.

Wouldn't it make more sense to move all eligible MADV_FREE pages to the
head of the inactive queue?