Multiple page support

Rao, Nikhil nikhil.rao at
Mon Aug 18 21:11:59 UTC 2008

What is the current status of multiple page sizes for applications (4K
and 2MB) in FreeBSD 8-CURRENT ? It is enabled by default for the amd64
arch and only available in the amd64 and i386 architectures.

>From reading the source code, there is support for "reservations" as
described in the original paper

Is the feature implementation complete apart from bug fixes etc ? Couple
of features that I am referring to 

1) I haven't seen any code for the "population map" radix tree that is
supposed to help with reservation preemption (It enables you to lazily
update the reservation pointer in struct vm_page, but this pointer
itself doesn't exist anyways)

2) The original paper describes modification to the paging daemon to
handle fragmentation, are these modifications implemented ?

3) Say the hardware were able to support an additional page size, How
easy would it be to add an additional page size ? 


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