Re: anon_vma RFC2

[Rajesh Venkatasubramanian]

> prio_tree can only sit on top of anon_vma, not on top of
> anonmm+linus-unshare-mremap (and yes, I cannot share
> vma.shared.prio_tree_node) but pratically it's not needed for the
> anon_vmas.

Agreed. prio_tree is only useful for anon_vma. But, after
linus-unshare-mremap, the anon_vma patch can be modified
(simplified ?) a lot. You don't need any as.anon_vma, as.vma
pointers in the page struct. You just need the already existing
page->mapping and page->index, and a prio_tree of all anon vmas.
The prio_tree can be used to get to the "interesting vmas" without
walking all mms. However, the new prio_tree node adds 16 bytes
per-vma. Considering there may not be much sharing of anon vmas
in common case, I am not sure whether that is worthwhile. Maybe
we can wait for someone to write a program that locks the machine :)

Rajesh


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