[openib-general] kernel VM monitor for memory registration caching

[Muli Ben-Yehuda]

On Mon, Aug 01, 2005 at 06:04:27PM +0300, Gleb Natapov wrote:

> I don't like the idea of splitting VMAs if we can manage without it. You'll 
> end up having to many of them.

... or you end up duplicating the VMA functionality on a sub-vma
level. Consider:

You have a single vma with some number of pages, where some random
pages are registered and some aren't. You need to be able to check for
a given page whetehr it's registered or not, so you build some data
structure based on the stard and end address (or page, or whatever),
so that you can check if a given address is within a registered
page. But this is exactly the sort of thing that the VMA level is
built for: use the red black tree to find the vma for a given address,
then check if the vma is registered.

Linux can already cope with a large number  of vma's, I think that a
solution that does not split vma's will end up with either artificial
limitations (can't have more than two different regions within a vma)
or reimplementing vma layer functionality. Of course, I could be
completely wrong :-)

Cheers,
Muli
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/