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Re: [LSF/MM TOPIC] Using XArray to manage the VMA

On Wed, Mar 13, 2019 at 04:10:14PM +0100, Laurent Dufour wrote:
> If this is not too late and if there is still place available, I would like
> to attend the MM track and propose a topic about using the XArray to replace
> the VMA's RB tree and list.

If there isn't room on the schedule, then Laurent and I are definitely
going to sneak off and talk about this ourselves at some point.  Having a
high-bandwidth conversation about this is going to be really important
for us, and I think having other people involved would be good.

If there're still spots, it'd be good to have Liam Howlett join us.
He's doing the actual writing-of-code for the Maple Tree at the moment
(I did some earlier on, but recent commits are all him).

> Using the XArray in place of the VMA's tree and list seems to be a first
> step to the long way of removing/replacing the mmap_sem.
> However, there are still corner cases to address like the VMA splitting and
> merging which may raise some issue. Using the XArray's specifying locking
> would not be enough to handle the memory management, and additional fine
> grain locking like a per VMA one could be studied, leading to further
> discussion about the merging of the VMA.
> In addition, here are some topics I'm interested in:
> - Test cases to choose for demonstrating mm features or fixing mm bugs
> proposed by Balbir Singh
> - mm documentation proposed by Mike Rapoport
> Laurent.