Re: [PATCH v3 00/15] Free user PTE page table pages

[Jason Gunthorpe]

On Wed, Nov 10, 2021 at 06:37:46PM +0100, David Hildenbrand wrote:

> It will be if we somewhat frequent when reclaim an empty PTE page table
> as soon as it turns empty.

What do you think is the frequency of unlocked page table walks that
this would have to block on?

> Also, it adds complexity for something that is only a problem in some
> corner cases -- sparse memory mappings, especially relevant for some
> memory allocators after freeing a lot of memory or running VMs with
> memory ballooning after inflating the balloon. Some of these use cases
> might be good with just triggering page table reclaim manually from user
> space.

Right, this is why it would be nice if the complexity could address
more than one problem, like the existing complex locking around the
thp stuff..

Jason