Re: [PATCH RFC 00/12] mm/vmalloc: migrate vmap_area indexing from rb-tree to maple-tree

[Matthew Wilcox]

On Sat, Jun 13, 2026 at 10:49:42PM +0530, Pranjal Arya wrote:
> vmalloc's free/busy/lazy area tracking is one of the last remaining
> augmented-rb_tree consumers in the core mm allocators. The rest of
> mm/ has been gradually consolidating range-keyed indexing around
> maple_tree (notably the per-process VMA tree in mm/mmap.c), and
> the underlying reason is a structural mismatch between rb_tree and
> range tracking:

First, and most importantly, I love this.  The maple tree is undoubtedly
the right data structure to use for this purpose.

What I don't understand is why you maintain a separate "free" tree.
It should not be necessary any more, but maybe you tried removing it
already and found a performance problem?