Evgeniy Polyakov [off-list ref] writes:

Design notes.
Original idea was to store meta information used for allocation in an
AVL tree [1], but since I found a way to use some "unused" fields in struct page,
tree is unused in the allocator.

But there seems to be still an AVL tree in there?

Benchmarks with trivial epoll based web server showed noticeble (more
than 40%) imrovements of the request rates (1600-1800 requests per
second vs. more than 2300 ones). It can be described by more
cache-friendly freeing algorithm, by tighter objects packing and thus
reduced cache line ping-pongs, reduced lookups into higher-layer caches
and so on.

So what are its drawbacks compared to slab/kmalloc? 

Also if it really performs that much better it might be a good
idea to replace all of kmalloc() with it, but doing that
would require a lot more benchmarks with various workloads
and small and big machines first.

-Andi