Re: [PATCH v4] drivers/base/memory.c: cache blocks in radix tree to accelerate lookup

David Hildenbrand
2020-01-15T19:09:59Z

On 09.01.20 22:25, Scott Cheloha wrote:
> Searching for a particular memory block by id is an O(n) operation
> because each memory block's underlying device is kept in an unsorted
> linked list on the subsystem bus.
>
> We can cut the lookup cost to O(log n) if we cache the memory blocks in
> a radix tree. With a radix tree cache in place both memory subsystem
> initialization and memory hotplug run palpably faster on systems with a
> large number of memory blocks.
>
> Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Acked-by: Nathan Lynch <nathanl@linux.ibm.com>
> Acked-by: Michal Hocko <mhocko@suse.com>

Soooo,

I just learned that radix trees are nowadays only a wrapper for xarray
(for quite a while already!), and that the xarray interface shall be
used in new code.

include/linux/radix-tree.h:

/* Keep unconverted code working */
#define radix_tree_root xarray
[...]

Do we want to convert this code before sending it to Linus'? (resend
this patch, or a fixup on top)

--
Thanks,

David / dhildenb