Re: NVFS XFS metadata (was: [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache)

[Matthew Wilcox]

On Mon, Sep 21, 2020 at 12:20:42PM -0400, Mikulas Patocka wrote:
> The same for directories - NVFS hashes the file name and uses radix-tree 
> to locate a directory page where the directory entry is located. XFS 
> b+trees would result in much more accesses than the radix-tree.

What?  Radix trees behave _horribly_ badly when indexed by a hash.
If you have a 64-bit hash and use 8 bits per level of the tree, you have
to traverse 8 pointers to get to your destination.  You might as well
use a linked list!