Re: [PATCH v3 33/33] Reimplement IDR and IDA using the radix tree

[Andrew Morton]

On Mon, 28 Nov 2016 13:50:37 -0800 Matthew Wilcox <mawilcox@xxxxxxxxxxxxxxxxx> wrote:

> The IDR is very similar to the radix tree.  It has some functionality
> that the radix tree did not have (alloc next free, cyclic allocation,
> a callback-based for_each, destroy tree), which is readily implementable
> on top of the radix tree.  A few small changes were needed in order to
> use a tag to represent nodes with free space below them.
> 
> The IDA is reimplemented as a client of the newly enhanced radix tree.
> As in the current implementation, it uses a bitmap at the last level of
> the tree.
> 
> Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> ---
>  include/linux/idr.h                     |  132 ++--
>  include/linux/radix-tree.h              |    5 +-
>  init/main.c                             |    3 +-
>  lib/idr.c                               | 1078 -------------------------------
>  lib/radix-tree.c                        |  632 ++++++++++++++++--

hm.  It's just a cosmetic issue, but perhaps the idr
wrappers-around-radix-tree code should be in a different .c file.



Before:

akpm3:/usr/src/25> size lib/idr.o lib/radix-tree.o  
   text    data     bss     dec     hex filename
   6566      89      16    6671    1a0f lib/idr.o
  11811     117       8   11936    2ea0 lib/radix-tree.o

After:

   text    data     bss     dec     hex filename
  14151     118       8   14277    37c5 lib/radix-tree.o


So 4500 bytes saved.  Decent.