tree 21b3395270516a4978b10090fe8d9bd4bce8203b
parent 38e880540f983045da7a00fbc50daad238207fc5
author richard kennedy <richard@rsk.demon.co.uk> 1307443592 +0000
committer Chris Mason <chris.mason@oracle.com> 1307746630 -0400

btrfs: remove 64bit alignment padding to allow extent_buffer to fit into one fewer cacheline

Reorder extent_buffer to remove 8 bytes of alignment padding on 64 bit
builds. This shrinks its size to 128 bytes allowing it to fit into one
fewer cache lines and allows more objects per slab in its kmem_cache.

slabinfo extent_buffer reports :-

 before:-
    Sizes (bytes)     Slabs
    ----------------------------------
    Object :     136  Total  :     123
    SlabObj:     136  Full   :     121
    SlabSiz:    4096  Partial:       0
    Loss   :       0  CpuSlab:       2
    Align  :       8  Objects:      30

 after :-
    Object :     128  Total  :       4
    SlabObj:     128  Full   :       2
    SlabSiz:    4096  Partial:       0
    Loss   :       0  CpuSlab:       2
    Align  :       8  Objects:      32

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Chris Mason <chris.mason@oracle.com>