diff options
| author | Matthew Wilcox <willy@linux.intel.com> | 2016-12-14 15:09:22 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-12-14 16:04:10 -0800 |
| commit | 424251a4a929a1b6dff2056d49135e3805132e32 (patch) | |
| tree | 191e913288fe1c45d64e93e5715e00fd47221457 /include/linux/idr.h | |
| parent | 444306129a920015a2cc876d13fcbf52382f39bd (diff) | |
| download | lwn-424251a4a929a1b6dff2056d49135e3805132e32.tar.gz lwn-424251a4a929a1b6dff2056d49135e3805132e32.zip | |
idr: reduce the number of bits per level from 8 to 6
In preparation for merging the IDR and radix tree, reduce the fanout at
each level from 256 to 64. If this causes a performance problem then a
bisect will point to this commit, and we'll have a better idea about
what we might do to fix it.
Link: http://lkml.kernel.org/r/1480369871-5271-66-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/idr.h')
| -rw-r--r-- | include/linux/idr.h | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/include/linux/idr.h b/include/linux/idr.h index 1eb755f77f2f..3c01b89aed67 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -18,12 +18,11 @@ #include <linux/rcupdate.h> /* - * We want shallower trees and thus more bits covered at each layer. 8 - * bits gives us large enough first layer for most use cases and maximum - * tree depth of 4. Each idr_layer is slightly larger than 2k on 64bit and - * 1k on 32bit. + * Using 6 bits at each layer allows us to allocate 7 layers out of each page. + * 8 bits only gave us 3 layers out of every pair of pages, which is less + * efficient except for trees with a largest element between 192-255 inclusive. */ -#define IDR_BITS 8 +#define IDR_BITS 6 #define IDR_SIZE (1 << IDR_BITS) #define IDR_MASK ((1 << IDR_BITS)-1) |