Commit 424251a4 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds

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.comSigned-off-by: default avatarMatthew Wilcox <willy@linux.intel.com>
Tested-by: default avatarKirill 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 44430612
......@@ -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)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment