[merged] idr-reduce-the-number-of-bits-per-level-from-8-to-6.patch removed from -mm tree

[merged] idr-reduce-the-number-of-bits-per-level-from-8-to-6.patch removed from -mm tree

[akpm]

The patch titled
     Subject: idr: reduce the number of bits per level from 8 to 6
has been removed from the -mm tree.  Its filename was
     idr-reduce-the-number-of-bits-per-level-from-8-to-6.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------
From: Matthew Wilcox <willy@linux.intel.com>
Subject: 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>
---

 include/linux/idr.h |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff -puN include/linux/idr.h~idr-reduce-the-number-of-bits-per-level-from-8-to-6 include/linux/idr.h
--- a/include/linux/idr.h~idr-reduce-the-number-of-bits-per-level-from-8-to-6
+++ a/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)
 
_

Patches currently in -mm which might be from willy@linux.intel.com are

reimplement-idr-and-ida-using-the-radix-tree.patch