tree ef17a945288c333c345643325783f374e10a4020
parent 5bf54a9758c230d9e957e7b4f3a41c226660dd49
author Jesse Gross <jesse@nicira.com> 1306452302 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1306455153 -0700

flex_array: avoid divisions when accessing elements

On most architectures division is an expensive operation and accessing an
element currently requires four of them.  This performance penalty
effectively precludes flex arrays from being used on any kind of fast
path.  However, two of these divisions can be handled at creation time and
the others can be replaced by a reciprocal divide, completely avoiding
real divisions on access.

[eparis@redhat.com: rebase on top of changes to support 0 len elements]
[eparis@redhat.com: initialize part_nr when array fits entirely in base]
Signed-off-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>