From: John Brooks <john.brooks@jolla.com>
Date: Tue, 24 Mar 2015 20:54:17 +0000 (-0400)
Subject: selinux: Use a better hash function for avtab
X-Git-Tag: omap-for-v4.1/fixes-rc1~139^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=33ebc1932a07efd8728975750409741940334489;p=pandora-kernel.git

selinux: Use a better hash function for avtab

This function, based on murmurhash3, has much better distribution than
the original. Using the current default of 2048 buckets, there are many
fewer collisions:

Before:
101421 entries and 2048/2048 buckets used, longest chain length 374
After:
101421 entries and 2048/2048 buckets used, longest chain length 81

The difference becomes much more significant when buckets are increased.
A naive attempt to expand the current function to larger outputs doesn't
yield any significant improvement; so this function is a prerequisite
for increasing the bucket size.

sds:  Adapted from the original patches for libsepol to the kernel.

Signed-off-by: John Brooks <john.brooks@jolla.com>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>
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