* We add ebitmap_for_each_positive_bit() which enables to walk on
any positive bit on the given ebitmap, to improve its performance
using common bit-operations defined in linux/bitops.h.
In the previous version, this logic was implemented using a combination
of ebitmap_for_each_bit() and ebitmap_node_get_bit(), but is was worse
in performance aspect.
This logic is most frequestly used to compute a new AVC entry,
so this patch can improve SELinux performance when AVC misses are happen.
* struct ebitmap_node is redefined as an array of "unsigned long", to get
suitable for using find_next_bit() which is fasted than iteration of
shift and logical operation, and to maximize memory usage allocated
from general purpose slab.
* Any ebitmap_for_each_bit() are repleced by the new implementation
in ss/service.c and ss/mls.c. Some of related implementation are
changed, however, there is no incompatibility with the previous
version.
* The width of any new line are less or equal than 80-chars.
The following benchmark shows the effect of this patch, when we
access many files which have different security context one after
another. The number is more than /selinux/avc/cache_threshold, so
any access always causes AVC misses.
selinux-2.6 selinux-2.6-ebitmap
AVG: 22.763 [s] 8.750 [s]
STD: 0.265 0.019
------------------------------------------
1st: 22.558 [s] 8.786 [s]
2nd: 22.458 [s] 8.750 [s]
3rd: 22.478 [s] 8.754 [s]
4th: 22.724 [s] 8.745 [s]
5th: 22.918 [s] 8.748 [s]
6th: 22.905 [s] 8.764 [s]
7th: 23.238 [s] 8.726 [s]
8th: 22.822 [s] 8.729 [s]
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
9fe79ad1e4