[PATCH] Use unsigned int types for a faster bsearch

This patch avoids arithmetic on 'signed' types that are slower than
'unsigned'.  This saves space and cpu cycles.

size of kernel/sys.o before the patch (gcc-3.4.5)

    text    data     bss     dec     hex filename
   10924     252       4   11180    2bac kernel/sys.o

size of kernel/sys.o after the patch
    text    data     bss     dec     hex filename
   10903     252       4   11159    2b97 kernel/sys.o

I noticed that gcc-4.1.0 (from Fedora Core 5) even uses idiv instruction for
(a+b)/2 if a and b are signed.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/sys.c b/kernel/sys.c
index 119fb0d..38bc73e 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1363,7 +1363,7 @@ static void groups_sort(struct group_info *group_info)
 /* a simple bsearch */
 int groups_search(struct group_info *group_info, gid_t grp)
 {
-       int left, right;
+       unsigned int left, right;
 
        if (!group_info)
                return 0;
@@ -1371,7 +1371,7 @@ int groups_search(struct group_info *group_info, gid_t grp)
        left = 0;
        right = group_info->ngroups;
        while (left < right) {
-               int mid = (left+right)/2;
+               unsigned int mid = (left+right)/2;
                int cmp = grp - GROUP_AT(group_info, mid);
                if (cmp > 0)
                        left = mid + 1;