Commit d74beb9f authored Mar 25, 2006 by Eric Dumazet Committed by Linus Torvalds Mar 25, 2006

[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>

parent 34f361ad

kernel/sys.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;