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| author | Eric Dumazet <dada1@cosmosbay.com> | 2006-03-25 03:08:19 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-25 08:23:01 -0800 |
| commit | d74beb9f33a5f16d2965f11b275e401f225c949d (patch) | |
| tree | 48f851753ebe9c9c8dd701dcdd0c5e1d7c629579 | |
| parent | 34f361ade2fb4a869f6a7714d01c04ce4cfa75d9 (diff) | |
| download | lwn-d74beb9f33a5f16d2965f11b275e401f225c949d.tar.gz lwn-d74beb9f33a5f16d2965f11b275e401f225c949d.zip | |
[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>
| -rw-r--r-- | kernel/sys.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index 119fb0d9e24e..38bc73ede2ba 100644 --- 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; |