From 8db049b3d666b3676ff4a976e03c14de302bf9fa Mon Sep 17 00:00:00 2001 From: "Raphael S. Carvalho" Date: Tue, 30 Apr 2013 15:28:26 -0700 Subject: [PATCH] kernel/pid.c: improve flow of a loop inside alloc_pidmap. find_next_offset() searches for an available "cleaned bit" in the respective pid bitmap (page), so returns the offset if found, otherwise it returns a value equals to BITS_PER_PAGE. For example, suppose find_next_offset didn't find any available bit, so there's no purpose to call mk_pid (Wasteful Cpu Cycles). Therefore, I found it could be better to call mk_pid after the checking (offset < BITS_PER_PAGE) returned sucessfully! Another point: If (offset < BITS_PER_PAGE) results in a "failure", then mk_pid would be called again afterwards. [akpm@linux-foundation.org: simplify code] Signed-off-by: Raphael S. Carvalho Cc: "Eric W. Biederman" Cc: Serge Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/pid.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/pid.c b/kernel/pid.c index 047dc62..8147bdf 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -183,15 +183,19 @@ static int alloc_pidmap(struct pid_namespace *pid_ns) break; } if (likely(atomic_read(&map->nr_free))) { - do { + for ( ; ; ) { if (!test_and_set_bit(offset, map->page)) { atomic_dec(&map->nr_free); set_last_pid(pid_ns, last, pid); return pid; } offset = find_next_offset(map, offset); + if (offset >= BITS_PER_PAGE) + break; pid = mk_pid(pid_ns, map, offset); - } while (offset < BITS_PER_PAGE && pid < pid_max); + if (pid >= pid_max) + break; + } } if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) { ++map; -- 2.7.4