diff options
author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2014-08-06 16:09:44 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-06 18:01:25 -0700 |
commit | 61b3d6c48f059bb054b0019088736dab6c2ac0ec (patch) | |
tree | 0d312d70673c63c8e02fcdd7c690e0e67e57922f /lib | |
parent | 694123031d12458a343492528fa40113e5ec843e (diff) |
lib: list_sort.c: Limit number of unused cmp callbacks
The helper merge_and_restore_back_links() makes sure to call the
caller's cmp function during the final ->prev pointer fixup, so that the
cmp function may call cond_resched(). However, if the cmp function does
not call cond_resched() at all, this is entirely redundant. If it does,
doing at least two function calls for every two pointer assignments is a
bit excessive. This patch limits the calls to once for every 256
iterations.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Don Mullis <don.mullis@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/list_sort.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/lib/list_sort.c b/lib/list_sort.c index a34c78c30d5..6b9fdaf1d32 100644 --- a/lib/list_sort.c +++ b/lib/list_sort.c @@ -47,6 +47,7 @@ static void merge_and_restore_back_links(void *priv, struct list_head *a, struct list_head *b) { struct list_head *tail = head; + u8 count = 0; while (a && b) { /* if equal, take 'a' -- important for sort stability */ @@ -70,7 +71,8 @@ static void merge_and_restore_back_links(void *priv, * element comparison is needed, so the client's cmp() * routine can invoke cond_resched() periodically. */ - (*cmp)(priv, tail->next, tail->next); + if (unlikely(!(++count))) + (*cmp)(priv, tail->next, tail->next); tail->next->prev = tail; tail = tail->next; |