From: Matt Mackall <mpm@selenic.com>

We weren't merging freed blocks at the beginning of the free list.  Fixing
this showed a 2.5% efficiency improvement in a userspace test harness.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slob.c |    4 ++++
 1 file changed, 4 insertions(+)

diff -puN mm/slob.c~slob-fix-free-block-merging-at-head-of-subpage mm/slob.c
--- a/mm/slob.c~slob-fix-free-block-merging-at-head-of-subpage
+++ a/mm/slob.c
@@ -398,6 +398,10 @@ static void slob_free(void *block, int s
 	sp->units += units;
 
 	if (b < sp->free) {
+		if (b + units == sp->free) {
+			units += slob_units(sp->free);
+			sp->free = slob_next(sp->free);
+		}
 		set_slob(b, units, sp->free);
 		sp->free = b;
 	} else {
_