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authorMel Gorman <mgorman@suse.de>2014-04-03 14:47:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-03 16:20:58 -0700
commitd26914d11751b23ca2e8747725f2cae10c2f2c1b (patch)
tree020b606fb9223e29292f54922a11111239e3a3f4 /mm/slub.c
parent91ca9186484809c57303b33778d841cc28f696ed (diff)
downloadop-kernel-dev-d26914d11751b23ca2e8747725f2cae10c2f2c1b.zip
op-kernel-dev-d26914d11751b23ca2e8747725f2cae10c2f2c1b.tar.gz
mm: optimize put_mems_allowed() usage
Since put_mems_allowed() is strictly optional, its a seqcount retry, we don't need to evaluate the function if the allocation was in fact successful, saving a smp_rmb some loads and comparisons on some relative fast-paths. Since the naming, get/put_mems_allowed() does suggest a mandatory pairing, rename the interface, as suggested by Mel, to resemble the seqcount interface. This gives us: read_mems_allowed_begin() and read_mems_allowed_retry(), where it is important to note that the return value of the latter call is inverted from its previous incarnation. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c16
1 files changed, 7 insertions, 9 deletions
diff --git a/mm/slub.c b/mm/slub.c
index 25f14ad..7611f14 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1684,7 +1684,7 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
return NULL;
do {
- cpuset_mems_cookie = get_mems_allowed();
+ cpuset_mems_cookie = read_mems_allowed_begin();
zonelist = node_zonelist(slab_node(), flags);
for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
struct kmem_cache_node *n;
@@ -1696,19 +1696,17 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
object = get_partial_node(s, n, c, flags);
if (object) {
/*
- * Return the object even if
- * put_mems_allowed indicated that
- * the cpuset mems_allowed was
- * updated in parallel. It's a
- * harmless race between the alloc
- * and the cpuset update.
+ * Don't check read_mems_allowed_retry()
+ * here - if mems_allowed was updated in
+ * parallel, that was a harmless race
+ * between allocation and the cpuset
+ * update
*/
- put_mems_allowed(cpuset_mems_cookie);
return object;
}
}
}
- } while (!put_mems_allowed(cpuset_mems_cookie));
+ } while (read_mems_allowed_retry(cpuset_mems_cookie));
#endif
return NULL;
}
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