SLUB: Avoid checking for a valid object before zeroing on the fastpath
The fastpath always results in a valid object. Move the check
for the NULL pointer to the slow branch that calls
__slab_alloc. Only __slab_alloc can return NULL if there is no
memory available.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
---
mm/slub.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2007-10-19 13:06:49.000000000 -0700
+++ linux-2.6/mm/slub.c 2007-10-19 13:08:30.000000000 -0700
@@ -1567,17 +1567,20 @@ static void __always_inline *slab_alloc(
local_irq_save(flags);
c = get_cpu_slab(s, smp_processor_id());
- if (unlikely(!c->freelist || !node_match(c, node)))
+ if (unlikely(!c->freelist || !node_match(c, node))) {
object = __slab_alloc(s, gfpflags, node, addr, c);
-
- else {
+ if (unlikely(!object)) {
+ local_irq_restore(flags);
+ return NULL;
+ }
+ } else {
object = c->freelist;
c->freelist = object[c->offset];
}
local_irq_restore(flags);
- if (unlikely((gfpflags & __GFP_ZERO) && object))
+ if (unlikely((gfpflags & __GFP_ZERO)))
memset(object, 0, c->objsize);
return object;