Make deactivation occur implicitly while checking out the current freelist.
This avoids one cmpxchg operation on a slab that is now fully in use.
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
---
include/linux/slub_def.h | 1 +
mm/slub.c | 21 +++++++++++++++++++--
2 files changed, 20 insertions(+), 2 deletions(-)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2011-05-16 12:51:49.901458516 -0500
+++ linux-2.6/mm/slub.c 2011-05-16 12:51:57.171458507 -0500
@@ -1963,9 +1963,21 @@ static void *__slab_alloc(struct kmem_ca
object = page->freelist;
counters = page->counters;
new.counters = counters;
- new.inuse = page->objects;
VM_BUG_ON(!new.frozen);
+ /*
+ * If there is no object left then we use this loop to
+ * deactivate the slab which is simple since no objects
+ * are left in the slab and therefore we do not need to
+ * put the page back onto the partial list.
+ *
+ * If there are objects left then we retrieve them
+ * and use them to refill the per cpu queue.
+ */
+
+ new.inuse = page->objects;
+ new.frozen = object != NULL;
+
} while (!cmpxchg_double_slab(s, page,
object, counters,
NULL, new.counters,
@@ -1974,8 +1986,11 @@ static void *__slab_alloc(struct kmem_ca
load_freelist:
VM_BUG_ON(!page->frozen);
- if (unlikely(!object))
+ if (unlikely(!object)) {
+ c->page = NULL;
+ stat(s, DEACTIVATE_BYPASS);
goto new_slab;
+ }
stat(s, ALLOC_REFILL);
@@ -4659,6 +4674,7 @@ STAT_ATTR(DEACTIVATE_EMPTY, deactivate_e
STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head);
STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail);
STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees);
+STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);
STAT_ATTR(ORDER_FALLBACK, order_fallback);
STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);
STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
@@ -4719,6 +4735,7 @@ static struct attribute *slab_attrs[] =
&deactivate_to_head_attr.attr,
&deactivate_to_tail_attr.attr,
&deactivate_remote_frees_attr.attr,
+ &deactivate_bypass_attr.attr,
&order_fallback_attr.attr,
&cmpxchg_double_fail_attr.attr,
&cmpxchg_double_cpu_fail_attr.attr,
Index: linux-2.6/include/linux/slub_def.h
===================================================================
--- linux-2.6.orig/include/linux/slub_def.h 2011-05-16 12:51:49.901458516 -0500
+++ linux-2.6/include/linux/slub_def.h 2011-05-16 12:51:57.171458507 -0500
@@ -32,6 +32,7 @@ enum stat_item {
DEACTIVATE_TO_HEAD, /* Cpu slab was moved to the head of partials */
DEACTIVATE_TO_TAIL, /* Cpu slab was moved to the tail of partials */
DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */
+ DEACTIVATE_BYPASS, /* Implicit deactivation */
ORDER_FALLBACK, /* Number of times fallback was necessary */
CMPXCHG_DOUBLE_CPU_FAIL,/* Failure of this_cpu_cmpxchg_double */
CMPXCHG_DOUBLE_FAIL, /* Number of times that cmpxchg double did not match */
--
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