- Simplify implementation of uma_zone_get_max.

- Add uma_zone_get_cur which returns the current approximate occupancy of
  a zone. This is useful for providing stats via sysctl amongst other things.

Sponsored by:	FreeBSD Foundation
Reviewed by:	gnn, jhb
MFC after:	2 weeks

2 files changed, 35 insertions, 4 deletions

diff --git a/sys/vm/uma.h b/sys/vm/uma.h
index f0522b0..6ab515e 100644
--- a/sys/vm/uma.h
+++ b/sys/vm/uma.h
@@ -471,6 +471,17 @@ void uma_zone_set_max(uma_zone_t zone, int nitems);
 int uma_zone_get_max(uma_zone_t zone);
 
 /*
+ * Obtains the approximate current number of items allocated from a zone
+ *
+ * Arguments:
+ *	zone  The zone to obtain the current allocation count from
+ *
+ * Return:
+ *	int  The approximate current number of items allocated from the zone
+ */
+int uma_zone_get_cur(uma_zone_t zone);
+
+/*
  * The following two routines (uma_zone_set_init/fini)
  * are used to set the backend init/fini pair which acts on an
  * object as it becomes allocated and is placed in a slab within
diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
index 23b88ee..94b12e5 100644
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -2805,16 +2805,36 @@ uma_zone_get_max(uma_zone_t zone)
 
 	ZONE_LOCK(zone);
 	keg = zone_first_keg(zone);
-	if (keg->uk_maxpages)
-		nitems = keg->uk_maxpages * keg->uk_ipers;
-	else
-		nitems = 0;
+	nitems = keg->uk_maxpages * keg->uk_ipers;
 	ZONE_UNLOCK(zone);
 
 	return (nitems);
 }
 
 /* See uma.h */
+int
+uma_zone_get_cur(uma_zone_t zone)
+{
+	int64_t nitems;
+	u_int i;
+
+	ZONE_LOCK(zone);
+	nitems = zone->uz_allocs - zone->uz_frees;
+	CPU_FOREACH(i) {
+		/*
+		 * See the comment in sysctl_vm_zone_stats() regarding the
+		 * safety of accessing the per-cpu caches. With the zone lock
+		 * held, it is safe, but can potentially result in stale data.
+		 */
+		nitems += zone->uz_cpu[i].uc_allocs -
+		    zone->uz_cpu[i].uc_frees;
+	}
+	ZONE_UNLOCK(zone);
+
+	return (nitems < 0 ? 0 : nitems);
+}
+
+/* See uma.h */
 void
 uma_zone_set_init(uma_zone_t zone, uma_init uminit)
 {