- Add a new function uma_zone_exhausted() to see if a zone is full.

- Add a printf in swp_pager_meta_build() to warn if the swapzone becomes
  exhausted so that there's at least a warning before a box that runs out
  of swapzone space before running out of swap space deadlocks.

MFC after:	1 week
Reviwed by:	alc

3 files changed, 25 insertions, 0 deletions

diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
index 7b7e5d1..46f49d2 100644
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -1746,6 +1746,8 @@ retry:
 		if (swap == NULL) {
 			mtx_unlock(&swhash_mtx);
 			VM_OBJECT_UNLOCK(object);
+			if (uma_zone_exhausted(swap_zone))
+				printf("swap zone exhausted, increase kern.maxswzone\n");
 			VM_WAIT;
 			VM_OBJECT_LOCK(object);
 			goto retry;
diff --git a/sys/vm/uma.h b/sys/vm/uma.h
index 2181ec7..08a55d6 100644
--- a/sys/vm/uma.h
+++ b/sys/vm/uma.h
@@ -509,6 +509,17 @@ void uma_prealloc(uma_zone_t zone, int itemcnt);
 u_int32_t *uma_find_refcnt(uma_zone_t zone, void *item);
 
 /*
+ * Used to determine if a fixed-size zone is exhausted.
+ *
+ * Arguments:
+ *	zone    The zone to check
+ *
+ * Returns:
+ * 	Non-zero if zone is exhausted.
+ */
+int uma_zone_exhausted(uma_zone_t zone);
+
+/*
  * Exported statistics structures to be used by user space monitoring tools.
  * Statistics stream consusts of a uma_stream_header, followed by a series of
  * alternative uma_type_header and uma_type_stat structures.  Statistics
diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
index 3e8bb2e..ac3ffc4 100644
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -2681,6 +2681,18 @@ uma_reclaim(void)
 	bucket_zone_drain();
 }
 
+/* See uma.h */
+int
+uma_zone_exhausted(uma_zone_t zone)
+{
+	int full;
+
+	ZONE_LOCK(zone);
+	full = (zone->uz_keg->uk_flags & UMA_ZFLAG_FULL);
+	ZONE_UNLOCK(zone);
+	return (full);	
+}
+
 void *
 uma_large_malloc(int size, int wait)
 {