Actively limit the allocation of mbufs to NMBUFS/nmbufs and mbuf clusters

to NMBCLUSTERS/nmbclusters/kern.ipc.nmbclusters.

Add a read-only sysctl kern.ipc.nmbufs matching kern.ipc.nmbclusters.

Submitted by:	Bosko Milekic <bmilekic@dsuper.net>

1 files changed, 22 insertions, 2 deletions

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index 8c3c4bf..cc38c40 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -81,12 +81,14 @@ SYSCTL_INT(_kern_ipc, OID_AUTO, mbuf_wait, CTLFLAG_RW,
 	   &mbuf_wait, 0, "");
 SYSCTL_STRUCT(_kern_ipc, KIPC_MBSTAT, mbstat, CTLFLAG_RW, &mbstat, mbstat, "");
 SYSCTL_INT(_kern_ipc, KIPC_NMBCLUSTERS, nmbclusters, CTLFLAG_RD, 
-	   &nmbclusters, 0, "Maximum number of mbuf clusters avaliable");
+	   &nmbclusters, 0, "Maximum number of mbuf clusters available");
+SYSCTL_INT(_kern_ipc, OID_AUTO, nmbufs, CTLFLAG_RD, &nmbufs, 0,
+	   "Maximum number of mbufs available"); 
 #ifndef NMBCLUSTERS
 #define NMBCLUSTERS	(512 + MAXUSERS * 16)
 #endif
 TUNABLE_INT_DECL("kern.ipc.nmbclusters", NMBCLUSTERS, nmbclusters);
-TUNABLE_INT_DECL("kern.ipc.nmbufs", NMBCLUSTERS * 4, nmbufs);	/* XXX fixup? */
+TUNABLE_INT_DECL("kern.ipc.nmbufs", NMBCLUSTERS * 4, nmbufs);
 
 static void	m_reclaim __P((void));
 
@@ -141,6 +143,14 @@ m_mballoc(nmb, how)
 	int nbytes;
 
 	/*
+	 * If we've hit the mbuf limit, stop allocating from mb_map,
+	 * (or trying to) in order to avoid dipping into the section of
+	 * mb_map which we've "reserved" for clusters.
+	 */
+	if ((nmb + mbstat.m_mbufs) > nmbufs)
+		return (0);
+
+	/*
 	 * Once we run out of map space, it will be impossible to get
 	 * any more (nothing is ever freed back to the map)
 	 * -- however you are not dead as m_reclaim might
@@ -267,6 +277,16 @@ m_clalloc(ncl, how)
 	int npg;
 
 	/*
+	 * If we've hit the mcluster number limit, stop allocating from
+	 * mb_map, (or trying to) in order to avoid dipping into the section
+	 * of mb_map which we've "reserved" for mbufs.
+	 */
+	if ((ncl + mbstat.m_clusters) > nmbclusters) {
+		mbstat.m_drops++;
+		return (0);
+	}
+
+	/*
 	 * Once we run out of map space, it will be impossible
 	 * to get any more (nothing is ever freed back to the
 	 * map). From this point on, we solely rely on freed