Add two loader tuneables that allow one to change the maximum number of

queue items that can be allocated by netgraph and the number of free queue
items that are cached on a private list.

Netgraph places an upper limit on the number of queue items it may allocate.
When there is a large number of netgraph messages travelling through the
system (100k/sec and more) there is a high probability, that messages get
queued at the nodes and netgraph runs out of queue items. In this case the data
flow through netgraph gets blocked. The tuneable for the number of free
items lets one trade memory for performance.

The tunables are also available as read-only sysctls.

PR:		kern/47393
Reviewed by:	julian
Approved by:	jake (mentor)

1 files changed, 11 insertions, 1 deletions

diff --git a/sys/netgraph/ng_base.c b/sys/netgraph/ng_base.c
index eb5a8eb..4c8dde3 100644
--- a/sys/netgraph/ng_base.c
+++ b/sys/netgraph/ng_base.c
@@ -3017,8 +3017,18 @@ SYSCTL_INT(_net_graph, OID_AUTO, msg_version, CTLFLAG_RD, 0, NG_VERSION, "");
 
 
 static int			allocated;	/* number of items malloc'd */
+
 static int			maxalloc = 128;	/* limit the damage of a leak */
-static const int		ngqfreemax = 64;/* cache at most this many */
+static int			ngqfreemax = 64;/* cache at most this many */
+
+TUNABLE_INT("net.graph.maxalloc", &maxalloc);
+SYSCTL_INT(_net_graph, OID_AUTO, maxalloc, CTLFLAG_RD, &maxalloc,
+    0, "Maximum number of queue items to allocate");
+
+TUNABLE_INT("net.graph.ngqfreemax", &ngqfreemax);
+SYSCTL_INT(_net_graph, OID_AUTO, ngqfreemax, CTLFLAG_RD, &ngqfreemax,
+    0, "Maximum number of free queue items to cache");
+
 static const int		ngqfreelow = 4; /* try malloc if free < this */
 static volatile int		ngqfreesize;	/* number of cached entries */
 #ifdef	NETGRAPH_DEBUG