vke(4) - Add a tunable to set the max number of mbuf clusters per device.

* Also cap it to 256 mbuf clusters by default.

diff --git a/share/man/man7/vkernel.7 b/share/man/man7/vkernel.7
index ea2666b..da3d703 100644 (file)
--- a/share/man/man7/vkernel.7
+++ b/share/man/man7/vkernel.7
@@ -29,7 +29,7 @@
 .\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd February 22, 2013
+.Dd March 6, 2013
 .Dt VKERNEL 7
 .Os
 .Sh NAME
@@ -290,6 +290,11 @@ variable
 holds the unit number of the associated
 .Xr tap 4
 device.
+.Pp
+By default, half of the total mbuf clusters available is distributed equally
+among all the vke devices up to 256. This can be overriden with the tunable
+.Va hw.vke.max_ringsize .
+Take into account the number passed will be aligned to the lower power of two.
 .Sh SIGNALS
 The virtual kernel only enables
 .Dv SIGQUIT

diff --git a/sys/dev/virtual/vkernel/net/if_vke.c b/sys/dev/virtual/vkernel/net/if_vke.c
index f74d5fe..a98bf33 100644 (file)
--- a/sys/dev/virtual/vkernel/net/if_vke.c
+++ b/sys/dev/virtual/vkernel/net/if_vke.c
@@ -79,6 +79,13 @@ struct vke_fifo {
 };
 typedef struct vke_fifo *fifo_t;
 
+/* Default value for a long time */
+#define VKE_DEFAULT_RINGSIZE   256
+static int vke_max_ringsize = 0;
+TUNABLE_INT("hw.vke.max_ringsize", &vke_max_ringsize);
+
+#define LOW_POW_2(n)   (1 << (fls(n) - 1))
+
 struct vke_softc {
        struct arpcom           arpcom;
        int                     sc_fd;
@@ -768,18 +775,16 @@ havemac:
        sc->sc_addr = info->netif_addr;
        sc->sc_mask = info->netif_mask;
 
-       /*
-        * Calculate the number of mbuf clusters we are going to use
-        * up to 50% of the total mbuf clusters available in the
-        * system.
-        * In the case our vkernel has so little mem that it can't
-        * allocate even VKE_CHUNK for every vke(4) device, just panic.
-        */
-       nmbufs = nmbclusters / (NetifNum * 2);
-       sc->sc_ringsize = (1 << (fls(nmbufs) - 1));
-
-       KASSERT(sc->sc_ringsize >= VKE_CHUNK,
-           ("Not enough mbuf clusters for %d vke devices", NetifNum));
+       if (vke_max_ringsize == 0) {
+               nmbufs = nmbclusters / (NetifNum * 2);
+               sc->sc_ringsize = LOW_POW_2(nmbufs);
+               if (sc->sc_ringsize > VKE_DEFAULT_RINGSIZE)
+                       sc->sc_ringsize = VKE_DEFAULT_RINGSIZE;
+       } else if (vke_max_ringsize >= VKE_CHUNK) {     /* Tunable specified */
+               sc->sc_ringsize = LOW_POW_2(vke_max_ringsize);
+       } else {
+               sc->sc_ringsize = LOW_POW_2(VKE_CHUNK);
+       }
 
        ifp = &sc->arpcom.ac_if;
        if_initname(ifp, VKE_DEVNAME, sc->sc_unit);