When user_frac in the polling subsystem is low it is going to busy the

CPU for too long period than necessary.  Additively, interfaces are kept
polled (in the tick) even if no more packets are available.
In order to avoid such situations a new generic mechanism can be
implemented in proactive way, keeping track of the time spent on any
packet and fragmenting the time for any tick, stopping the processing
as soon as possible.

In order to implement such mechanism, the polling handler needs to
change, returning the number of packets processed.
While the intended logic is not part of this patch, the polling KPI is
broken by this commit, adding an int return value and the new flag
IFCAP_POLLING_NOCOUNT (which will signal that the return value is
meaningless for the installed handler and checking should be skipped).

Bump __FreeBSD_version in order to signal such situation.

Reviewed by:	emaste
Sponsored by:	Sandvine Incorporated

1 files changed, 7 insertions, 5 deletions

diff --git a/sys/dev/vge/if_vge.c b/sys/dev/vge/if_vge.c
index 5a56eb1..b9eaeaa 100644
--- a/sys/dev/vge/if_vge.c
+++ b/sys/dev/vge/if_vge.c
@@ -156,7 +156,7 @@ static int vge_tx_list_init	(struct vge_softc *);
 static __inline void vge_fixup_rx
 				(struct mbuf *);
 #endif
-static void vge_rxeof		(struct vge_softc *);
+static int vge_rxeof		(struct vge_softc *);
 static void vge_txeof		(struct vge_softc *);
 static void vge_intr		(void *);
 static void vge_tick		(void *);
@@ -1295,7 +1295,7 @@ vge_fixup_rx(m)
  * RX handler. We support the reception of jumbo frames that have
  * been fragmented across multiple 2K mbuf cluster buffers.
  */
-static void
+static int
 vge_rxeof(sc)
 	struct vge_softc	*sc;
 {
@@ -1482,7 +1482,7 @@ vge_rxeof(sc)
 	CSR_WRITE_2(sc, VGE_RXDESC_RESIDUECNT, lim);
 
 
-	return;
+	return (lim);
 }
 
 static void
@@ -1582,17 +1582,18 @@ vge_tick(xsc)
 }
 
 #ifdef DEVICE_POLLING
-static void
+static int
 vge_poll (struct ifnet *ifp, enum poll_cmd cmd, int count)
 {
 	struct vge_softc *sc = ifp->if_softc;
+	int rx_npkts = 0;
 
 	VGE_LOCK(sc);
 	if (!(ifp->if_drv_flags & IFF_DRV_RUNNING))
 		goto done;
 
 	sc->rxcycles = count;
-	vge_rxeof(sc);
+	rx_npkts = vge_rxeof(sc);
 	vge_txeof(sc);
 
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
@@ -1623,6 +1624,7 @@ vge_poll (struct ifnet *ifp, enum poll_cmd cmd, int count)
 	}
 done:
 	VGE_UNLOCK(sc);
+	return (rx_npkts);
 }
 #endif /* DEVICE_POLLING */