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, 10 insertions, 5 deletions

diff --git a/sys/arm/xscale/ixp425/if_npe.c b/sys/arm/xscale/ixp425/if_npe.c
index f50a868..3d174e7 100644
--- a/sys/arm/xscale/ixp425/if_npe.c
+++ b/sys/arm/xscale/ixp425/if_npe.c
@@ -229,7 +229,7 @@ static void	npe_getmac(struct npe_softc *sc, u_char *eaddr);
 static void	npe_txdone(int qid, void *arg);
 static int	npe_rxbuf_init(struct npe_softc *, struct npebuf *,
 			struct mbuf *);
-static void	npe_rxdone(int qid, void *arg);
+static int	npe_rxdone(int qid, void *arg);
 static void	npeinit(void *);
 static void	npestart_locked(struct ifnet *);
 static void	npestart(struct ifnet *);
@@ -777,7 +777,7 @@ npe_activate(device_t dev)
 	 */
 	sc->rx_qid = npeconfig[sc->sc_npeid].rx_qid;
 	ixpqmgr_qconfig(sc->rx_qid, npe_rxbuf, 0,  1,
-		IX_QMGR_Q_SOURCE_ID_NOT_E, npe_rxdone, sc);
+		IX_QMGR_Q_SOURCE_ID_NOT_E, (qconfig_hand_t *)npe_rxdone, sc);
 	sc->rx_freeqid = npeconfig[sc->sc_npeid].rx_freeqid;
 	ixpqmgr_qconfig(sc->rx_freeqid,	npe_rxbuf, 0, npe_rxbuf/2, 0, NULL, sc);
 	/*
@@ -1091,7 +1091,7 @@ npe_rxbuf_init(struct npe_softc *sc, struct npebuf *npe, struct mbuf *m)
  * from the hardware queue and pass the frames up the
  * stack. Pass the rx buffers to the free list.
  */
-static void
+static int
 npe_rxdone(int qid, void *arg)
 {
 #define	P2V(a, dma) \
@@ -1099,6 +1099,7 @@ npe_rxdone(int qid, void *arg)
 	struct npe_softc *sc = arg;
 	struct npedma *dma = &sc->rxdma;
 	uint32_t entry;
+	int rx_npkts = 0;
 
 	while (ixpqmgr_qread(qid, &entry) == 0) {
 		struct npebuf *npe = P2V(NPE_QM_Q_ADDR(entry), dma);
@@ -1132,6 +1133,7 @@ npe_rxdone(int qid, void *arg)
 
 			ifp->if_ipackets++;
 			ifp->if_input(ifp, mrx);
+			rx_npkts++;
 		} else {
 			/* discard frame and re-use mbuf */
 			m = npe->ix_m;
@@ -1143,19 +1145,22 @@ npe_rxdone(int qid, void *arg)
 			/* XXX should not happen */
 		}
 	}
+	return (rx_npkts);
 #undef P2V
 }
 
 #ifdef DEVICE_POLLING
-static void
+static int
 npe_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 {
 	struct npe_softc *sc = ifp->if_softc;
+	int rx_npkts = 0;
 
 	if (ifp->if_drv_flags & IFF_DRV_RUNNING) {
-		npe_rxdone(sc->rx_qid, sc);
+		rx_npkts = npe_rxdone(sc->rx_qid, sc);
 		npe_txdone(sc->tx_doneqid, sc);	/* XXX polls both NPE's */
 	}
+	return (rx_npkts);
 }
 #endif /* DEVICE_POLLING */