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, 13 insertions, 8 deletions

diff --git a/sys/dev/ste/if_ste.c b/sys/dev/ste/if_ste.c
index 0e06d7b..5411d08 100644
--- a/sys/dev/ste/if_ste.c
+++ b/sys/dev/ste/if_ste.c
@@ -98,7 +98,7 @@ static void ste_init(void *);
 static void ste_init_locked(struct ste_softc *);
 static void ste_intr(void *);
 static void ste_rxeoc(struct ste_softc *);
-static void ste_rxeof(struct ste_softc *);
+static int ste_rxeof(struct ste_softc *);
 static void ste_txeoc(struct ste_softc *);
 static void ste_txeof(struct ste_softc *);
 static void ste_stats_update(void *);
@@ -620,28 +620,31 @@ ste_setmulti(sc)
 #ifdef DEVICE_POLLING
 static poll_handler_t ste_poll, ste_poll_locked;
 
-static void
+static int
 ste_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 {
 	struct ste_softc *sc = ifp->if_softc;
+	int rx_npkts = 0;
 
 	STE_LOCK(sc);
 	if (ifp->if_drv_flags & IFF_DRV_RUNNING)
-		ste_poll_locked(ifp, cmd, count);
+		rx_npkts = ste_poll_locked(ifp, cmd, count);
 	STE_UNLOCK(sc);
+	return (rx_npkts);
 }
 
-static void
+static int
 ste_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 {
 	struct ste_softc *sc = ifp->if_softc;
+	int rx_npkts;
 
 	STE_LOCK_ASSERT(sc);
 
 	sc->rxcycles = count;
 	if (cmd == POLL_AND_CHECK_STATUS)
 		ste_rxeoc(sc);
-	ste_rxeof(sc);
+	rx_npkts = ste_rxeof(sc);
 	ste_txeof(sc);
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
 		ste_start_locked(ifp);
@@ -667,6 +670,7 @@ ste_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 			ste_init_locked(sc);
 		}
 	}
+	return (rx_npkts);
 }
 #endif /* DEVICE_POLLING */
 
@@ -765,14 +769,14 @@ ste_rxeoc(struct ste_softc *sc)
  * A frame has been uploaded: pass the resulting mbuf chain up to
  * the higher level protocols.
  */
-static void
+static int
 ste_rxeof(sc)
 	struct ste_softc		*sc;
 {
         struct mbuf		*m;
         struct ifnet		*ifp;
 	struct ste_chain_onefrag	*cur_rx;
-	int			total_len = 0, count=0;
+	int			total_len = 0, count=0, rx_npkts = 0;
 	u_int32_t		rxstat;
 
 	STE_LOCK_ASSERT(sc);
@@ -847,9 +851,10 @@ ste_rxeof(sc)
 
 		cur_rx->ste_ptr->ste_status = 0;
 		count++;
+		rx_npkts++;
 	}
 
-	return;
+	return (rx_npkts);
 }
 
 static void