Reduce the amount of sent TX producer notifications; from FreeBSD

diff --git a/sys/dev/pv/if_xnf.c b/sys/dev/pv/if_xnf.c
index 1d8f2c4..3580417 100644 (file)
--- a/sys/dev/pv/if_xnf.c
+++ b/sys/dev/pv/if_xnf.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if_xnf.c,v 1.24 2016/07/28 17:35:13 mikeb Exp $       */
+/*     $OpenBSD: if_xnf.c,v 1.25 2016/07/29 18:31:22 mikeb Exp $       */
 
 /*
  * Copyright (c) 2015, 2016 Mike Belopuhov
@@ -468,7 +468,7 @@ xnf_start(struct ifnet *ifp)
        struct xnf_tx_ring *txr = sc->sc_tx_ring;
        struct mbuf *m;
        int pkts = 0;
-       uint32_t prod;
+       uint32_t prod, oprod;
 
        if (!(ifp->if_flags & IFF_RUNNING) || ifq_is_oactive(&ifp->if_snd))
                return;
@@ -476,7 +476,7 @@ xnf_start(struct ifnet *ifp)
        bus_dmamap_sync(sc->sc_dmat, sc->sc_tx_rmap, 0, 0,
            BUS_DMASYNC_POSTREAD);
 
-       prod = txr->txr_prod;
+       prod = oprod = txr->txr_prod;
 
        for (;;) {
                if ((XNF_TX_DESC - (prod - sc->sc_tx_cons)) <
@@ -505,7 +505,10 @@ xnf_start(struct ifnet *ifp)
        }
        if (pkts > 0) {
                txr->txr_prod = prod;
-               xen_intr_signal(sc->sc_xih);
+               bus_dmamap_sync(sc->sc_dmat, sc->sc_tx_rmap, 0, 0,
+                   BUS_DMASYNC_PREREAD | BUS_DMASYNC_PREWRITE);
+               if (prod - txr->txr_prod_event < prod - oprod)
+                       xen_intr_signal(sc->sc_xih);
                ifp->if_timer = 5;
        }
 }