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Much to my surprise, IFQ_DRV_DEQUEUE() can return a null mbuf even if

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!IFQ_DRV_IS_EMPTY().  Taking this into account,  I re-structured the
transmit routine so as to avoid adding another if/then in the
critical path.

Thanks to brueffer for showing my how to test with altq/pf.
This commit is contained in:
Andrew Gallatin 2006-06-14 19:32:00 +00:00
parent dea060ff55
commit 6d914a32ff
1 changed files with 11 additions and 13 deletions
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24
sys/dev/mxge/if_mxge.c
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@ -1277,32 +1277,30 @@ mxge_encap(mxge_softc_t *sc, struct mbuf *m)
}
static void
static inline void
mxge_start_locked(mxge_softc_t *sc)
{
int avail;
struct mbuf *m;
struct ifnet *ifp;
ifp = sc->ifp;
while (!IFQ_DRV_IS_EMPTY(&ifp->if_snd)) {
/* dequeue the packet */
while ((sc->tx.mask - (sc->tx.req - sc->tx.done))
> MXGE_MAX_SEND_DESC) {
IFQ_DRV_DEQUEUE(&ifp->if_snd, m);
if (m == NULL) {
return;
}
/* let BPF see it */
BPF_MTAP(ifp, m);
/* give it to the nic */
mxge_encap(sc, m);
/* leave an extra slot keep the ring from wrapping */
avail = sc->tx.mask - (sc->tx.req - sc->tx.done);
if (avail < MXGE_MAX_SEND_DESC) {
sc->ifp->if_drv_flags |= IFF_DRV_OACTIVE;
return;
}
}
/* ran out of transmit slots */
sc->ifp->if_drv_flags |= IFF_DRV_OACTIVE;
}
static void