- Avoid lock contention in the if_transmit callback by using trylock and

 enqueueing the frames when it fails. This way there is some latency
 removed from the transmitting path.
- If IFF_DRV_OACTIVE is set (and also if IFF_DRV_RUNNING is not) just
 enqueue the desired frames and return successful transmit. This way we
 avoid to return errors on transmit side and resulting in
 possible out-of-order frames. Please note that IFF_DRV_OACTIVE is set
 everytime we get the threshold ring hit, so this can be happening quite
 often.

Submitted by:	Attilio.Rao@isilon.com
MFC after:5 days

diff --git a/sys/dev/bxe/bxe.c b/sys/dev/bxe/bxe.c
index f3e59640fb84efe8340a7cb1087f66ca83cfd59e..274cc5b4ca3e23b72d62027d8e90a82ffd0820b2 100644 (file)
--- a/sys/dev/bxe/bxe.c
+++ b/sys/dev/bxe/bxe.c
@@ -5999,19 +5999,26 @@ bxe_tx_mq_start_locked(struct bxe_softc    *sc,
 
     rc = tx_count = 0;
 
+    BXE_FP_TX_LOCK_ASSERT(fp);
+
     if (!tx_br) {
         BLOGE(sc, "Multiqueue TX and no buf_ring!\n");
         return (EINVAL);
     }
 
+    if (!sc->link_vars.link_up ||
+        (ifp->if_drv_flags &
+        (IFF_DRV_RUNNING | IFF_DRV_OACTIVE)) != IFF_DRV_RUNNING) {
+        rc = drbr_enqueue_drv(ifp, tx_br, m);
+        goto bxe_tx_mq_start_locked_exit;
+    }
+
     /* fetch the depth of the driver queue */
     depth = drbr_inuse_drv(ifp, tx_br);
     if (depth > fp->eth_q_stats.tx_max_drbr_queue_depth) {
         fp->eth_q_stats.tx_max_drbr_queue_depth = depth;
     }
 
-    BXE_FP_TX_LOCK_ASSERT(fp);
-
     if (m == NULL) {
         /* no new work, check for pending frames */
         next = drbr_dequeue_drv(ifp, tx_br);
@@ -6103,26 +6110,11 @@ bxe_tx_mq_start(struct ifnet *ifp,
 
     fp = &sc->fp[fp_index];
 
-    if (!(if_getdrvflags(ifp) & IFF_DRV_RUNNING)) {
-        BLOGW(sc, "Interface not running, ignoring transmit request\n");
-        return (ENETDOWN);
-    }
-
-    if (if_getdrvflags(ifp) & IFF_DRV_OACTIVE) {
-        BLOGW(sc, "Interface TX queue is full, ignoring transmit request\n");
-        return (EBUSY);
-    }
-
-    if (!sc->link_vars.link_up) {
-        BLOGW(sc, "Interface link is down, ignoring transmit request\n");
-        return (ENETDOWN);
-    }
-
-    /* XXX change to TRYLOCK here and if failed then schedule taskqueue */
-
-    BXE_FP_TX_LOCK(fp);
-    rc = bxe_tx_mq_start_locked(sc, ifp, fp, m);
-    BXE_FP_TX_UNLOCK(fp);
+    if (BXE_FP_TX_TRYLOCK(fp)) {
+        rc = bxe_tx_mq_start_locked(sc, ifp, fp, m);
+        BXE_FP_TX_UNLOCK(fp);
+    } else
+        rc = drbr_enqueue_drv(ifp, fp->tx_br, m);
 
     return (rc);
 }

diff --git a/sys/dev/bxe/bxe.h b/sys/dev/bxe/bxe.h
index 5fb31a32ba87904c4c63593a74f0f50cb9f236b1..980a91fc759ce9eb2b78988e77c2399803a3efe9 100644 (file)
--- a/sys/dev/bxe/bxe.h
+++ b/sys/dev/bxe/bxe.h
@@ -582,6 +582,7 @@ struct bxe_fastpath {
 #define BXE_FP_TX_LOCK(fp)        mtx_lock(&fp->tx_mtx)
 #define BXE_FP_TX_UNLOCK(fp)      mtx_unlock(&fp->tx_mtx)
 #define BXE_FP_TX_LOCK_ASSERT(fp) mtx_assert(&fp->tx_mtx, MA_OWNED)
+#define BXE_FP_TX_TRYLOCK(fp)     mtx_trylock(&fp->tx_mtx)
 
 #define BXE_FP_RX_LOCK(fp)        mtx_lock(&fp->rx_mtx)
 #define BXE_FP_RX_UNLOCK(fp)      mtx_unlock(&fp->rx_mtx)