svn commit: r285973 - head/sys/dev/bxe

[David C Somayajulu]

Author: davidcs
Date: Tue Jul 28 19:15:44 2015
New Revision: 285973
URL: https://svnweb.freebsd.org/changeset/base/285973

Log:
  - 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 at isilon.com
  MFC after:5 days

Modified:
  head/sys/dev/bxe/bxe.c
  head/sys/dev/bxe/bxe.h

Modified: head/sys/dev/bxe/bxe.c
==============================================================================
--- head/sys/dev/bxe/bxe.c	Tue Jul 28 18:41:28 2015	(r285972)
+++ head/sys/dev/bxe/bxe.c	Tue Jul 28 19:15:44 2015	(r285973)
@@ -5999,19 +5999,26 @@ bxe_tx_mq_start_locked(struct bxe_softc 
 
     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);
 }

Modified: head/sys/dev/bxe/bxe.h
==============================================================================
--- head/sys/dev/bxe/bxe.h	Tue Jul 28 18:41:28 2015	(r285972)
+++ head/sys/dev/bxe/bxe.h	Tue Jul 28 19:15:44 2015	(r285973)
@@ -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)