The drbr(9) API appeared to be so unclear, that most drivers in

tree used it incorrectly, which lead to inaccurate overrated
if_obytes accounting. The drbr(9) used to update ifnet stats on
drbr_enqueue(), which is not accurate since enqueuing doesn't
imply successful processing by driver. Dequeuing neither mean
that. Most drivers also called drbr_stats_update() which did
accounting again, leading to doubled if_obytes statistics. And
in case of severe transmitting, when a packet could be several
times enqueued and dequeued it could have been accounted several
times.

o Thus, make drbr(9) API thinner. Now drbr(9) merely chooses between
  ALTQ queueing or buf_ring(9) queueing.
  - It doesn't touch the buf_ring stats any more.
  - It doesn't touch ifnet stats anymore.
  - drbr_stats_update() no longer exists.

o buf_ring(9) handles its stats itself:
  - It handles br_drops itself.
  - br_prod_bytes stats are dropped. Rationale: no one ever
    reads them but update of a common counter on every packet
    negatively affects performance due to excessive cache
    invalidation.
  - buf_ring_enqueue_bytes() reduced to buf_ring_enqueue(), since
    we no longer account bytes.

o Drivers handle their stats theirselves: if_obytes, if_omcasts.

o mlx4(4), igb(4), em(4), vxge(4), oce(4) and  ixv(4) no longer
  use drbr_stats_update(), and update ifnet stats theirselves.

o bxe(4) was the most correct driver, it didn't call
  drbr_stats_update(), thus it was the only driver accurate under
  moderate load. Now it also maintains stats itself.

o ixgbe(4) had already taken stats from hardware, so just
  - drop software stats updating.
  - take multicast packet count from hardware as well.

o mxge(4) just no longer needs NO_SLOW_STATS define.

o cxgb(4), cxgbe(4) need no change, since they obtain stats
  from hardware.

Reviewed by:	jfv, gnn

share/man/man9/buf_ring.9

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 30, 2012
+.Dd September 27, 2012
 .Dt BUF_RING 9
 .Os
 .Sh NAME
@@ -33,7 +33,6 @@
 .Nm buf_ring_alloc ,
 .Nm buf_ring_free ,
 .Nm buf_ring_enqueue ,
-.Nm buf_ring_enqueue_bytes ,
 .Nm buf_ring_dequeue_mc ,
 .Nm buf_ring_dequeue_sc ,
 .Nm buf_ring_count ,
@@ -50,8 +49,6 @@
 .Fn buf_ring_free "struct buf_ring *br" "struct malloc_type *type"
 .Ft int
 .Fn buf_ring_enqueue "struct buf_ring *br" "void *buf"
-.Ft int
-.Fn buf_ring_enqueue_bytes "struct buf_ring *br" "void *buf" "int bytes"
 .Ft void *
 .Fn buf_ring_dequeue_mc "struct buf_ring *br"
 .Ft void *
@@ -91,12 +88,6 @@ The
 function is used to enqueue a buffer to a buf_ring.
 .Pp
 The
-.Fn buf_ring_enqueue_bytes
-function is used to enqueue a buffer to a buf_ring and increment the
-number of bytes enqueued by
-.Fa bytes .
-.Pp
-The
 .Fn buf_ring_dequeue_mc
 function is a multi-consumer safe way of dequeueing elements from a buf_ring.
 .Pp
@@ -134,9 +125,7 @@ otherwise.
 .Sh RETURN VALUES
 The
 .Fn buf_ring_enqueue
-and
+function return
-.Fn buf_ring_enqueue_bytes
-functions return
 .Er ENOBUFS
 if there are no available slots in the buf_ring.
 .Sh HISTORY

share/man/man9/drbr.9

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 30, 2012
+.Dd September 27, 2012
 .Dt DRBR 9
 .Os
 .Sh NAME
@@ -37,7 +37,6 @@
 .Nm drbr_flush ,
 .Nm drbr_empty ,
 .Nm drbr_inuse ,
-.Nm drbr_stats_update ,
 .Nd network driver interface to buf_ring
 .Sh SYNOPSIS
 .In sys/param.h
@@ -57,8 +56,6 @@
 .Fn drbr_empty "struct ifnet *ifp" "struct buf_ring *br"
 .Ft int
 .Fn drbr_inuse "struct ifnet *ifp" "struct buf_ring *br"
-.Ft void
-.Fn drbr_stats_update "struct ifnet *ifp" "int len" "int mflags"
 .Sh DESCRIPTION
 The
 .Nm
@@ -123,9 +120,6 @@ there will not be more mbufs when
 is actually called.
 Provided the tx queue lock is held there will not be less.
 .Pp
-The
-.Fn drbr_stats_update
-function updates the number of bytes and the number of multicast packets sent.
 .Sh RETURN VALUES
 The
 .Fn drbr_enqueue

sys/dev/bxe/if_bxe.c

@@ -9557,6 +9557,11 @@ bxe_tx_mq_start_locked(struct ifnet *ifp,
 		/* The transmit frame was enqueued successfully. */
 		tx_count++;
 
+		/* Update stats */
+		ifp->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			ifp->if_omcasts++;
+
 		/* Send a copy of the frame to any BPF listeners. */
 		BPF_MTAP(ifp, next);
 

sys/dev/e1000/if_em.c

@@ -922,7 +922,9 @@ em_mq_start_locked(struct ifnet *ifp, struct tx_ring *txr, struct mbuf *m)
                         break;
 		}
 		enq++;
-		drbr_stats_update(ifp, next->m_pkthdr.len, next->m_flags);
+		ifp->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			ifp->if_omcasts++;
 		ETHER_BPF_MTAP(ifp, next);
 		if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0)
                         break;

sys/dev/e1000/if_igb.c

@@ -1014,7 +1014,9 @@ igb_mq_start_locked(struct ifnet *ifp, struct tx_ring *txr, struct mbuf *m)
 			break;
 		}
 		enq++;
-		drbr_stats_update(ifp, next->m_pkthdr.len, next->m_flags);
+		ifp->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			ifp->if_omcasts++;
 		ETHER_BPF_MTAP(ifp, next);
 		if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0)
 			break;

sys/dev/ixgbe/ixgbe.c

@@ -853,7 +853,6 @@ ixgbe_mq_start_locked(struct ifnet *ifp, struct tx_ring *txr, struct mbuf *m)
 			break;
 		}
 		enqueued++;
-		drbr_stats_update(ifp, next->m_pkthdr.len, next->m_flags);
 		/* Send a copy of the frame to the BPF listener */
 		ETHER_BPF_MTAP(ifp, next);
 		if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0)
@@ -5335,6 +5334,7 @@ ixgbe_update_stats_counters(struct adapter *adapter)
 	ifp->if_ibytes = adapter->stats.gorc;
 	ifp->if_obytes = adapter->stats.gotc;
 	ifp->if_imcasts = adapter->stats.mprc;
+	ifp->if_omcasts = adapter->stats.mptc;
 	ifp->if_collisions = 0;
 
 	/* Rx Errors */

sys/dev/ixgbe/ixv.c

@@ -641,7 +641,9 @@ ixv_mq_start_locked(struct ifnet *ifp, struct tx_ring *txr, struct mbuf *m)
 			break;
 		}
 		enqueued++;
-		drbr_stats_update(ifp, next->m_pkthdr.len, next->m_flags);
+		ifp->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			ifp->if_omcasts++;
 		/* Send a copy of the frame to the BPF listener */
 		ETHER_BPF_MTAP(ifp, next);
 		if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0)

sys/dev/mxge/if_mxge.c

@@ -47,8 +47,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/sx.h>
 #include <sys/taskqueue.h>
 
-/* count xmits ourselves, rather than via drbr */
-#define NO_SLOW_STATS
 #include <net/if.h>
 #include <net/if_arp.h>
 #include <net/ethernet.h>

sys/dev/oce/oce_if.c

@@ -1183,7 +1183,9 @@ oce_multiq_transmit(struct ifnet *ifp, struct mbuf *m, struct oce_wq *wq)
 			}  
 			break;
 		}
-		drbr_stats_update(ifp, next->m_pkthdr.len, next->m_flags);
+		ifp->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			ifp->if_omcasts++;
 		ETHER_BPF_MTAP(ifp, next);
 		next = drbr_dequeue(ifp, br);
 	}

sys/dev/vxge/vxge.c

@@ -709,7 +709,9 @@ vxge_mq_send_locked(ifnet_t ifp, vxge_vpath_t *vpath, mbuf_t m_head)
 			VXGE_DRV_STATS(vpath, tx_again);
 			break;
 		}
-		drbr_stats_update(ifp, next->m_pkthdr.len, next->m_flags);
+		ifp->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			ifp->if_omcasts++;
 
 		/* Send a copy of the frame to the BPF listener */
 		ETHER_BPF_MTAP(ifp, next);

sys/net/if_var.h

@@ -590,22 +590,10 @@ do {									\
 } while (0)
 
 #ifdef _KERNEL
-static __inline void
-drbr_stats_update(struct ifnet *ifp, int len, int mflags)
-{
-#ifndef NO_SLOW_STATS
-	ifp->if_obytes += len;
-	if (mflags & M_MCAST)
-		ifp->if_omcasts++;
-#endif
-}
-
 static __inline int
 drbr_enqueue(struct ifnet *ifp, struct buf_ring *br, struct mbuf *m)
 {	
 	int error = 0;
-	int len = m->m_pkthdr.len;
-	int mflags = m->m_flags;
 
 #ifdef ALTQ
 	if (ALTQ_IS_ENABLED(&ifp->if_snd)) {
@@ -613,12 +601,10 @@ drbr_enqueue(struct ifnet *ifp, struct buf_ring *br, struct mbuf *m)
 		return (error);
 	}
 #endif
-	if ((error = buf_ring_enqueue_bytes(br, m, len)) == ENOBUFS) {
+	error = buf_ring_enqueue(br, m);
-		br->br_drops++;
+	if (error)
 		m_freem(m);
-	} else
+
-		drbr_stats_update(ifp, len, mflags);
-	
 	return (error);
 }
 

sys/ofed/drivers/net/mlx4/en_tx.c

@@ -948,7 +948,9 @@ mlx4_en_transmit_locked(struct ifnet *dev, int tx_ind, struct mbuf *m)
 			break;
 		}
 		enqueued++;
-		drbr_stats_update(dev, next->m_pkthdr.len, next->m_flags);
+		dev->if_obytes += next->m_pkthdr.len;
+		if (next->m_flags & M_MCAST)
+			dev->if_omcasts++;
 		/* Send a copy of the frame to the BPF listener */
 		ETHER_BPF_MTAP(dev, next);
 		if ((dev->if_drv_flags & IFF_DRV_RUNNING) == 0)

sys/sys/buf_ring.h

@@ -48,7 +48,6 @@ struct buf_ring {
 	int              	br_prod_mask;
 	uint64_t		br_drops;
 	uint64_t		br_prod_bufs;
-	uint64_t		br_prod_bytes;
 	/*
 	 * Pad out to next L2 cache line
 	 */
@@ -74,7 +73,7 @@ struct buf_ring {
  *
  */
 static __inline int
-buf_ring_enqueue_bytes(struct buf_ring *br, void *buf, int nbytes)
+buf_ring_enqueue(struct buf_ring *br, void *buf)
 {
 	uint32_t prod_head, prod_next;
 	uint32_t cons_tail;
@@ -95,6 +94,7 @@ buf_ring_enqueue_bytes(struct buf_ring *br, void *buf, int nbytes)
 		prod_next = (prod_head + 1) & br->br_prod_mask;
 		
 		if (prod_next == cons_tail) {
+			br->br_drops++;
 			critical_exit();
 			return (ENOBUFS);
 		}
@@ -117,19 +117,11 @@ buf_ring_enqueue_bytes(struct buf_ring *br, void *buf, int nbytes)
 	while (br->br_prod_tail != prod_head)
 		cpu_spinwait();
 	br->br_prod_bufs++;
-	br->br_prod_bytes += nbytes;
 	br->br_prod_tail = prod_next;
 	critical_exit();
 	return (0);
 }
 
-static __inline int
-buf_ring_enqueue(struct buf_ring *br, void *buf)
-{
-
-	return (buf_ring_enqueue_bytes(br, buf, 0));
-}
-
 /*
  * multi-consumer safe dequeue 
  *