[PATCH v4] virtio: optimize stats counters performance

["Morten Brørup" <mb@smartsharesystems.com>]

Optimized the performance of updating the virtio statistics counters by
reducing the number of branches and inlining the function.

Ordered the packet size comparisons according to the probability with
typical internet traffic mix.

Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
---
v4:
* Consider multicast/broadcast packets unlikely.
v3:
* Eliminated a local variable.
* Note: Substituted sizeof(uint32_t)*4 by 32UL, using unsigned long type
  to keep optimal offsetting in generated assembler output.
* Removed unnecessary curly braces.
v2:
* Fixed checkpatch warning about line length.
---
 drivers/net/virtio/virtio_rxtx.c | 34 --------------------------------
 drivers/net/virtio/virtio_rxtx.h | 23 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 36 deletions(-)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index f69b9453a2..bb04fd7d43 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -81,40 +81,6 @@ vq_ring_free_chain(struct virtqueue *vq, uint16_t desc_idx)
 	dp->next = VQ_RING_DESC_CHAIN_END;
 }
 
-void
-virtio_update_packet_stats(struct virtnet_stats *stats, struct rte_mbuf *mbuf)
-{
-	uint32_t s = mbuf->pkt_len;
-	struct rte_ether_addr *ea;
-
-	stats->bytes += s;
-
-	if (s == 64) {
-		stats->size_bins[1]++;
-	} else if (s > 64 && s < 1024) {
-		uint32_t bin;
-
-		/* count zeros, and offset into correct bin */
-		bin = (sizeof(s) * 8) - rte_clz32(s) - 5;
-		stats->size_bins[bin]++;
-	} else {
-		if (s < 64)
-			stats->size_bins[0]++;
-		else if (s < 1519)
-			stats->size_bins[6]++;
-		else
-			stats->size_bins[7]++;
-	}
-
-	ea = rte_pktmbuf_mtod(mbuf, struct rte_ether_addr *);
-	if (rte_is_multicast_ether_addr(ea)) {
-		if (rte_is_broadcast_ether_addr(ea))
-			stats->broadcast++;
-		else
-			stats->multicast++;
-	}
-}
-
 static inline void
 virtio_rx_stats_updated(struct virtnet_rx *rxvq, struct rte_mbuf *m)
 {
diff --git a/drivers/net/virtio/virtio_rxtx.h b/drivers/net/virtio/virtio_rxtx.h
index afc4b74534..0f938ab145 100644
--- a/drivers/net/virtio/virtio_rxtx.h
+++ b/drivers/net/virtio/virtio_rxtx.h
@@ -35,7 +35,26 @@ struct virtnet_tx {
 };
 
 int virtio_rxq_vec_setup(struct virtnet_rx *rxvq);
-void virtio_update_packet_stats(struct virtnet_stats *stats,
-				struct rte_mbuf *mbuf);
+
+static inline void
+virtio_update_packet_stats(struct virtnet_stats *const stats, const struct rte_mbuf *const mbuf)
+{
+	uint32_t s = mbuf->pkt_len;
+	const struct rte_ether_addr *ea = rte_pktmbuf_mtod(mbuf, const struct rte_ether_addr *);
+
+	stats->bytes += s;
+
+	if (s >= 1024)
+		stats->size_bins[6 + (s > 1518)]++;
+	else if (s <= 64)
+		stats->size_bins[s >> 6]++;
+	else
+		stats->size_bins[32UL - rte_clz32(s) - 5]++;
+
+	RTE_BUILD_BUG_ON(offsetof(struct virtnet_stats, broadcast) !=
+			offsetof(struct virtnet_stats, multicast) + sizeof(uint64_t));
+	if (unlikely(rte_is_multicast_ether_addr(ea)))
+		(&stats->multicast)[rte_is_broadcast_ether_addr(ea)]++;
+}
 
 #endif /* _VIRTIO_RXTX_H_ */
-- 
2.43.0