[PATCH] netvsc: optimize stats counters performance

[Morten Brørup]

Optimized the performance of updating the statistics counters by reducing
the number of branches.

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

Signed-off-by: Morten Brørup <m...@smartsharesystems.com>
---
 drivers/net/netvsc/hn_rxtx.c | 32 ++++++++++----------------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/drivers/net/netvsc/hn_rxtx.c b/drivers/net/netvsc/hn_rxtx.c
index 9bf1ec5509..b704b2c971 100644
--- a/drivers/net/netvsc/hn_rxtx.c
+++ b/drivers/net/netvsc/hn_rxtx.c
@@ -110,30 +110,18 @@ hn_update_packet_stats(struct hn_stats *stats, const 
struct rte_mbuf *m)
        uint32_t s = m->pkt_len;
        const struct rte_ether_addr *ea;
 
-       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]++;
-       }
+       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]++;
 
        ea = rte_pktmbuf_mtod(m, const struct rte_ether_addr *);
-       if (rte_is_multicast_ether_addr(ea)) {
-               if (rte_is_broadcast_ether_addr(ea))
-                       stats->broadcast++;
-               else
-                       stats->multicast++;
-       }
+       RTE_BUILD_BUG_ON(offsetof(struct hn_stats, broadcast) !=
+                       offsetof(struct hn_stats, multicast) + 
sizeof(uint64_t));
+       if (unlikely(rte_is_multicast_ether_addr(ea)))
+               (&stats->multicast)[rte_is_broadcast_ether_addr(ea)]++;
 }
 
 static inline unsigned int hn_rndis_pktlen(const struct rndis_packet_msg *pkt)
-- 
2.43.0