[ovs-dev] [PATCH] dpdk: Ditch MAX_PKT_BURST macro.

[Ethan Jackson]

The MAX_PKT_BURST and NETDEV_MAX_RX_BATCH macros had a confusing
relationship.  They basically purport to do the same thing, making it
unclear which is the source of truth.

Furthermore, while NETDEV_MAX_RX_BATCH was 256, MAX_PKT_BURST was 32,
meaning we never process a batch larger than 32 packets further adding
to the confusion.

This patch resolves the issue by removing MAX_PKT_BURST completely,
and shrinking the new NETDEV_MAX_BURST macro to only 32.  This should
have no change in the execution path except shrinking a couple of
structs and memory allocations (can't hurt).

Signed-off-by: Ethan Jackson <ethan at nicira.com>
---
 lib/dpif-netdev.c | 10 +++++-----
 lib/netdev-dpdk.c |  7 ++-----
 lib/netdev.h      |  2 +-
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index f1d65f5..4216865 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -2500,7 +2500,7 @@ dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread *pmd,
                            struct dp_netdev_port *port,
                            struct netdev_rxq *rxq)
 {
-    struct dp_packet *packets[NETDEV_MAX_RX_BATCH];
+    struct dp_packet *packets[NETDEV_MAX_BURST];
     int error, cnt;
 
     cycles_count_start(pmd);
@@ -3027,7 +3027,7 @@ struct packet_batch {
 
     struct dp_netdev_flow *flow;
 
-    struct dp_packet *packets[NETDEV_MAX_RX_BATCH];
+    struct dp_packet *packets[NETDEV_MAX_BURST];
 };
 
 static inline void
@@ -3397,7 +3397,7 @@ dp_execute_cb(void *aux_, struct dp_packet **packets, int cnt,
 
     case OVS_ACTION_ATTR_TUNNEL_PUSH:
         if (*depth < MAX_RECIRC_DEPTH) {
-            struct dp_packet *tnl_pkt[NETDEV_MAX_RX_BATCH];
+            struct dp_packet *tnl_pkt[NETDEV_MAX_BURST];
             int err;
 
             if (!may_steal) {
@@ -3423,7 +3423,7 @@ dp_execute_cb(void *aux_, struct dp_packet **packets, int cnt,
 
             p = dp_netdev_lookup_port(dp, portno);
             if (p) {
-                struct dp_packet *tnl_pkt[NETDEV_MAX_RX_BATCH];
+                struct dp_packet *tnl_pkt[NETDEV_MAX_BURST];
                 int err;
 
                 if (!may_steal) {
@@ -3485,7 +3485,7 @@ dp_execute_cb(void *aux_, struct dp_packet **packets, int cnt,
 
     case OVS_ACTION_ATTR_RECIRC:
         if (*depth < MAX_RECIRC_DEPTH) {
-            struct dp_packet *recirc_pkts[NETDEV_MAX_RX_BATCH];
+            struct dp_packet *recirc_pkts[NETDEV_MAX_BURST];
 
             if (!may_steal) {
                dp_netdev_clone_pkt_batch(recirc_pkts, packets, cnt);
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index 505ab75..b06f92a 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -99,8 +99,6 @@ BUILD_ASSERT_DECL((MAX_NB_MBUF / ROUND_DOWN_POW2(MAX_NB_MBUF/MIN_NB_MBUF))
 #define TX_HTHRESH 0  /* Default values of TX host threshold reg. */
 #define TX_WTHRESH 0  /* Default values of TX write-back threshold reg. */
 
-#define MAX_PKT_BURST 32           /* Max burst size for RX/TX */
-
 /* Character device cuse_dev_name. */
 char *cuse_dev_name = NULL;
 
@@ -862,7 +860,7 @@ netdev_dpdk_vhost_rxq_recv(struct netdev_rxq *rxq_,
     nb_rx = rte_vhost_dequeue_burst(virtio_dev, qid,
                                     vhost_dev->dpdk_mp->mp,
                                     (struct rte_mbuf **)packets,
-                                    MAX_PKT_BURST);
+                                    NETDEV_MAX_BURST);
     if (!nb_rx) {
         return EAGAIN;
     }
@@ -889,8 +887,7 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet **packets,
 
     nb_rx = rte_eth_rx_burst(rx->port_id, rxq_->queue_id,
                              (struct rte_mbuf **) packets,
-                             MIN((int) NETDEV_MAX_RX_BATCH,
-                                 (int) MAX_PKT_BURST));
+                             NETDEV_MAX_BURST);
     if (!nb_rx) {
         return EAGAIN;
     }
diff --git a/lib/netdev.h b/lib/netdev.h
index 71c0af1..9d412ee 100644
--- a/lib/netdev.h
+++ b/lib/netdev.h
@@ -338,7 +338,7 @@ typedef void netdev_dump_queue_stats_cb(unsigned int queue_id,
 int netdev_dump_queue_stats(const struct netdev *,
                             netdev_dump_queue_stats_cb *, void *aux);
 
-enum { NETDEV_MAX_RX_BATCH = 256 };     /* Maximum number packets in rx_recv() batch. */
+enum { NETDEV_MAX_BURST = 32 }; /* Maximum number packets in a batch. */
 extern struct seq *tnl_conf_seq;
 
 #ifdef  __cplusplus
-- 
1.9.1