net: pktgen: packet bursting via skb->xmit_more

This patch demonstrates the effect of delaying update of HW tailptr.
(based on earlier patch by Jesper)

burst=1 is the default. It sends one packet with xmit_more=false
burst=2 sends one packet with xmit_more=true and
        2nd copy of the same packet with xmit_more=false
burst=3 sends two copies of the same packet with xmit_more=true and
        3rd copy with xmit_more=false

Performance with ixgbe (usec 30):
burst=1  tx:9.2 Mpps
burst=2  tx:13.5 Mpps
burst=3  tx:14.5 Mpps full 10G line rate

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 2 deletions

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 5c728aaf8d6c..443256bdcddc 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -387,6 +387,7 @@ struct pktgen_dev {
         u16 queue_map_min;
         u16 queue_map_max;
         __u32 skb_priority;     /* skb priority field */
+        unsigned int burst;     /* number of duplicated packets to burst */
         int node;               /* Memory node */
 
 #ifdef CONFIG_XFRM
@@ -613,6 +614,9 @@ static int pktgen_if_show(struct seq_file *seq, void *v)
         if (pkt_dev->traffic_class)
                 seq_printf(seq, "     traffic_class: 0x%02x\n", pkt_dev->traffic_class);
 
+        if (pkt_dev->burst > 1)
+                seq_printf(seq, "     burst: %d\n", pkt_dev->burst);
+
         if (pkt_dev->node >= 0)
                 seq_printf(seq, "     node: %d\n", pkt_dev->node);
 
@@ -1124,6 +1128,16 @@ static ssize_t pktgen_if_write(struct file *file,
                         pkt_dev->dst_mac_count);
                 return count;
         }
+        if (!strcmp(name, "burst")) {
+                len = num_arg(&user_buffer[i], 10, &value);
+                if (len < 0)
+                        return len;
+
+                i += len;
+                pkt_dev->burst = value < 1 ? 1 : value;
+                sprintf(pg_result, "OK: burst=%d", pkt_dev->burst);
+                return count;
+        }
         if (!strcmp(name, "node")) {
                 len = num_arg(&user_buffer[i], 10, &value);
                 if (len < 0)
@@ -3297,6 +3311,7 @@ static void pktgen_wait_for_skb(struct pktgen_dev *pkt_dev)
 
 static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 {
+        unsigned int burst = ACCESS_ONCE(pkt_dev->burst);
         struct net_device *odev = pkt_dev->odev;
         struct netdev_queue *txq;
         int ret;
@@ -3347,8 +3362,10 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
                 pkt_dev->last_ok = 0;
                 goto unlock;
         }
-        atomic_inc(&(pkt_dev->skb->users));
-        ret = netdev_start_xmit(pkt_dev->skb, odev, txq, false);
+        atomic_add(burst, &pkt_dev->skb->users);
+
+xmit_more:
+        ret = netdev_start_xmit(pkt_dev->skb, odev, txq, --burst > 0);
 
         switch (ret) {
         case NETDEV_TX_OK:
@@ -3356,6 +3373,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
                 pkt_dev->sofar++;
                 pkt_dev->seq_num++;
                 pkt_dev->tx_bytes += pkt_dev->last_pkt_size;
+                if (burst > 0 && !netif_xmit_frozen_or_drv_stopped(txq))
+                        goto xmit_more;
                 break;
         case NET_XMIT_DROP:
         case NET_XMIT_CN:
@@ -3374,6 +3393,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
                 atomic_dec(&(pkt_dev->skb->users));
                 pkt_dev->last_ok = 0;
         }
+        if (unlikely(burst))
+                atomic_sub(burst, &pkt_dev->skb->users);
 unlock:
         HARD_TX_UNLOCK(odev, txq);
 
@@ -3572,6 +3593,7 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname)
         pkt_dev->svlan_p = 0;
         pkt_dev->svlan_cfi = 0;
         pkt_dev->svlan_id = 0xffff;
+        pkt_dev->burst = 1;
         pkt_dev->node = -1;
 
         err = pktgen_setup_dev(t->net, pkt_dev, ifname);