[RFC PATCH net-next] net: pktgen: packet bursting via skb->xmit_more

* [RFC PATCH net-next] net: pktgen: packet bursting via skb->xmit_more
@ 2014-09-26  0:46 Alexei Starovoitov
  2014-09-26  1:20 ` Eric Dumazet
                   ` (2 more replies)
  0 siblings, 3 replies; 29+ messages in thread
From: Alexei Starovoitov @ 2014-09-26  0:46 UTC (permalink / raw)
  To: David S. Miller
  Cc: Jesper Dangaard Brouer, Eric Dumazet, John Fastabend, netdev

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

burst=1 is a 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:13.6 Mpps
burst=3  tx:14.5 Mpps full 10G line rate

usec 1 (default):
burst=1,4,100 tx:3.9 Mpps

usec 0:
burst=1  tx:4.9 Mpps
burst=2  tx:6.6 Mpps
burst=3  tx:7.9 Mpps
burst=4  tx:8.7 Mpps
burst=8  tx:10.3 Mpps
burst=128  tx:12.4 Mpps

Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
---

tx queue size, irq affinity left in default.
pause frames are off.

Nice to finally see line rate generated by one cpu

Comparing to Jesper patch this one amortizes the cost
of spin_lock and atomic_inc by doing HARD_TX_LOCK and
atomic_add(N) once across N packets.

 net/core/pktgen.c |   33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 5c728aa..47557ba 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 */
+	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)
@@ -3299,7 +3313,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 {
 	struct net_device *odev = pkt_dev->odev;
 	struct netdev_queue *txq;
-	int ret;
+	int burst_cnt, ret;
+	bool more;
 
 	/* If device is offline, then don't send */
 	if (unlikely(!netif_running(odev) || !netif_carrier_ok(odev))) {
@@ -3347,8 +3362,14 @@ 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(pkt_dev->burst, &pkt_dev->skb->users);
+
+	burst_cnt = 0;
+
+xmit_more:
+	more = ++burst_cnt < pkt_dev->burst;
+
+	ret = netdev_start_xmit(pkt_dev->skb, odev, txq, more);
 
 	switch (ret) {
 	case NETDEV_TX_OK:
@@ -3356,6 +3377,8 @@ 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 (more)
+			goto xmit_more;
 		break;
 	case NET_XMIT_DROP:
 	case NET_XMIT_CN:
@@ -3374,6 +3397,9 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 		atomic_dec(&(pkt_dev->skb->users));
 		pkt_dev->last_ok = 0;
 	}
+
+	if (unlikely(pkt_dev->burst - burst_cnt > 0))
+		atomic_sub(pkt_dev->burst - burst_cnt, &pkt_dev->skb->users);
 unlock:
 	HARD_TX_UNLOCK(odev, txq);
 
@@ -3572,6 +3598,7 @@ 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);
-- 
1.7.9.5

^ permalink raw reply related	[flat|nested] 29+ messages in thread