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Date: Tue, 30 Sep 2014 17:03:40 -0700
From: Alexei Starovoitov <ast@...mgrid.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
netdev@...r.kernel.org
Subject: [PATCH net-next] 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@...mgrid.com>
---
RFC -> v1:
- added netif_xmit_frozen_or_drv_stopped() check, since bnx2x
stops the queue and returns TX_OK (suggested by Eric)
- read pkt_dev->burst once to avoid races (suggested by Eric)
- changed 'int burst' to 'unsigned int burst'
- updated doc
- tested on ixgbe, mlx4, bnx2x
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.
I didn't add Jesper and Eric's acks. Guys, please re-ack
if you still think it's ok. Thanks!
Documentation/networking/pktgen.txt | 3 +++
net/core/pktgen.c | 32 ++++++++++++++++++++++++++++++--
2 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/Documentation/networking/pktgen.txt b/Documentation/networking/pktgen.txt
index 0dffc6e37902..6915c6b27869 100644
--- a/Documentation/networking/pktgen.txt
+++ b/Documentation/networking/pktgen.txt
@@ -99,6 +99,9 @@ Examples:
pgset "clone_skb 1" sets the number of copies of the same packet
pgset "clone_skb 0" use single SKB for all transmits
+ pgset "burst 8" uses xmit_more API to queue 8 copies of the same
+ packet and update HW tx queue tail pointer once.
+ "burst 1" is the default
pgset "pkt_size 9014" sets packet size to 9014
pgset "frags 5" packet will consist of 5 fragments
pgset "count 200000" sets number of packets to send, set to zero
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 5c728aaf8d6c..fe53aa57bc5c 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)
@@ -3297,8 +3311,10 @@ 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), burst_cnt;
struct net_device *odev = pkt_dev->odev;
struct netdev_queue *txq;
+ bool more;
int ret;
/* If device is offline, then don't send */
@@ -3347,8 +3363,14 @@ 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(burst, &pkt_dev->skb->users);
+
+ burst_cnt = 0;
+
+xmit_more:
+ more = ++burst_cnt < burst;
+
+ ret = netdev_start_xmit(pkt_dev->skb, odev, txq, more);
switch (ret) {
case NETDEV_TX_OK:
@@ -3356,6 +3378,8 @@ 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 && !netif_xmit_frozen_or_drv_stopped(txq))
+ goto xmit_more;
break;
case NET_XMIT_DROP:
case NET_XMIT_CN:
@@ -3374,6 +3398,9 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
atomic_dec(&(pkt_dev->skb->users));
pkt_dev->last_ok = 0;
}
+
+ if (unlikely(burst - burst_cnt > 0))
+ atomic_sub(burst - burst_cnt, &pkt_dev->skb->users);
unlock:
HARD_TX_UNLOCK(odev, txq);
@@ -3572,6 +3599,7 @@ 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
--
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