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Date: Wed, 27 Aug 2014 23:13:00 +0200
From: Jesper Dangaard Brouer <brouer@...hat.com>
To: Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Daniel Borkmann <dborkman@...hat.com>,
Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc: cwang@...pensource.com
Subject: [RFC PATCH] pktgen: skb bursting via skb->xmit_more API
This patch just demonstrates the effect of delaying the HW tailptr,
the skb->xmit_more API should likely have some wrappers.
One issue is the possible need to flush/write the tailptr on
the exit path... marked with FIXME.
Let me demonstrate the performance effect of bulking packet with pktgen.
These results is a **single** CPU pktgen TX via script:
https://github.com/netoptimizer/network-testing/blob/master/pktgen/pktgen02_burst.sh
Cmdline args:
./pktgen02_burst.sh -i eth5 -d 192.168.21.4 -m 00:12:c0:80:1d:54 -b $skb_burst
Special case skb_burst=1 does not burst, but activates the
skb_burst_count++ and writing to skb->xmit_more.
Performance
skb_burst=0 tx:5614370 pps
skb_burst=1 tx:5571279 pps ( -1.38 ns (worse))
skb_burst=2 tx:6942821 pps ( 35.46 ns)
skb_burst=3 tx:7556214 pps ( 11.69 ns)
skb_burst=4 tx:7740632 pps ( 3.15 ns)
skb_burst=5 tx:7972489 pps ( 3.76 ns)
skb_burst=6 tx:8129856 pps ( 2.43 ns)
skb_burst=7 tx:8281671 pps ( 2.25 ns)
skb_burst=8 tx:8383790 pps ( 1.47 ns)
skb_burst=9 tx:8451248 pps ( 0.95 ns)
skb_burst=10 tx:8503571 pps ( 0.73 ns)
skb_burst=16 tx:8745878 pps ( 3.26 ns)
skb_burst=24 tx:8871629 pps ( 1.62 ns)
skb_burst=32 tx:8945166 pps ( 0.93 ns)
skb_burst=(0 vs 32) improvement:
(1/5614370*10^9)-(1/8945166*10^9) = 66.32 ns
+ 3330796 pps
---
net/core/pktgen.c | 34 +++++++++++++++++++++++++++++++++-
1 files changed, 33 insertions(+), 1 deletions(-)
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 83e2b4b..ac5f7c4 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -269,6 +269,8 @@ struct pktgen_dev {
__u64 allocated_skbs;
__u32 clone_count;
+
+ int skb_burst_count; /* counter for skb_burst */
int last_ok; /* Was last skb sent?
* Or a failed transmit of some sort?
* This will keep sequence numbers in order
@@ -386,6 +388,9 @@ struct pktgen_dev {
u16 queue_map_min;
u16 queue_map_max;
__u32 skb_priority; /* skb priority field */
+ int skb_burst; /* Bursting SKBs by delaying HW
+ * tailptr via skb->xmit_more
+ */
int node; /* Memory node */
#ifdef CONFIG_XFRM
@@ -612,6 +617,9 @@ 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->skb_burst)
+ seq_printf(seq, " skb_burst: %d\n", pkt_dev->skb_burst);
+
if (pkt_dev->node >= 0)
seq_printf(seq, " node: %d\n", pkt_dev->node);
@@ -1120,6 +1128,16 @@ static ssize_t pktgen_if_write(struct file *file,
pkt_dev->dst_mac_count);
return count;
}
+ if (!strcmp(name, "skb_burst")) {
+ len = num_arg(&user_buffer[i], 10, &value);
+ if (len < 0)
+ return len;
+
+ i += len;
+ pkt_dev->skb_burst = value;
+ sprintf(pg_result, "OK: skb_burst=%d", pkt_dev->skb_burst);
+ return count;
+ }
if (!strcmp(name, "node")) {
len = num_arg(&user_buffer[i], 10, &value);
if (len < 0)
@@ -3165,6 +3183,7 @@ static int pktgen_stop_device(struct pktgen_dev *pkt_dev)
return -EINVAL;
}
+ // FIXME: Possibly missing a tailptr flush here...
pkt_dev->running = 0;
kfree_skb(pkt_dev->skb);
pkt_dev->skb = NULL;
@@ -3327,6 +3346,16 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
queue_map = skb_get_queue_mapping(pkt_dev->skb);
txq = netdev_get_tx_queue(odev, queue_map);
+ /* Do HW level bursting via skb->xmit_more */
+ if (pkt_dev->skb_burst > 0) {
+ if (pkt_dev->skb_burst_count++ < pkt_dev->skb_burst) {
+ pkt_dev->skb->xmit_more = 1;
+ } else {
+ pkt_dev->skb->xmit_more = 0;
+ pkt_dev->skb_burst_count = 1;
+ }
+ }
+
local_bh_disable();
HARD_TX_LOCK(odev, txq, smp_processor_id());
@@ -3337,7 +3366,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
goto unlock;
}
atomic_inc(&(pkt_dev->skb->users));
- ret = netdev_start_xmit(pkt_dev->skb, odev);
+ ret = odev->netdev_ops->ndo_start_xmit(pkt_dev->skb, odev);
+ //ret = netdev_start_xmit(pkt_dev->skb, odev);
switch (ret) {
case NETDEV_TX_OK:
@@ -3562,6 +3592,8 @@ 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->skb_burst = 0;
+ pkt_dev->skb_burst_count = 1;
pkt_dev->node = -1;
err = pktgen_setup_dev(t->net, pkt_dev, ifname);
--
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