IPIP tunnel performance improvement

PATCH In review zhao ya 2 participants 4 messages Feb 27, 2016 1 message not in the archive

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zhao ya

author

2016-02-27 04:40 UTC #1 lore raw

PATCH 1/1 IPIP tunnel performance improvement

From: Zhao Ya <[email protected]>
Date: Sat, 27 Feb 2016 10:06:44 +0800
Subject: [PATCH] IPIP tunnel performance improvement

bypass the logic of each packet's own neighbour creation when using pointopint or loopback device.

Recently, in our tests, met a performance problem.
In a large number of packets with different target IP address through ipip tunnel, PPS will decrease sharply.

The output of perf top are as follows, __write_lock_failed is of the first:
- 5.89% [kernel] [k] __write_lock_failed
-__write_lock_failed a
-_raw_write_lock_bh a
-__neigh_create a
-ip_finish_output a
-ip_output a
-ip_local_out a

The neighbour subsystem will create a neighbour object for each target when using pointopint device. When massive amounts of packets with diff- erent target IP address to be xmit through a pointopint device, these packets will suffer the bottleneck at write_lock_bh(&tbl->lock) after creating the neighbour object and then inserting it into a hash-table at the same time.

This patch correct it. Only one or little amounts of neighbour objects will be created when massive amounts of packets with different target IP address through ipip tunnel.

As the result, performance will be improved.

Signed-off-by Zhao Ya <[email protected]>

Signed-off-by Zhaoya <[email protected]>

---
 net/ipv4/ip_output.c | 2 ++
 1 file changed, 2 insertions(+)

net/ipv4/ip_output.c +2 -0

index 64878ef..d7c0594 100644
@@ -202,6 +202,8 @@ static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *s
 
 	rcu_read_lock_bh();
 	nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
+	if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
+		nexthop = 0;
 	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
 	if (unlikely(!neigh))
 		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);

zhao ya

author

2016-02-27 04:52 UTC #2 lore raw

BTW,before the version 3.5 kernel, the source code contains the logic. 2.6.32, for example, in arp_bind_neighbour function, there are the following logic:

__be32 nexthop = ((struct rtable *) DST) - > rt_gateway; if (dev - > flags & (IFF_LOOPBACK | IFF_POINTOPOINT)) nexthop = 0;
n = __neigh_lookup_errno (
...

zhao ya said, at 2/27/2016 12:40 PM:

Quoted 55 lines

From: Zhao Ya <[email protected]>
Date: Sat, 27 Feb 2016 10:06:44 +0800
Subject: [PATCH] IPIP tunnel performance improvement
bypass the logic of each packet's own neighbour creation when using pointopint or loopback device.
Recently, in our tests, met a performance problem.
In a large number of packets with different target IP address through ipip tunnel, PPS will decrease sharply.
The output of perf top are as follows, __write_lock_failed is of the first:
- 5.89% [kernel] [k] __write_lock_failed
-__write_lock_failed a
-_raw_write_lock_bh a
-__neigh_create a
-ip_finish_output a
-ip_output a
-ip_local_out a
The neighbour subsystem will create a neighbour object for each target when using pointopint device. When massive amounts of packets with diff- erent target IP address to be xmit through a pointopint device, these packets will suffer the bottleneck at write_lock_bh(&tbl->lock) after creating the neighbour object and then inserting it into a hash-table at the same time.
This patch correct it. Only one or little amounts of neighbour objects will be created when massive amounts of packets with different target IP address through ipip tunnel.
As the result, performance will be improved.
Signed-off-by Zhao Ya <[email protected]>
Signed-off-by Zhaoya <[email protected]>
---
 net/ipv4/ip_output.c | 2 ++
 1 file changed, 2 insertions(+)
net/ipv4/ip_output.c +2 -0
index 64878ef..d7c0594 100644
@@ -202,6 +202,8 @@ static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *s
 
 	rcu_read_lock_bh();
 	nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
+	if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
+		nexthop = 0;
 	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
 	if (unlikely(!neigh))
 		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);

Cong Wang

2016-02-27 06:29 UTC #3 lore raw

In reply to zhao ya

Quoted 27 lines · zhao ya

From: Zhao Ya <[email protected]>
Date: Sat, 27 Feb 2016 10:06:44 +0800
Subject: [PATCH] IPIP tunnel performance improvement
bypass the logic of each packet's own neighbour creation when using pointopint or loopback device.
Recently, in our tests, met a performance problem.
In a large number of packets with different target IP address through ipip tunnel, PPS will decrease sharply.
The output of perf top are as follows, __write_lock_failed is of the first:
- 5.89% [kernel] [k] __write_lock_failed
   -__write_lock_failed                                         a
   -_raw_write_lock_bh                                          a
   -__neigh_create                                              a
   -ip_finish_output                                            a
   -ip_output                                                   a
   -ip_local_out                                                a
The neighbour subsystem will create a neighbour object for each target when using pointopint device. When massive amounts of packets with diff- erent target IP address to be xmit through a pointopint device, these packets will suffer the bottleneck at write_lock_bh(&tbl->lock) after creating the neighbour object and then inserting it into a hash-table at the same time.

Quoted 5 lines

This patch correct it. Only one or little amounts of neighbour objects will be created when massive amounts of packets with different target IP address through ipip tunnel.
As the result, performance will be improved.

Well, you just basically revert another bug fix:

commit 0bb4087cbec0ef74fd416789d6aad67957063057

Author: David S. Miller <[email protected]>
Date:   Fri Jul 20 16:00:53 2012 -0700

ipv4: Fix neigh lookup keying over loopback/point-to-point devices.

We were using a special key "0" for all loopback and point-to-point device neigh lookups under ipv4, but we wouldn't use that special key for the neigh creation.

So basically we'd make a new neigh at each and every lookup :-)

This special case to use only one neigh for these device types is of dubious value, so just remove it entirely.

Reported-by Eric Dumazet <[email protected]>

Signed-off-by David S. Miller <[email protected]>

which would bring the neigh entries counting problem back...

Did you try to tune the neigh gc parameters for your case?

Thanks.

zhao ya

author

2016-02-27 07:06 UTC #4 lore raw

Yes, I did, but have no effect.

I want to ask is, why David's patch not used.

Thanks.

Cong Wang said, at 2/27/2016 2:29 PM:

Quoted 60 lines · zhao ya

Quoted 27 lines
From: Zhao Ya <[email protected]>
Date: Sat, 27 Feb 2016 10:06:44 +0800
Subject: [PATCH] IPIP tunnel performance improvement
bypass the logic of each packet's own neighbour creation when using pointopint or loopback device.
Recently, in our tests, met a performance problem.
In a large number of packets with different target IP address through ipip tunnel, PPS will decrease sharply.
The output of perf top are as follows, __write_lock_failed is of the first:
- 5.89% [kernel] [k] __write_lock_failed
   -__write_lock_failed                                         a
   -_raw_write_lock_bh                                          a
   -__neigh_create                                              a
   -ip_finish_output                                            a
   -ip_output                                                   a
   -ip_local_out                                                a
The neighbour subsystem will create a neighbour object for each target when using pointopint device. When massive amounts of packets with diff- erent target IP address to be xmit through a pointopint device, these packets will suffer the bottleneck at write_lock_bh(&tbl->lock) after creating the neighbour object and then inserting it into a hash-table at the same time.
Quoted 5 lines
This patch correct it. Only one or little amounts of neighbour objects will be created when massive amounts of packets with different target IP address through ipip tunnel.
As the result, performance will be improved.
Well, you just basically revert another bug fix:
commit 0bb4087cbec0ef74fd416789d6aad67957063057
Author: David S. Miller <[email protected]>
Date:   Fri Jul 20 16:00:53 2012 -0700
ipv4: Fix neigh lookup keying over loopback/point-to-point devices.
We were using a special key "0" for all loopback and point-to-point device neigh lookups under ipv4, but we wouldn't use that special key for the neigh creation.
So basically we'd make a new neigh at each and every lookup :-)
This special case to use only one neigh for these device types is of dubious value, so just remove it entirely.
Reported-by Eric Dumazet <[email protected]>
Signed-off-by David S. Miller <[email protected]>
which would bring the neigh entries counting problem back...
Did you try to tune the neigh gc parameters for your case?
Thanks.