* [PATCH] ip6tnl: avoid touching dst refcount in ip6_tnl_xmit2()
@ 2011-07-28 14:32 Eric Dumazet
2011-08-01 8:56 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Eric Dumazet @ 2011-07-28 14:32 UTC (permalink / raw)
To: David Miller; +Cc: netdev
Even using percpu stats, we still hit tunnel dst_entry refcount in
ip6_tnl_xmit2()
Since we are in RCU locked section, we can use skb_dst_set_noref() and
avoid these atomic operations, leaving dst shared on cpus.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
net/ipv6/ip6_tunnel.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 0bc9888..6fb1fb3 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -889,7 +889,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
struct net_device_stats *stats = &t->dev->stats;
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
struct ipv6_tel_txoption opt;
- struct dst_entry *dst;
+ struct dst_entry *dst, *ndst = NULL;
struct net_device *tdev;
int mtu;
unsigned int max_headroom = sizeof(struct ipv6hdr);
@@ -897,19 +897,19 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
int err = -1;
int pkt_len;
- if ((dst = ip6_tnl_dst_check(t)) != NULL)
- dst_hold(dst);
- else {
- dst = ip6_route_output(net, NULL, fl6);
+ dst = ip6_tnl_dst_check(t);
+ if (!dst) {
+ ndst = ip6_route_output(net, NULL, fl6);
- if (dst->error)
+ if (ndst->error)
goto tx_err_link_failure;
- dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), NULL, 0);
- if (IS_ERR(dst)) {
- err = PTR_ERR(dst);
- dst = NULL;
+ ndst = xfrm_lookup(net, ndst, flowi6_to_flowi(fl6), NULL, 0);
+ if (IS_ERR(ndst)) {
+ err = PTR_ERR(ndst);
+ ndst = NULL;
goto tx_err_link_failure;
}
+ dst = ndst;
}
tdev = dst->dev;
@@ -955,7 +955,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
skb = new_skb;
}
skb_dst_drop(skb);
- skb_dst_set(skb, dst_clone(dst));
+ skb_dst_set_noref(skb, dst);
skb->transport_header = skb->network_header;
@@ -987,13 +987,14 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
stats->tx_errors++;
stats->tx_aborted_errors++;
}
- ip6_tnl_dst_store(t, dst);
+ if (ndst)
+ ip6_tnl_dst_store(t, ndst);
return 0;
tx_err_link_failure:
stats->tx_carrier_errors++;
dst_link_failure(skb);
tx_err_dst_release:
- dst_release(dst);
+ dst_release(ndst);
return err;
}
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] ip6tnl: avoid touching dst refcount in ip6_tnl_xmit2()
2011-07-28 14:32 [PATCH] ip6tnl: avoid touching dst refcount in ip6_tnl_xmit2() Eric Dumazet
@ 2011-08-01 8:56 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2011-08-01 8:56 UTC (permalink / raw)
To: eric.dumazet; +Cc: netdev
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 28 Jul 2011 16:32:25 +0200
> Even using percpu stats, we still hit tunnel dst_entry refcount in
> ip6_tnl_xmit2()
>
> Since we are in RCU locked section, we can use skb_dst_set_noref() and
> avoid these atomic operations, leaving dst shared on cpus.
>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Queued up for net-next
^ permalink raw reply [flat|nested] 2+ messages in thread
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