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Message-ID: <1312904434.2371.39.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date: Tue, 09 Aug 2011 17:40:34 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] neigh: reduce arp latency
Remove the artificial HZ latency on arp resolution.
Instead of firing a timer in one jiffy (up to 10 ms if HZ=100), lets
send the ARP message immediately.
Before patch :
# arp -d 192.168.20.108 ; ping -c 3 192.168.20.108
PING 192.168.20.108 (192.168.20.108) 56(84) bytes of data.
64 bytes from 192.168.20.108: icmp_seq=1 ttl=64 time=9.91 ms
64 bytes from 192.168.20.108: icmp_seq=2 ttl=64 time=0.065 ms
64 bytes from 192.168.20.108: icmp_seq=3 ttl=64 time=0.061 ms
After patch :
$ arp -d 192.168.20.108 ; ping -c 3 192.168.20.108
PING 192.168.20.108 (192.168.20.108) 56(84) bytes of data.
64 bytes from 192.168.20.108: icmp_seq=1 ttl=64 time=0.152 ms
64 bytes from 192.168.20.108: icmp_seq=2 ttl=64 time=0.064 ms
64 bytes from 192.168.20.108: icmp_seq=3 ttl=64 time=0.074 ms
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
net/core/neighbour.c | 32 ++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 8fab9b0..d99f908 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -844,6 +844,19 @@ static void neigh_invalidate(struct neighbour *neigh)
skb_queue_purge(&neigh->arp_queue);
}
+static void neigh_probe(struct neighbour *neigh)
+ __releases(neigh->lock)
+{
+ struct sk_buff *skb = skb_peek(&neigh->arp_queue);
+ /* keep skb alive even if arp_queue overflows */
+ if (skb)
+ skb = skb_copy(skb, GFP_ATOMIC);
+ write_unlock(&neigh->lock);
+ neigh->ops->solicit(neigh, skb);
+ atomic_inc(&neigh->probes);
+ kfree_skb(skb);
+}
+
/* Called when a timer expires for a neighbour entry. */
static void neigh_timer_handler(unsigned long arg)
@@ -920,14 +933,7 @@ static void neigh_timer_handler(unsigned long arg)
neigh_hold(neigh);
}
if (neigh->nud_state & (NUD_INCOMPLETE | NUD_PROBE)) {
- struct sk_buff *skb = skb_peek(&neigh->arp_queue);
- /* keep skb alive even if arp_queue overflows */
- if (skb)
- skb = skb_copy(skb, GFP_ATOMIC);
- write_unlock(&neigh->lock);
- neigh->ops->solicit(neigh, skb);
- atomic_inc(&neigh->probes);
- kfree_skb(skb);
+ neigh_probe(neigh);
} else {
out:
write_unlock(&neigh->lock);
@@ -943,6 +949,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
{
int rc;
unsigned long now;
+ bool immediate_probe = false;
write_lock_bh(&neigh->lock);
@@ -957,7 +964,8 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
atomic_set(&neigh->probes, neigh->parms->ucast_probes);
neigh->nud_state = NUD_INCOMPLETE;
neigh->updated = jiffies;
- neigh_add_timer(neigh, now + 1);
+ neigh_add_timer(neigh, now + HZ);
+ immediate_probe = true;
} else {
neigh->nud_state = NUD_FAILED;
neigh->updated = jiffies;
@@ -989,7 +997,11 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
rc = 1;
}
out_unlock_bh:
- write_unlock_bh(&neigh->lock);
+ if (immediate_probe)
+ neigh_probe(neigh);
+ else
+ write_unlock(&neigh->lock);
+ local_bh_enable();
return rc;
}
EXPORT_SYMBOL(__neigh_event_send);
--
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