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authorEric Dumazet <eric.dumazet@gmail.com>2011-08-09 08:15:58 +0000
committerDavid S. Miller <davem@davemloft.net>2011-08-12 02:55:28 -0700
commitcd28ca0a3dd17c68d24b839602a0e6268ad28b5d (patch)
tree3e77945743e2c74c36b6942ad5bfe46a07eb9caa
parentbenet: fix build error on 32bit arch (diff)
downloadlinux-dev-cd28ca0a3dd17c68d24b839602a0e6268ad28b5d.tar.xz
linux-dev-cd28ca0a3dd17c68d24b839602a0e6268ad28b5d.zip
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@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/core/neighbour.c40
1 files changed, 26 insertions, 14 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 8fab9b0bb203..4002261f20d1 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);
@@ -942,7 +948,7 @@ out:
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);
@@ -950,14 +956,16 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
if (neigh->nud_state & (NUD_CONNECTED | NUD_DELAY | NUD_PROBE))
goto out_unlock_bh;
- now = jiffies;
-
if (!(neigh->nud_state & (NUD_STALE | NUD_INCOMPLETE))) {
if (neigh->parms->mcast_probes + neigh->parms->app_probes) {
+ unsigned long next, now = jiffies;
+
atomic_set(&neigh->probes, neigh->parms->ucast_probes);
neigh->nud_state = NUD_INCOMPLETE;
- neigh->updated = jiffies;
- neigh_add_timer(neigh, now + 1);
+ neigh->updated = now;
+ next = now + max(neigh->parms->retrans_time, HZ/2);
+ neigh_add_timer(neigh, next);
+ 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);