From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net-next] neigh: reduce arp latency Date: Tue, 09 Aug 2011 17:40:34 +0200 Message-ID: <1312904434.2371.39.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev To: David Miller Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:59843 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753178Ab1HIPkh (ORCPT ); Tue, 9 Aug 2011 11:40:37 -0400 Received: by wyg24 with SMTP id 24so78785wyg.19 for ; Tue, 09 Aug 2011 08:40:36 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: 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 --- 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);