From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net-next] macvlan: add a salt to mc_hash() Date: Thu, 07 Feb 2013 18:41:02 -0800 Message-ID: <1360291262.28557.89.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev , Maciej =?UTF-8?Q?=C5=BBenczykowski?= To: David Miller Return-path: Received: from mail-oa0-f42.google.com ([209.85.219.42]:45368 "EHLO mail-oa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759207Ab3BHClG (ORCPT ); Thu, 7 Feb 2013 21:41:06 -0500 Received: by mail-oa0-f42.google.com with SMTP id i18so3612451oag.1 for ; Thu, 07 Feb 2013 18:41:04 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: =46rom: Eric Dumazet Some multicast addresses are common to all macvlans, so if a multicast message has a hash value collision, we have to deliver a copy to all macvlans, adding significant latency and possible packet drops if netdev_max_backlog limit is hit. Having a per macvlan hash function permits to reduce the impact of hash collisions. Suggested-by: Maciej =C5=BBenczykowski Signed-off-by: Eric Dumazet --- Should be applied after=20 "macvlan: broadcast addr should be part of mc_filter" drivers/net/macvlan.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c index ce7c926..e4b8078 100644 --- a/drivers/net/macvlan.c +++ b/drivers/net/macvlan.c @@ -127,10 +127,18 @@ static int macvlan_broadcast_one(struct sk_buff *= skb, return vlan->receive(skb); } =20 -static unsigned int mc_hash(const unsigned char *addr) +static u32 macvlan_hash_mix(const struct macvlan_dev *vlan) +{ + return (u32)(((unsigned long)vlan) >> L1_CACHE_SHIFT); +} + + +static unsigned int mc_hash(const struct macvlan_dev *vlan, + const unsigned char *addr) { u32 val =3D __get_unaligned_cpu32(addr + 2); =20 + val ^=3D macvlan_hash_mix(vlan); return hash_32(val, MACVLAN_MC_FILTER_BITS); } =20 @@ -145,7 +153,7 @@ static void macvlan_broadcast(struct sk_buff *skb, struct sk_buff *nskb; unsigned int i; int err; - unsigned int hash =3D mc_hash(eth->h_dest); + unsigned int hash; =20 if (skb->protocol =3D=3D htons(ETH_P_PAUSE)) return; @@ -155,6 +163,7 @@ static void macvlan_broadcast(struct sk_buff *skb, if (vlan->dev =3D=3D src || !(vlan->mode & mode)) continue; =20 + hash =3D mc_hash(vlan, eth->h_dest); if (!test_bit(hash, vlan->mc_filter)) continue; nskb =3D skb_clone(skb, GFP_ATOMIC); @@ -424,10 +433,10 @@ static void macvlan_set_mac_lists(struct net_devi= ce *dev) =20 bitmap_zero(filter, MACVLAN_MC_FILTER_SZ); netdev_for_each_mc_addr(ha, dev) { - __set_bit(mc_hash(ha->addr), filter); + __set_bit(mc_hash(vlan, ha->addr), filter); } =20 - __set_bit(mc_hash(dev->broadcast), filter); + __set_bit(mc_hash(vlan, dev->broadcast), filter); =20 bitmap_copy(vlan->mc_filter, filter, MACVLAN_MC_FILTER_SZ); }