From 3807ff5899f892abb4f06747c245fd648a2acdc5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 7 Feb 2013 16:41:02 +0000 Subject: [PATCH] macvlan: add a salt to mc_hash() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Żenczykowski Signed-off-by: Eric Dumazet Signed-off-by: Maciej Żenczykowski Signed-off-by: David S. Miller --- 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 ce7c9268c740..e4b8078e88a9 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); } -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 = __get_unaligned_cpu32(addr + 2); + val ^= macvlan_hash_mix(vlan); return hash_32(val, MACVLAN_MC_FILTER_BITS); } @@ -145,7 +153,7 @@ static void macvlan_broadcast(struct sk_buff *skb, struct sk_buff *nskb; unsigned int i; int err; - unsigned int hash = mc_hash(eth->h_dest); + unsigned int hash; if (skb->protocol == htons(ETH_P_PAUSE)) return; @@ -155,6 +163,7 @@ static void macvlan_broadcast(struct sk_buff *skb, if (vlan->dev == src || !(vlan->mode & mode)) continue; + hash = mc_hash(vlan, eth->h_dest); if (!test_bit(hash, vlan->mc_filter)) continue; nskb = skb_clone(skb, GFP_ATOMIC); @@ -424,10 +433,10 @@ static void macvlan_set_mac_lists(struct net_device *dev) 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); } - __set_bit(mc_hash(dev->broadcast), filter); + __set_bit(mc_hash(vlan, dev->broadcast), filter); bitmap_copy(vlan->mc_filter, filter, MACVLAN_MC_FILTER_SZ); } -- GitLab