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authorEric Dumazet <dada1@cosmosbay.com>2009-05-18 22:19:19 -0700
committerDavid S. Miller <davem@davemloft.net>2009-05-18 22:19:19 -0700
commit93f154b594fe47e4a7e5358b309add449a046cd3 (patch)
tree479d9f2db25922a2312547c97e73d5a11b68bb1c
parent496a60cdcd5d0d884dddf6c3b4ea912923a70f13 (diff)
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net: release dst entry in dev_hard_start_xmit()
One point of contention in high network loads is the dst_release() performed when a transmited skb is freed. This is because NIC tx completion calls dev_kree_skb() long after original call to dev_queue_xmit(skb). CPU cache is cold and the atomic op in dst_release() stalls. On SMP, this is quite visible if one CPU is 100% handling softirqs for a network device, since dst_clone() is done by other cpus, involving cache line ping pongs. It seems right place to release dst is in dev_hard_start_xmit(), for most devices but ones that are virtual, and some exceptions. David Miller suggested to define a new device flag, set in alloc_netdev_mq() (so that most devices set it at init time), and carefuly unset in devices which dont want a NULL skb->dst in their ndo_start_xmit(). List of devices that must clear this flag is : - loopback device, because it calls netif_rx() and quoting Patrick : "ip_route_input() doesn't accept loopback addresses, so loopback packets already need to have a dst_entry attached." - appletalk/ipddp.c : needs skb->dst in its xmit function - And all devices that call again dev_queue_xmit() from their xmit function (as some classifiers need skb->dst) : bonding, vlan, macvlan, eql, ifb, hdlc_fr Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/appletalk/ipddp.c1
-rw-r--r--drivers/net/bonding/bond_main.c1
-rw-r--r--drivers/net/eql.c1
-rw-r--r--drivers/net/ifb.c1
-rw-r--r--drivers/net/loopback.c1
-rw-r--r--drivers/net/macvlan.c1
-rw-r--r--drivers/net/wan/hdlc_fr.c1
-rw-r--r--include/linux/if.h3
-rw-r--r--net/8021q/vlan_dev.c1
-rw-r--r--net/core/dev.c9
10 files changed, 20 insertions, 0 deletions
diff --git a/drivers/net/appletalk/ipddp.c b/drivers/net/appletalk/ipddp.c
index da64ba88d7f..f939e92fcf8 100644
--- a/drivers/net/appletalk/ipddp.c
+++ b/drivers/net/appletalk/ipddp.c
@@ -71,6 +71,7 @@ static struct net_device * __init ipddp_init(void)
if (!dev)
return ERR_PTR(-ENOMEM);
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
strcpy(dev->name, "ipddp%d");
if (version_printed++ == 0)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 96d7689995c..92a9d69c565 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5148,6 +5148,7 @@ int bond_create(char *name, struct bond_params *params)
goto out_rtnl;
}
+ bond_dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
if (!name) {
res = dev_alloc_name(bond_dev, "bond%d");
if (res < 0)
diff --git a/drivers/net/eql.c b/drivers/net/eql.c
index 5210bb1027c..19b7dd98394 100644
--- a/drivers/net/eql.c
+++ b/drivers/net/eql.c
@@ -194,6 +194,7 @@ static void __init eql_setup(struct net_device *dev)
dev->type = ARPHRD_SLIP;
dev->tx_queue_len = 5; /* Hands them off fast */
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
}
static int eql_open(struct net_device *dev)
diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 60a26300193..96713ef0629 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -156,6 +156,7 @@ static void ifb_setup(struct net_device *dev)
dev->flags |= IFF_NOARP;
dev->flags &= ~IFF_MULTICAST;
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
random_ether_addr(dev->dev_addr);
}
diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 6f71157bea8..da472c68748 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -170,6 +170,7 @@ static void loopback_setup(struct net_device *dev)
dev->tx_queue_len = 0;
dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
dev->flags = IFF_LOOPBACK;
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
| NETIF_F_TSO
| NETIF_F_NO_CSUM
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 329cd50d0e2..d5334b41e4b 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -414,6 +414,7 @@ static void macvlan_setup(struct net_device *dev)
{
ether_setup(dev);
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
dev->netdev_ops = &macvlan_netdev_ops;
dev->destructor = free_netdev;
dev->header_ops = &macvlan_hard_header_ops,
diff --git a/drivers/net/wan/hdlc_fr.c b/drivers/net/wan/hdlc_fr.c
index 80053010109..bfa0161a02d 100644
--- a/drivers/net/wan/hdlc_fr.c
+++ b/drivers/net/wan/hdlc_fr.c
@@ -1054,6 +1054,7 @@ static void pvc_setup(struct net_device *dev)
dev->flags = IFF_POINTOPOINT;
dev->hard_header_len = 10;
dev->addr_len = 2;
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
}
static const struct net_device_ops pvc_ops = {
diff --git a/include/linux/if.h b/include/linux/if.h
index 1108f3e099e..b9a6229f3be 100644
--- a/include/linux/if.h
+++ b/include/linux/if.h
@@ -67,6 +67,9 @@
#define IFF_ISATAP 0x80 /* ISATAP interface (RFC4214) */
#define IFF_MASTER_ARPMON 0x100 /* bonding master, ARP mon in use */
#define IFF_WAN_HDLC 0x200 /* WAN HDLC device */
+#define IFF_XMIT_DST_RELEASE 0x400 /* dev_hard_start_xmit() is allowed to
+ * release skb->dst
+ */
#define IF_GET_IFACE 0x0001 /* for querying only */
#define IF_GET_PROTO 0x0002
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 8faacee6863..ff7572ac548 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -739,6 +739,7 @@ void vlan_setup(struct net_device *dev)
ether_setup(dev);
dev->priv_flags |= IFF_802_1Q_VLAN;
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
dev->tx_queue_len = 0;
dev->netdev_ops = &vlan_netdev_ops;
diff --git a/net/core/dev.c b/net/core/dev.c
index 6d3630d1627..92ebeca2990 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1688,6 +1688,14 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
goto gso;
}
+ /*
+ * If device doesnt need skb->dst, release it right now while
+ * its hot in this cpu cache
+ */
+ if ((dev->priv_flags & IFF_XMIT_DST_RELEASE) && skb->dst) {
+ dst_release(skb->dst);
+ skb->dst = NULL;
+ }
rc = ops->ndo_start_xmit(skb, dev);
/*
* TODO: if skb_orphan() was called by
@@ -5045,6 +5053,7 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
netdev_init_queues(dev);
INIT_LIST_HEAD(&dev->napi_list);
+ dev->priv_flags = IFF_XMIT_DST_RELEASE;
setup(dev);
strcpy(dev->name, name);
return dev;