Eric Dumazet 93f154b594 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>		2009-05-18 22:19:19 -07:00
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datagram.c
dev_mcast.c
dev.c	net: release dst entry in dev_hard_start_xmit()	2009-05-18 22:19:19 -07:00
drop_monitor.c
dst.c
ethtool.c
fib_rules.c
filter.c
flow.c
gen_estimator.c
gen_stats.c
iovec.c
kmap_skb.h
link_watch.c
Makefile
neighbour.c
net_namespace.c
net-sysfs.c
net-sysfs.h
net-traces.c
netevent.c
netpoll.c
pktgen.c
request_sock.c
rtnetlink.c
scm.c
skb_dma_map.c
skbuff.c
sock.c
stream.c
sysctl_net_core.c
user_dma.c
utils.c