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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lmc
.gitignore
c101.c
cosa.c
cosa.h
cycx_drv.c
cycx_main.c
cycx_x25.c
dlci.c
dscc4.c
farsync.c
farsync.h
hd64570.c
hd64570.h
hd64572.c
hd64572.h
hdlc_cisco.c
hdlc_fr.c	net: release dst entry in dev_hard_start_xmit()	2009-05-18 22:19:19 -07:00
hdlc_ppp.c
hdlc_raw_eth.c
hdlc_raw.c
hdlc_x25.c
hdlc.c
hostess_sv11.c
ixp4xx_hss.c
Kconfig
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pc300_drv.c
pc300_tty.c
pc300-falc-lh.h
pc300.h
pc300too.c
pci200syn.c
sbni.c
sbni.h
sdla.c
sealevel.c
wanxl.c
wanxl.h
wanxlfw.inc_shipped
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x25_asy.c
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z85230.c
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