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Eric Dumazet 3b098e2d7c net: Consistent skb timestamping 
With RPS inclusion, skb timestamping is not consistent in RX path.

If netif_receive_skb() is used, its deferred after RPS dispatch.

If netif_rx() is used, its done before RPS dispatch.

This can give strange tcpdump timestamps results.

I think timestamping should be done as soon as possible in the receive
path, to get meaningful values (ie timestamps taken at the time packet
was delivered by NIC driver to our stack), even if NAPI already can
defer timestamping a bit (RPS can help to reduce the gap)

Tom Herbert prefer to sample timestamps after RPS dispatch. In case
sampling is expensive (HPET/acpi_pm on x86), this makes sense.

Let admins switch from one mode to another, using a new
sysctl, /proc/sys/net/core/netdev_tstamp_prequeue

Its default value (1), means timestamps are taken as soon as possible,
before backlog queueing, giving accurate timestamps.

Setting a 0 value permits to sample timestamps when processing backlog,
after RPS dispatch, to lower the load of the pre-RPS cpu.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2010-05-15 23:57:10 -07:00
..
9p Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs 2010-04-05 13:42:54 -07:00
802 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-11 14:53:53 -07:00
8021q Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-11 14:53:53 -07:00
appletalk Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-11 14:53:53 -07:00
atm net: sock_def_readable() and friends RCU conversion 2010-05-01 15:00:15 -07:00
ax25 net: sk_sleep() helper 2010-04-20 16:37:13 -07:00
bluetooth Bluetooth: Fix issues where sk_sleep() helper is needed now 2010-05-10 11:33:10 +02:00
bridge bridge: update sysfs link names if port device names have changed 2010-05-15 23:10:15 -07:00
caif Bugfix: Link selection was swapped in switch. 2010-04-28 12:55:15 -07:00
can can: avoids a false warning 2010-04-13 03:03:14 -07:00
core net: Consistent skb timestamping 2010-05-15 23:57:10 -07:00
dcb include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
dccp net: sock_def_readable() and friends RCU conversion 2010-05-01 15:00:15 -07:00
decnet Merge branch 'master' of /repos/git/net-next-2.6 2010-05-10 18:39:28 +02:00
dsa Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-11 14:53:53 -07:00
econet include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
ethernet net: Inline skb_pull() in eth_type_trans(). 2010-05-02 02:21:44 -07:00
ieee802154 ieee802154: Fix oops during ieee802154_sock_ioctl 2010-04-26 11:20:32 -07:00
ipv4 net: reserve ports for applications using fixed port numbers 2010-05-15 23:28:40 -07:00
ipv6 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/kaber/nf-next-2.6 2010-05-13 14:14:10 -07:00
ipx include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
irda net: sk_sleep() helper 2010-04-20 16:37:13 -07:00
iucv net: sock_def_readable() and friends RCU conversion 2010-05-01 15:00:15 -07:00
key include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
l2tp l2tp_eth: fix memory allocation 2010-04-23 16:37:33 -07:00
lapb include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
llc Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-05-12 00:05:35 -07:00
mac80211 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-05-12 00:05:35 -07:00
netfilter netfilter: xt_TEE depends on NF_CONNTRACK 2010-05-14 13:52:30 -07:00
netlabel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-06 08:34:06 -07:00
netlink Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-11 14:53:53 -07:00
netrom net: sk_sleep() helper 2010-04-20 16:37:13 -07:00
packet Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-21 01:14:25 -07:00
phonet net: sock_def_readable() and friends RCU conversion 2010-05-01 15:00:15 -07:00
rds Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-27 12:49:13 -07:00
rfkill Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-11 14:53:53 -07:00
rose net: sk_sleep() helper 2010-04-20 16:37:13 -07:00
rxrpc net: sock_def_readable() and friends RCU conversion 2010-05-01 15:00:15 -07:00
sched Merge branch 'master' of git://dev.medozas.de/linux 2010-05-11 18:59:21 +02:00
sctp net: reserve ports for applications using fixed port numbers 2010-05-15 23:28:40 -07:00
sunrpc Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-05-12 00:05:35 -07:00
tipc tipc: Reduce footprint by un-inlining tipc_msg_* routines 2010-05-12 23:02:29 -07:00
unix unix/garbage: kill copy of the skb queue walker 2010-05-03 15:39:58 -07:00
wanrouter headers: smp_lock.h redux 2009-07-12 12:22:34 -07:00
wimax wimax: checking ERR_PTR vs null 2010-05-11 14:09:10 -07:00
wireless Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next-2.6 into for-davem 2010-05-11 14:24:55 -04:00
x25 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-04-27 12:49:13 -07:00
xfrm xfrm: fix policy unreferencing on larval drop 2010-05-15 23:49:26 -07:00
Kconfig l2tp: Split pppol2tp patch into separate l2tp and ppp parts 2010-04-03 14:56:02 -07:00
Makefile l2tp: Split pppol2tp patch into separate l2tp and ppp parts 2010-04-03 14:56:02 -07:00
TUNABLE
…
compat.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
nonet.c
…
socket.c net: sock_def_readable() and friends RCU conversion 2010-05-01 15:00:15 -07:00
sysctl_net.c net: spread __net_init, __net_exit 2010-01-17 19:16:02 -08:00