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c7d4426a98
linux/net
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Eric Dumazet c7d4426a98 net: introduce DST_NOCACHE flag 
While doing stress tests with IP route cache disabled, and multi queue
devices, I noticed a very high contention on one rwlock used in
neighbour code.

When many cpus are trying to send frames (possibly using a high
performance multiqueue device) to the same neighbour, they fight for the
neigh->lock rwlock in order to call neigh_hh_init(), and fight on
hh->hh_refcnt (a pair of atomic_inc/atomic_dec_and_test())

But we dont need to call neigh_hh_init() for dst that are used only
once. It costs four atomic operations at least, on two contended cache
lines, plus the high contention on neigh->lock rwlock.

Introduce a new dst flag, DST_NOCACHE, that is set when dst was not
inserted in route cache.

With the stress test bench, sending 160000000 frames on one neighbour,
results are :

Before patch:

real	2m28.406s
user	0m11.781s
sys	36m17.964s


After patch:

real	1m26.532s
user	0m12.185s
sys	20m3.903s

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2010-10-03 22:17:54 -07:00
..
9p net: return operator cleanup 2010-09-23 14:33:39 -07:00
802 net: return operator cleanup 2010-09-23 14:33:39 -07:00
8021q 8021q: Use netif_copy_real_num_queues() to set queue counts 2010-09-27 22:09:57 -07:00
appletalk
atm Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
ax25 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-09 22:27:33 -07:00
bluetooth net: return operator cleanup 2010-09-23 14:33:39 -07:00
bridge bridge : Sanitize skb before it enters the IP stack 2010-09-19 12:42:34 -07:00
caif caif: Use default send and receive buffer size in caif_socket. 2010-09-21 18:05:31 -07:00
can net: simplify flags for tx timestamping 2010-08-19 00:08:30 -07:00
core net: introduce DST_NOCACHE flag 2010-10-03 22:17:54 -07:00
dcb
dccp net: return operator cleanup 2010-09-23 14:33:39 -07:00
decnet net/decnet: Adjust confusing if indentation 2010-08-16 21:06:30 -07:00
dns_resolver DNS: If the DNS server returns an error, allow that to be cached [ver #2] 2010-08-11 17:11:28 +00:00
dsa phylib: available for any speed ethernet 2010-08-11 23:03:50 -07:00
econet net: return operator cleanup 2010-09-23 14:33:39 -07:00
ethernet net: return operator cleanup 2010-09-23 14:33:39 -07:00
ieee802154 ieee802154: Fix possible NULL pointer dereference in wpan_phy_alloc 2010-05-23 23:11:07 -07:00
ipv4 net: introduce DST_NOCACHE flag 2010-10-03 22:17:54 -07:00
ipv6 ip6tnl: percpu stats accounting 2010-09-29 13:25:52 -07:00
ipx
irda net: return operator cleanup 2010-09-23 14:33:39 -07:00
iucv net: use __packed annotation 2010-06-03 03:21:52 -07:00
key net: return operator cleanup 2010-09-23 14:33:39 -07:00
l2tp net: constify some ppp/pptp structs 2010-09-21 18:04:47 -07:00
lapb
llc net/llc: storing negative error codes in unsigned short 2010-09-16 22:38:23 -07:00
mac80211 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next-2.6 into for-davem 2010-10-01 11:12:36 -04:00
netfilter Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
netlabel net: Remove unnecessary returns from void function()s 2010-05-17 23:23:14 -07:00
netlink netlink: Make NETLINK_USERSOCK work again. 2010-08-31 09:51:37 -07:00
netrom
packet net: simplify flags for tx timestamping 2010-08-19 00:08:30 -07:00
phonet Phonet: restore flow control credits when sending fails 2010-09-30 17:57:30 -07:00
rds Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
rfkill net: return operator cleanup 2010-09-23 14:33:39 -07:00
rose Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
rxrpc Add a dummy printk function for the maintenance of unused printks 2010-08-12 09:51:35 -07:00
sched net: rename netdev rx_queue to ingress_queue 2010-09-29 13:25:53 -07:00
sctp sctp: Fix break indentation in sctp_ioctl(). 2010-10-03 22:14:37 -07:00
sunrpc Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
tipc net: return operator cleanup 2010-09-23 14:33:39 -07:00
unix Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-09 22:27:33 -07:00
wanrouter net: autoconvert trivial BKL users to private mutex 2010-07-12 20:21:47 -07:00
wimax Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6 2010-05-20 21:04:44 -07:00
wireless Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next-2.6 into for-davem 2010-10-01 11:12:36 -04:00
x25 X.25 remove bkl in poll 2010-09-22 13:35:51 -07:00
xfrm xfrm: Allow different selector family in temporary state 2010-09-20 11:11:38 -07:00
compat.c From abbffa2aa9bd6f8df16d0d0a102af677510d8b9a Mon Sep 17 00:00:00 2001 2010-06-03 20:03:40 -07:00
Kconfig net: RPS needs to depend upon USE_GENERIC_SMP_HELPERS 2010-09-14 21:42:22 -07:00
Makefile DNS: Separate out CIFS DNS Resolver code 2010-08-05 17:17:51 +00:00
nonet.c
socket.c net: remove address space warnings in net/socket.c 2010-09-08 13:46:13 -07:00
sysctl_net.c net: Remove unnecessary returns from void function()s 2010-05-17 23:23:14 -07:00
TUNABLE