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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
..
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
af_inet.c net: build_ehash_secret() and rt_bind_peer() cleanups 2010-08-20 00:50:16 -07:00
ah4.c
arp.c arp: remove unnecessary export of arp_broken_ops 2010-09-29 19:45:35 -07:00
cipso_ipv4.c
datagram.c net: return operator cleanup 2010-09-23 14:33:39 -07:00
devinet.c ipv4: ip_ptr cleanups 2010-09-15 22:06:05 -07:00
esp4.c
fib_frontend.c ipv4: introduce __ip_dev_find() 2010-09-30 21:16:05 -07:00
fib_hash.c
fib_lookup.h
fib_rules.c
fib_semantics.c
fib_trie.c fib: cleanups 2010-09-10 12:32:02 -07:00
gre.c gre: protocol table can be static 2010-10-03 21:50:51 -07:00
icmp.c net: simplify flags for tx timestamping 2010-08-19 00:08:30 -07:00
igmp.c ipv4: force_igmp_version ignored when a IGMPv3 query received 2010-09-13 12:56:51 -07:00
inet_connection_sock.c net/ipv4: EXPORT_SYMBOL cleanups 2010-07-12 12:57:54 -07:00
inet_diag.c net: return operator cleanup 2010-09-23 14:33:39 -07:00
inet_fragment.c net/ipv4: EXPORT_SYMBOL cleanups 2010-07-12 12:57:54 -07:00
inet_hashtables.c net/ipv4: EXPORT_SYMBOL cleanups 2010-07-12 12:57:54 -07:00
inet_lro.c
inet_timewait_sock.c
inetpeer.c inetpeer: restore small inet_peer structures 2010-06-16 11:55:39 -07:00
ip_forward.c net-next: remove useless union keyword 2010-06-10 23:31:35 -07:00
ip_fragment.c net: return operator cleanup 2010-09-23 14:33:39 -07:00
ip_gre.c ip_gre: comments change 2010-09-29 23:35:10 -07:00
ip_input.c net: use this_cpu_ptr() 2010-06-28 23:24:29 -07:00
ip_options.c bridge : Sanitize skb before it enters the IP stack 2010-09-19 12:42:34 -07:00
ip_output.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
ip_sockglue.c ipv4: enable getsockopt() for IP_NODEFRAG 2010-09-13 19:57:23 -07:00
ipcomp.c
ipconfig.c
ipip.c ipip: enable lockless xmits 2010-09-29 13:25:44 -07:00
ipmr.c ipmr: cleanups 2010-10-03 21:50:53 -07:00
Kconfig Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-09 22:27:33 -07:00
Makefile PPTP: PPP over IPv4 (Point-to-Point Tunneling Protocol) 2010-08-21 23:05:39 -07:00
netfilter.c Merge branch 'master' of /repos/git/net-next-2.6 2010-06-15 17:31:06 +02:00
proc.c snmp: 64bit ipstats_mib for all arches 2010-06-30 13:31:19 -07:00
protocol.c net: inet_add_protocol() can use cmpxchg() 2010-09-08 21:31:35 -07:00
raw.c net: simplify flags for tx timestamping 2010-08-19 00:08:30 -07:00
route.c net: introduce DST_NOCACHE flag 2010-10-03 22:17:54 -07:00
syncookies.c syncookies: add support for ECN 2010-06-26 22:00:03 -07:00
sysctl_net_ipv4.c
tcp_bic.c
tcp_cong.c net/ipv4: Eliminate kstrdup memory leak 2010-08-27 19:31:56 -07:00
tcp_cubic.c
tcp_diag.c
tcp_highspeed.c
tcp_htcp.c
tcp_hybla.c
tcp_illinois.c
tcp_input.c tcp: tcp_enter_quickack_mode can be static 2010-09-29 19:45:36 -07:00
tcp_ipv4.c gro: unexport tcp4_gro_receive and tcp4_gro_complete 2010-08-31 13:37:07 -07:00
tcp_lp.c
tcp_minisocks.c net: return operator cleanup 2010-09-23 14:33:39 -07:00
tcp_output.c net: return operator cleanup 2010-09-23 14:33:39 -07:00
tcp_probe.c
tcp_scalable.c
tcp_timer.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-09 22:27:33 -07:00
tcp_vegas.c
tcp_vegas.h
tcp_veno.c
tcp_westwood.c net: return operator cleanup 2010-09-23 14:33:39 -07:00
tcp_yeah.c
tcp.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-27 01:03:03 -07:00
tunnel4.c tunnels: missing rcu_assign_pointer() 2010-09-09 15:02:39 -07:00
udp_impl.h
udp.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-09-09 22:27:33 -07:00
udplite.c net/ipv4: EXPORT_SYMBOL cleanups 2010-07-12 12:57:54 -07:00
xfrm4_input.c net/ipv4: EXPORT_SYMBOL cleanups 2010-07-12 12:57:54 -07:00
xfrm4_mode_beet.c
xfrm4_mode_transport.c
xfrm4_mode_tunnel.c
xfrm4_output.c
xfrm4_policy.c xfrm4: strip ECN bits from tos field 2010-09-22 20:25:48 -07:00
xfrm4_state.c xfrm: Allow different selector family in temporary state 2010-09-20 11:11:38 -07:00
xfrm4_tunnel.c net: struct xfrm_tunnel in read_mostly section 2010-08-30 13:50:45 -07:00