linux/net/core
Eric Dumazet ef711cf1d1 net: speedup dst_release()
During tbench/oprofile sessions, I found that dst_release() was in third position.

CPU: Core 2, speed 2999.68 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        symbol name
483726    9.0185  __copy_user_zeroing_intel
191466    3.5697  __copy_user_intel
185475    3.4580  dst_release
175114    3.2648  ip_queue_xmit
153447    2.8608  tcp_sendmsg
108775    2.0280  tcp_recvmsg
102659    1.9140  sysenter_past_esp
101450    1.8914  tcp_current_mss
95067     1.7724  __copy_from_user_ll
86531     1.6133  tcp_transmit_skb

Of course, all CPUS fight on the dst_entry associated with 127.0.0.1 

Instead of first checking the refcount value, then decrement it,
we use atomic_dec_return() to help CPU to make the right memory transaction
(ie getting the cache line in exclusive mode)

dst_release() is now at the fifth position, and tbench a litle bit faster ;)

CPU: Core 2, speed 3000.1 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        symbol name
647107    8.8072  __copy_user_zeroing_intel
258840    3.5229  ip_queue_xmit
258302    3.5155  __copy_user_intel
209629    2.8531  tcp_sendmsg
165632    2.2543  dst_release
149232    2.0311  tcp_current_mss
147821    2.0119  tcp_recvmsg
137893    1.8767  sysenter_past_esp
127473    1.7349  __copy_from_user_ll
121308    1.6510  ip_finish_output
118510    1.6129  tcp_transmit_skb
109295    1.4875  tcp_v4_rcv

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-11-14 00:53:54 -08:00
..
datagram.c net: sk_free_datagram() should use sk_mem_reclaim_partial() 2008-11-05 01:38:06 -08:00
dev_mcast.c net: Rationalise email address: Network Specific Parts 2008-10-13 19:01:08 -07:00
dev.c net: Guaranetee the proper ordering of the loopback device. v2 2008-11-07 22:54:20 -08:00
dst.c net: speedup dst_release() 2008-11-14 00:53:54 -08:00
ethtool.c netdev: Add support for rx flow hash configuration, using ethtool. 2008-07-02 03:47:41 -07:00
fib_rules.c net: fib_rules ordering fixes. 2008-11-07 22:52:34 -08:00
filter.c net: Tyop of sk_filter() comment 2008-07-01 19:55:40 -07:00
flow.c net: mark flow_cache_cpu_prepare() as __init 2008-11-06 23:06:44 -08:00
gen_estimator.c Revert "pkt_sched: Protect gen estimators under est_lock." 2008-08-18 22:32:10 -07:00
gen_stats.c [NET_SCHED]: Convert packet schedulers from rtnetlink to new netlink API 2008-01-28 15:11:10 -08:00
iovec.c net: Use standard structures for generic socket address structures. 2008-07-19 22:35:47 -07:00
kmap_skb.h [PATCH] severing skbuff.h -> highmem.h 2006-12-04 02:00:29 -05:00
link_watch.c net: Clean up explicit ->tx_queue references in link watch. 2008-07-08 23:01:06 -07:00
Makefile net: Add SKB DMA mapping helper functions. 2008-09-11 04:51:14 -07:00
neighbour.c net: Cleanup of neighbour code 2008-11-12 00:54:54 -08:00
net_namespace.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2008-10-31 00:17:34 -07:00
net-sysfs.c net: struct device - replace bus_id with dev_name(), dev_set_name() 2008-11-10 13:55:14 -08:00
net-sysfs.h netns: Fix device renaming for sysfs 2008-05-02 17:00:58 -07:00
netevent.c [NET]: net/core/netevent.c should #include <net/netevent.h> 2007-07-05 17:40:27 -07:00
netpoll.c net: convert print_mac to %pM 2008-10-27 17:06:18 -07:00
pktgen.c pktgen: add full reset functionality 2008-11-10 16:48:03 -08:00
request_sock.c net: convert BUG_TRAP to generic WARN_ON 2008-07-25 21:43:18 -07:00
rtnetlink.c net: Remove CONFIG_KMOD from net/ (towards removing CONFIG_KMOD entirely) 2008-10-16 15:24:51 -07:00
scm.c net: Fix recursive descent in __scm_destroy(). 2008-11-06 15:45:32 -08:00
skb_dma_map.c net: Fix off-by-one in skb_dma_map 2008-10-12 21:07:34 -07:00
skbuff.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2008-11-11 15:43:02 -08:00
sock.c udp: RCU handling for Unicast packets. 2008-10-29 02:11:14 -07:00
stream.c net: Rationalise email address: Network Specific Parts 2008-10-13 19:01:08 -07:00
sysctl_net_core.c net: '&' redux 2008-11-03 18:21:05 -08:00
user_dma.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2008-07-26 20:17:56 -07:00
utils.c printk ratelimiting rewrite 2008-07-25 10:53:29 -07:00