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2f970d8357
linux/net/ipv4
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Eric Dumazet 2f970d8357 [IPV4]: rt_cache_stat can be statically defined 
Using __get_cpu_var(obj) is slightly faster than per_cpu_ptr(obj, 
raw_smp_processor_id()).

1) Smaller code and memory use
For static and small objects, DEFINE_PER_CPU(type, object) is preferred over a 
alloc_percpu() : Better and smaller code to access them, and no extra memory 
(storing the pointer, and the percpu array of pointers)

x86_64 code before patch

mov    1237577(%rip),%rax        # ffffffff803e5990 <rt_cache_stat>
not    %rax  # part of per_cpu machinery
mov    %gs:0x3c,%edx # get cpu number
movslq %edx,%rdx # extend 32 bits cpu number to 64 bits
mov    (%rax,%rdx,8),%rax # get the pointer for this cpu
incl   0x38(%rax)

x86_64 code after patch

mov    $per_cpu__rt_cache_stat,%rdx
mov    %gs:0x48,%rax # get percpu data offset
incl   0x38(%rax,%rdx,1)

2) False sharing avoidance for SMP :
For a small NR_CPUS, the array of per cpu pointers allocated in alloc_percpu() 
can be <= 32 bytes. This let slab code gives a part of a cache line. If the 
other part of this 64 bytes (or 128 bytes) cache line is used by a mostly 
written object, we can have false sharing and expensive per_cpu_ptr() operations.

Size of rt_cache_stat is 64 bytes, so this patch is not a danger of a too big 
increase of bss (in UP mode) or static per_cpu data for SMP 
(PERCPU_ENOUGH_ROOM is currently 32768 bytes)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-17 02:54:36 -08:00
..
ipvs [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
netfilter [NETFILTER]: ip_conntrack_proto_gre.c needs linux/interrupt.h 2006-01-17 02:42:02 -08:00
af_inet.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
ah4.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
arp.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
datagram.c [NET]: Fix sparse warnings 2005-08-29 16:01:32 -07:00
devinet.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
esp4.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
fib_frontend.c x86: Work around compiler code generation bug with -Os 2006-01-14 22:08:28 -08:00
fib_hash.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
fib_lookup.h [IPV4]: Prepare FIB core for RCU. 2005-08-29 16:08:31 -07:00
fib_rules.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
fib_semantics.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
fib_trie.c [IPV4] fib_trie: build fix 2006-01-03 14:38:34 -08:00
icmp.c [NET]: Change some "if (x) BUG();" to "BUG_ON(x);" 2006-01-09 14:16:18 -08:00
igmp.c [NET]: Remove more unneeded typecasts on *malloc() 2006-01-11 16:32:14 -08:00
inet_connection_sock.c [ICSK]: Move v4_addr2sockaddr from TCP to icsk 2006-01-03 13:10:39 -08:00
inet_diag.c [INET_DIAG]: Introduce sk_diag_fill 2006-01-09 14:56:56 -08:00
inet_hashtables.c [INET]: Generalise tcp_v4_hash_connect 2006-01-03 13:10:55 -08:00
inet_timewait_sock.c [TWSK]: Introduce struct timewait_sock_ops 2006-01-03 13:10:54 -08:00
inetpeer.c [NET]: Change some "if (x) BUG();" to "BUG_ON(x);" 2006-01-09 14:16:18 -08:00
ip_forward.c [IPV4]: Remove some dead code from ip_forward() 2005-08-29 16:03:06 -07:00
ip_fragment.c [NET]: Endian-annotate struct iphdr 2006-01-06 13:24:29 -08:00
ip_gre.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
ip_input.c [NETFILTER]: Keep conntrack reference until IPsec policy checks are done 2006-01-07 12:57:36 -08:00
ip_options.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
ip_output.c [IPV4]: ip_output.c needs xfrm.h 2006-01-09 14:16:28 -08:00
ip_sockglue.c [NET]: Remove more unneeded typecasts on *malloc() 2006-01-11 16:32:14 -08:00
ipcomp.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
ipconfig.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
ipip.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
ipmr.c [PATCH] capable/capability.h (net/) 2006-01-11 18:42:14 -08:00
Kconfig [TCP] BIC: CUBIC window growth (2.0) 2006-01-03 13:10:28 -08:00
Makefile [NETFILTER]: net/ipv[46]/netfilter.c cleanups 2006-01-10 12:54:29 -08:00
multipath_drr.c [IPV4]: possible cleanups 2005-08-29 15:33:20 -07:00
multipath_random.c [IPV4]: Multipath modules need a license to prevent kernel tainting. 2005-06-13 14:29:06 -07:00
multipath_rr.c [IPV4]: Multipath modules need a license to prevent kernel tainting. 2005-06-13 14:29:06 -07:00
multipath_wrandom.c [NET]: kfree cleanup 2005-11-08 09:41:34 -08:00
multipath.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
netfilter.c [NETFILTER]: net/ipv[46]/netfilter.c cleanups 2006-01-10 12:54:29 -08:00
proc.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
protocol.c [TCP]: Move the tcp sock states to net/tcp_states.h 2005-08-29 15:41:54 -07:00
raw.c [NETFILTER]: Keep conntrack reference until IPsec policy checks are done 2006-01-07 12:57:36 -08:00
route.c [IPV4]: rt_cache_stat can be statically defined 2006-01-17 02:54:36 -08:00
syncookies.c [ICSK]: Rename struct tcp_func to struct inet_connection_sock_af_ops 2006-01-03 13:10:38 -08:00
sysctl_net_ipv4.c [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
tcp_bic.c [TCP] BIC: spelling and whitespace 2006-01-03 13:10:27 -08:00
tcp_cong.c [TCP]: less inline's 2006-01-03 16:03:49 -08:00
tcp_cubic.c [TCP] cubic: use Newton-Raphson 2006-01-03 13:11:09 -08:00
tcp_diag.c [INET_DIAG]: Move the tcp_diag interface to the proper place 2005-08-29 15:57:54 -07:00
tcp_highspeed.c [TCP]: TCP highspeed build error 2005-11-17 14:11:18 -08:00
tcp_htcp.c [TCP]: add tcp_slow_start helper 2005-11-10 17:07:24 -08:00
tcp_hybla.c [TCP]: fix congestion window update when using TSO deferal 2005-11-10 16:53:30 -08:00
tcp_input.c [NET]: Change some "if (x) BUG();" to "BUG_ON(x);" 2006-01-09 14:16:18 -08:00
tcp_ipv4.c [NETFILTER]: Keep conntrack reference until IPsec policy checks are done 2006-01-07 12:57:36 -08:00
tcp_minisocks.c [IPV6]: Introduce inet6_timewait_sock 2006-01-03 13:10:47 -08:00
tcp_output.c [TCP]: less inline's 2006-01-03 16:03:49 -08:00
tcp_scalable.c [TCP]: add tcp_slow_start helper 2005-11-10 17:07:24 -08:00
tcp_timer.c [TCP]: spelling fixes 2005-11-10 17:13:47 -08:00
tcp_vegas.c [TCP] tcp_vegas: Fix slow start 2006-01-04 13:59:32 -08:00
tcp_westwood.c [INET_DIAG]: Rename tcp_diag.[ch] to inet_diag.[ch] 2005-08-29 15:57:48 -07:00
tcp.c [IP_SOCKGLUE]: Remove most of the tcp specific calls 2006-01-03 13:10:58 -08:00
udp.c [NETFILTER]: Keep conntrack reference until IPsec policy checks are done 2006-01-07 12:57:36 -08:00
xfrm4_input.c [IPV4/6]: Netfilter IPsec input hooks 2006-01-07 12:57:31 -08:00
xfrm4_output.c [NETFILTER]: Redo policy lookups after NAT when neccessary 2006-01-07 12:57:35 -08:00
xfrm4_policy.c [XFRM]: Handle DCCP in xfrm{4,6}_decode_session 2005-12-19 14:03:46 -08:00
xfrm4_state.c [XFRM]: IPsec tunnel wildcard address support 2006-01-13 14:34:36 -08:00
xfrm4_tunnel.c [NET]: Make ipip/ip6_tunnel independant of XFRM 2005-07-19 14:03:34 -07:00