From 2b77bdde97ae8241dcc23110a4e837acfbc83438 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 8 Jun 2011 23:31:27 -0700 Subject: [PATCH] inetpeer: lower false sharing effect Profiles show false sharing in addr_compare() because refcnt/dtime changes dirty the first inet_peer cache line, where are lying the keys used at lookup time. If many cpus are calling inet_getpeer() and inet_putpeer(), or need frag ids, addr_compare() is in 2nd position in "perf top". Before patch, my udpflood bench (16 threads) on my 2x4x2 machine : 5784.00 9.7% csum_partial_copy_generic [kernel] 3356.00 5.6% addr_compare [kernel] 2638.00 4.4% fib_table_lookup [kernel] 2625.00 4.4% ip_fragment [kernel] 1934.00 3.2% neigh_lookup [kernel] 1617.00 2.7% udp_sendmsg [kernel] 1608.00 2.7% __ip_route_output_key [kernel] 1480.00 2.5% __ip_append_data [kernel] 1396.00 2.3% kfree [kernel] 1195.00 2.0% kmem_cache_free [kernel] 1157.00 1.9% inet_getpeer [kernel] 1121.00 1.9% neigh_resolve_output [kernel] 1012.00 1.7% dev_queue_xmit [kernel] # time ./udpflood.sh real 0m44.511s user 0m20.020s sys 11m22.780s # time ./udpflood.sh real 0m44.099s user 0m20.140s sys 11m15.870s After patch, no more addr_compare() in profiles : 4171.00 10.7% csum_partial_copy_generic [kernel] 1787.00 4.6% fib_table_lookup [kernel] 1756.00 4.5% ip_fragment [kernel] 1234.00 3.2% udp_sendmsg [kernel] 1191.00 3.0% neigh_lookup [kernel] 1118.00 2.9% __ip_append_data [kernel] 1022.00 2.6% kfree [kernel] 993.00 2.5% __ip_route_output_key [kernel] 841.00 2.2% neigh_resolve_output [kernel] 816.00 2.1% kmem_cache_free [kernel] 658.00 1.7% ia32_sysenter_target [kernel] 632.00 1.6% kmem_cache_alloc_node [kernel] # time ./udpflood.sh real 0m41.587s user 0m19.190s sys 10m36.370s # time ./udpflood.sh real 0m41.486s user 0m19.290s sys 10m33.650s Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/inetpeer.h | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h index 1f0966f91760..39d123081e7e 100644 --- a/include/net/inetpeer.h +++ b/include/net/inetpeer.h @@ -32,12 +32,17 @@ struct inet_peer { struct inet_peer __rcu *avl_left, *avl_right; struct inetpeer_addr daddr; __u32 avl_height; - __u32 dtime; /* the time of last use of not - * referenced entries */ - atomic_t refcnt; + + u32 metrics[RTAX_MAX]; + u32 rate_tokens; /* rate limiting for ICMP */ + unsigned long rate_last; + unsigned long pmtu_expires; + u32 pmtu_orig; + u32 pmtu_learned; + struct inetpeer_addr_base redirect_learned; /* * Once inet_peer is queued for deletion (refcnt == -1), following fields - * are not available: rid, ip_id_count, tcp_ts, tcp_ts_stamp, metrics + * are not available: rid, ip_id_count, tcp_ts, tcp_ts_stamp * We can share memory with rcu_head to help keep inet_peer small. */ union { @@ -46,17 +51,14 @@ struct inet_peer { atomic_t ip_id_count; /* IP ID for the next packet */ __u32 tcp_ts; __u32 tcp_ts_stamp; - u32 metrics[RTAX_MAX]; - u32 rate_tokens; /* rate limiting for ICMP */ - unsigned long rate_last; - unsigned long pmtu_expires; - u32 pmtu_orig; - u32 pmtu_learned; - struct inetpeer_addr_base redirect_learned; }; struct rcu_head rcu; struct inet_peer *gc_next; }; + + /* following fields might be frequently dirtied */ + __u32 dtime; /* the time of last use of not referenced entries */ + atomic_t refcnt; }; void inet_initpeers(void) __init; -- 2.34.1