From 81c3d5470ecc70564eb9209946730fe2be93ad06 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 3 Oct 2005 14:13:38 -0700 Subject: [INET]: speedup inet (tcp/dccp) lookups Arnaldo and I agreed it could be applied now, because I have other pending patches depending on this one (Thank you Arnaldo) (The other important patch moves skc_refcnt in a separate cache line, so that the SMP/NUMA performance doesnt suffer from cache line ping pongs) 1) First some performance data : -------------------------------- tcp_v4_rcv() wastes a *lot* of time in __inet_lookup_established() The most time critical code is : sk_for_each(sk, node, &head->chain) { if (INET_MATCH(sk, acookie, saddr, daddr, ports, dif)) goto hit; /* You sunk my battleship! */ } The sk_for_each() does use prefetch() hints but only the begining of "struct sock" is prefetched. As INET_MATCH first comparison uses inet_sk(__sk)->daddr, wich is far away from the begining of "struct sock", it has to bring into CPU cache cold cache line. Each iteration has to use at least 2 cache lines. This can be problematic if some chains are very long. 2) The goal ----------- The idea I had is to change things so that INET_MATCH() may return FALSE in 99% of cases only using the data already in the CPU cache, using one cache line per iteration. 3) Description of the patch --------------------------- Adds a new 'unsigned int skc_hash' field in 'struct sock_common', filling a 32 bits hole on 64 bits platform. struct sock_common { unsigned short skc_family; volatile unsigned char skc_state; unsigned char skc_reuse; int skc_bound_dev_if; struct hlist_node skc_node; struct hlist_node skc_bind_node; atomic_t skc_refcnt; + unsigned int skc_hash; struct proto *skc_prot; }; Store in this 32 bits field the full hash, not masked by (ehash_size - 1) Using this full hash as the first comparison done in INET_MATCH permits us immediatly skip the element without touching a second cache line in case of a miss. Suppress the sk_hashent/tw_hashent fields since skc_hash (aliased to sk_hash and tw_hash) already contains the slot number if we mask with (ehash_size - 1) File include/net/inet_hashtables.h 64 bits platforms : #define INET_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)\ (((__sk)->sk_hash == (__hash)) ((*((__u64 *)&(inet_sk(__sk)->daddr)))== (__cookie)) && \ ((*((__u32 *)&(inet_sk(__sk)->dport))) == (__ports)) && \ (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif)))) 32bits platforms: #define TCP_IPV4_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)\ (((__sk)->sk_hash == (__hash)) && \ (inet_sk(__sk)->daddr == (__saddr)) && \ (inet_sk(__sk)->rcv_saddr == (__daddr)) && \ (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif)))) - Adds a prefetch(head->chain.first) in __inet_lookup_established()/__tcp_v4_check_established() and __inet6_lookup_established()/__tcp_v6_check_established() and __dccp_v4_check_established() to bring into cache the first element of the list, before the {read|write}_lock(&head->lock); Signed-off-by: Eric Dumazet Acked-by: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller --- net/ipv6/tcp_ipv6.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'net/ipv6/tcp_ipv6.c') diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 80643e6b346..d693cb988b7 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -209,9 +209,11 @@ static __inline__ void __tcp_v6_hash(struct sock *sk) lock = &tcp_hashinfo.lhash_lock; inet_listen_wlock(&tcp_hashinfo); } else { - sk->sk_hashent = inet6_sk_ehashfn(sk, tcp_hashinfo.ehash_size); - list = &tcp_hashinfo.ehash[sk->sk_hashent].chain; - lock = &tcp_hashinfo.ehash[sk->sk_hashent].lock; + unsigned int hash; + sk->sk_hash = hash = inet6_sk_ehashfn(sk); + hash &= (tcp_hashinfo.ehash_size - 1); + list = &tcp_hashinfo.ehash[hash].chain; + lock = &tcp_hashinfo.ehash[hash].lock; write_lock(lock); } @@ -322,13 +324,13 @@ static int __tcp_v6_check_established(struct sock *sk, const __u16 lport, const struct in6_addr *saddr = &np->daddr; const int dif = sk->sk_bound_dev_if; const u32 ports = INET_COMBINED_PORTS(inet->dport, lport); - const int hash = inet6_ehashfn(daddr, inet->num, saddr, inet->dport, - tcp_hashinfo.ehash_size); - struct inet_ehash_bucket *head = &tcp_hashinfo.ehash[hash]; + unsigned int hash = inet6_ehashfn(daddr, inet->num, saddr, inet->dport); + struct inet_ehash_bucket *head = inet_ehash_bucket(&tcp_hashinfo, hash); struct sock *sk2; const struct hlist_node *node; struct inet_timewait_sock *tw; + prefetch(head->chain.first); write_lock(&head->lock); /* Check TIME-WAIT sockets first. */ @@ -365,14 +367,14 @@ static int __tcp_v6_check_established(struct sock *sk, const __u16 lport, /* And established part... */ sk_for_each(sk2, node, &head->chain) { - if (INET6_MATCH(sk2, saddr, daddr, ports, dif)) + if (INET6_MATCH(sk2, hash, saddr, daddr, ports, dif)) goto not_unique; } unique: BUG_TRAP(sk_unhashed(sk)); __sk_add_node(sk, &head->chain); - sk->sk_hashent = hash; + sk->sk_hash = hash; sock_prot_inc_use(sk->sk_prot); write_unlock(&head->lock); -- cgit v1.2.3