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authorEric Dumazet <dada1@cosmosbay.com>2005-10-03 17:13:38 -0400
committerDavid S. Miller <davem@davemloft.net>2005-10-03 17:13:38 -0400
commit81c3d5470ecc70564eb9209946730fe2be93ad06 (patch)
tree1efa553c305a6453769dacfaf580bc6ccf146d82 /net/ipv6
parent399de50bbbb2501a6db43daaa8a2dafbc9bcfe0c (diff)
[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 <dada1@cosmosbay.com> Acked-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/tcp_ipv6.c18
1 files changed, 10 insertions, 8 deletions
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 80643e6b346b..d693cb988b78 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)
209 lock = &tcp_hashinfo.lhash_lock; 209 lock = &tcp_hashinfo.lhash_lock;
210 inet_listen_wlock(&tcp_hashinfo); 210 inet_listen_wlock(&tcp_hashinfo);
211 } else { 211 } else {
212 sk->sk_hashent = inet6_sk_ehashfn(sk, tcp_hashinfo.ehash_size); 212 unsigned int hash;
213 list = &tcp_hashinfo.ehash[sk->sk_hashent].chain; 213 sk->sk_hash = hash = inet6_sk_ehashfn(sk);
214 lock = &tcp_hashinfo.ehash[sk->sk_hashent].lock; 214 hash &= (tcp_hashinfo.ehash_size - 1);
215 list = &tcp_hashinfo.ehash[hash].chain;
216 lock = &tcp_hashinfo.ehash[hash].lock;
215 write_lock(lock); 217 write_lock(lock);
216 } 218 }
217 219
@@ -322,13 +324,13 @@ static int __tcp_v6_check_established(struct sock *sk, const __u16 lport,
322 const struct in6_addr *saddr = &np->daddr; 324 const struct in6_addr *saddr = &np->daddr;
323 const int dif = sk->sk_bound_dev_if; 325 const int dif = sk->sk_bound_dev_if;
324 const u32 ports = INET_COMBINED_PORTS(inet->dport, lport); 326 const u32 ports = INET_COMBINED_PORTS(inet->dport, lport);
325 const int hash = inet6_ehashfn(daddr, inet->num, saddr, inet->dport, 327 unsigned int hash = inet6_ehashfn(daddr, inet->num, saddr, inet->dport);
326 tcp_hashinfo.ehash_size); 328 struct inet_ehash_bucket *head = inet_ehash_bucket(&tcp_hashinfo, hash);
327 struct inet_ehash_bucket *head = &tcp_hashinfo.ehash[hash];
328 struct sock *sk2; 329 struct sock *sk2;
329 const struct hlist_node *node; 330 const struct hlist_node *node;
330 struct inet_timewait_sock *tw; 331 struct inet_timewait_sock *tw;
331 332
333 prefetch(head->chain.first);
332 write_lock(&head->lock); 334 write_lock(&head->lock);
333 335
334 /* Check TIME-WAIT sockets first. */ 336 /* Check TIME-WAIT sockets first. */
@@ -365,14 +367,14 @@ static int __tcp_v6_check_established(struct sock *sk, const __u16 lport,
365 367
366 /* And established part... */ 368 /* And established part... */
367 sk_for_each(sk2, node, &head->chain) { 369 sk_for_each(sk2, node, &head->chain) {
368 if (INET6_MATCH(sk2, saddr, daddr, ports, dif)) 370 if (INET6_MATCH(sk2, hash, saddr, daddr, ports, dif))
369 goto not_unique; 371 goto not_unique;
370 } 372 }
371 373
372unique: 374unique:
373 BUG_TRAP(sk_unhashed(sk)); 375 BUG_TRAP(sk_unhashed(sk));
374 __sk_add_node(sk, &head->chain); 376 __sk_add_node(sk, &head->chain);
375 sk->sk_hashent = hash; 377 sk->sk_hash = hash;
376 sock_prot_inc_use(sk->sk_prot); 378 sock_prot_inc_use(sk->sk_prot);
377 write_unlock(&head->lock); 379 write_unlock(&head->lock);
378 380