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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 /include/net/inet6_hashtables.h
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 'include/net/inet6_hashtables.h')
-rw-r--r--include/net/inet6_hashtables.h21
1 files changed, 10 insertions, 11 deletions
diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
index 03df3b157960..5a2beed5a770 100644
--- a/include/net/inet6_hashtables.h
+++ b/include/net/inet6_hashtables.h
@@ -26,19 +26,18 @@
26struct inet_hashinfo; 26struct inet_hashinfo;
27 27
28/* I have no idea if this is a good hash for v6 or not. -DaveM */ 28/* I have no idea if this is a good hash for v6 or not. -DaveM */
29static inline int inet6_ehashfn(const struct in6_addr *laddr, const u16 lport, 29static inline unsigned int inet6_ehashfn(const struct in6_addr *laddr, const u16 lport,
30 const struct in6_addr *faddr, const u16 fport, 30 const struct in6_addr *faddr, const u16 fport)
31 const int ehash_size)
32{ 31{
33 int hashent = (lport ^ fport); 32 unsigned int hashent = (lport ^ fport);
34 33
35 hashent ^= (laddr->s6_addr32[3] ^ faddr->s6_addr32[3]); 34 hashent ^= (laddr->s6_addr32[3] ^ faddr->s6_addr32[3]);
36 hashent ^= hashent >> 16; 35 hashent ^= hashent >> 16;
37 hashent ^= hashent >> 8; 36 hashent ^= hashent >> 8;
38 return (hashent & (ehash_size - 1)); 37 return hashent;
39} 38}
40 39
41static inline int inet6_sk_ehashfn(const struct sock *sk, const int ehash_size) 40static inline int inet6_sk_ehashfn(const struct sock *sk)
42{ 41{
43 const struct inet_sock *inet = inet_sk(sk); 42 const struct inet_sock *inet = inet_sk(sk);
44 const struct ipv6_pinfo *np = inet6_sk(sk); 43 const struct ipv6_pinfo *np = inet6_sk(sk);
@@ -46,7 +45,7 @@ static inline int inet6_sk_ehashfn(const struct sock *sk, const int ehash_size)
46 const struct in6_addr *faddr = &np->daddr; 45 const struct in6_addr *faddr = &np->daddr;
47 const __u16 lport = inet->num; 46 const __u16 lport = inet->num;
48 const __u16 fport = inet->dport; 47 const __u16 fport = inet->dport;
49 return inet6_ehashfn(laddr, lport, faddr, fport, ehash_size); 48 return inet6_ehashfn(laddr, lport, faddr, fport);
50} 49}
51 50
52/* 51/*
@@ -69,14 +68,14 @@ static inline struct sock *
69 /* Optimize here for direct hit, only listening connections can 68 /* Optimize here for direct hit, only listening connections can
70 * have wildcards anyways. 69 * have wildcards anyways.
71 */ 70 */
72 const int hash = inet6_ehashfn(daddr, hnum, saddr, sport, 71 unsigned int hash = inet6_ehashfn(daddr, hnum, saddr, sport);
73 hashinfo->ehash_size); 72 struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
74 struct inet_ehash_bucket *head = &hashinfo->ehash[hash];
75 73
74 prefetch(head->chain.first);
76 read_lock(&head->lock); 75 read_lock(&head->lock);
77 sk_for_each(sk, node, &head->chain) { 76 sk_for_each(sk, node, &head->chain) {
78 /* For IPV6 do the cheaper port and family tests first. */ 77 /* For IPV6 do the cheaper port and family tests first. */
79 if (INET6_MATCH(sk, saddr, daddr, ports, dif)) 78 if (INET6_MATCH(sk, hash, saddr, daddr, ports, dif))
80 goto hit; /* You sunk my battleship! */ 79 goto hit; /* You sunk my battleship! */
81 } 80 }
82 /* Must check for a TIME_WAIT'er before going to listener hash. */ 81 /* Must check for a TIME_WAIT'er before going to listener hash. */