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[INET]: Remove per bucket rwlock in tcp/dccp ehash table.

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As done two years ago on IP route cache table (commit
22c047ccbc) , we can avoid using one
lock per hash bucket for the huge TCP/DCCP hash tables.

On a typical x86_64 platform, this saves about 2MB or 4MB of ram, for
litle performance differences. (we hit a different cache line for the
rwlock, but then the bucket cache line have a better sharing factor
among cpus, since we dirty it less often). For netstat or ss commands
that want a full scan of hash table, we perform fewer memory accesses.

Using a 'small' table of hashed rwlocks should be more than enough to
provide correct SMP concurrency between different buckets, without
using too much memory. Sizing of this table depends on
num_possible_cpus() and various CONFIG settings.

This patch provides some locking abstraction that may ease a future
work using a different model for TCP/DCCP table.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2007-11-07 02:40:20 -08:00
committed by David S. Miller
parent efac52762b
commit 230140cffa
8 changed files with 106 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
net/ipv6/inet6_hashtables.c
View File

@@ -37,9 +37,8 @@ void __inet6_hash(struct inet_hashinfo *hashinfo,
} else {
unsigned int hash;
sk->sk_hash = hash = inet6_sk_ehashfn(sk);
hash &= (hashinfo->ehash_size - 1);
list = &hashinfo->ehash[hash].chain;
lock = &hashinfo->ehash[hash].lock;
list = &inet_ehash_bucket(hashinfo, hash)->chain;
lock = inet_ehash_lockp(hashinfo, hash);
write_lock(lock);
}
@@ -70,9 +69,10 @@ struct sock *__inet6_lookup_established(struct inet_hashinfo *hashinfo,
*/
unsigned int hash = inet6_ehashfn(daddr, hnum, saddr, sport);
struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
rwlock_t *lock = inet_ehash_lockp(hashinfo, hash);
prefetch(head->chain.first);
read_lock(&head->lock);
read_lock(lock);
sk_for_each(sk, node, &head->chain) {
/* For IPV6 do the cheaper port and family tests first. */
if (INET6_MATCH(sk, hash, saddr, daddr, ports, dif))
@@ -92,12 +92,12 @@ struct sock *__inet6_lookup_established(struct inet_hashinfo *hashinfo,
goto hit;
}
}
read_unlock(&head->lock);
read_unlock(lock);
return NULL;
hit:
sock_hold(sk);
read_unlock(&head->lock);
read_unlock(lock);
return sk;
}
EXPORT_SYMBOL(__inet6_lookup_established);
@@ -175,12 +175,13 @@ static int __inet6_check_established(struct inet_timewait_death_row *death_row,
const unsigned int hash = inet6_ehashfn(daddr, lport, saddr,
inet->dport);
struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
rwlock_t *lock = inet_ehash_lockp(hinfo, hash);
struct sock *sk2;
const struct hlist_node *node;
struct inet_timewait_sock *tw;
prefetch(head->chain.first);
write_lock(&head->lock);
write_lock(lock);
/* Check TIME-WAIT sockets first. */
sk_for_each(sk2, node, &head->twchain) {
@@ -216,7 +217,7 @@ unique:
__sk_add_node(sk, &head->chain);
sk->sk_hash = hash;
sock_prot_inc_use(sk->sk_prot);
write_unlock(&head->lock);
write_unlock(lock);
if (twp != NULL) {
*twp = tw;
@@ -231,7 +232,7 @@ unique:
return 0;
not_unique:
write_unlock(&head->lock);
write_unlock(lock);
return -EADDRNOTAVAIL;
}