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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

9
net/ipv4/inet_diag.c
View File

@@ -747,13 +747,14 @@ skip_listen_ht:
for (i = s_i; i < hashinfo->ehash_size; i++) {
struct inet_ehash_bucket *head = &hashinfo->ehash[i];
rwlock_t *lock = inet_ehash_lockp(hashinfo, i);
struct sock *sk;
struct hlist_node *node;
if (i > s_i)
s_num = 0;
read_lock_bh(&head->lock);
read_lock_bh(lock);
num = 0;
sk_for_each(sk, node, &head->chain) {
struct inet_sock *inet = inet_sk(sk);
@@ -769,7 +770,7 @@ skip_listen_ht:
r->id.idiag_dport)
goto next_normal;
if (inet_csk_diag_dump(sk, skb, cb) < 0) {
read_unlock_bh(&head->lock);
read_unlock_bh(lock);
goto done;
}
next_normal:
@@ -791,14 +792,14 @@ next_normal:
r->id.idiag_dport)
goto next_dying;
if (inet_twsk_diag_dump(tw, skb, cb) < 0) {
read_unlock_bh(&head->lock);
read_unlock_bh(lock);
goto done;
}
next_dying:
++num;
}
}
read_unlock_bh(&head->lock);
read_unlock_bh(lock);
}
done: