[INET]: Remove per bucket rwlock in tcp/dccp ehash table.
As done two years ago on IP route cache table (commit
22c047ccbc68fa8f3fa57f0e8f906479a062c426) , 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>
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index dc429b6..b017073 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -747,13 +747,14 @@
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 @@
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 @@
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: