[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/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 4427dcd..8461cda 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -37,7 +37,6 @@
* I'll experiment with dynamic table growth later.
*/
struct inet_ehash_bucket {
- rwlock_t lock;
struct hlist_head chain;
struct hlist_head twchain;
};
@@ -100,6 +99,9 @@
* TIME_WAIT sockets use a separate chain (twchain).
*/
struct inet_ehash_bucket *ehash;
+ rwlock_t *ehash_locks;
+ unsigned int ehash_size;
+ unsigned int ehash_locks_mask;
/* Ok, let's try this, I give up, we do need a local binding
* TCP hash as well as the others for fast bind/connect.
@@ -107,7 +109,7 @@
struct inet_bind_hashbucket *bhash;
unsigned int bhash_size;
- unsigned int ehash_size;
+ /* Note : 4 bytes padding on 64 bit arches */
/* All sockets in TCP_LISTEN state will be in here. This is the only
* table where wildcard'd TCP sockets can exist. Hash function here
@@ -134,6 +136,62 @@
return &hashinfo->ehash[hash & (hashinfo->ehash_size - 1)];
}
+static inline rwlock_t *inet_ehash_lockp(
+ struct inet_hashinfo *hashinfo,
+ unsigned int hash)
+{
+ return &hashinfo->ehash_locks[hash & hashinfo->ehash_locks_mask];
+}
+
+static inline int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
+{
+ unsigned int i, size = 256;
+#if defined(CONFIG_PROVE_LOCKING)
+ unsigned int nr_pcpus = 2;
+#else
+ unsigned int nr_pcpus = num_possible_cpus();
+#endif
+ if (nr_pcpus >= 4)
+ size = 512;
+ if (nr_pcpus >= 8)
+ size = 1024;
+ if (nr_pcpus >= 16)
+ size = 2048;
+ if (nr_pcpus >= 32)
+ size = 4096;
+ if (sizeof(rwlock_t) != 0) {
+#ifdef CONFIG_NUMA
+ if (size * sizeof(rwlock_t) > PAGE_SIZE)
+ hashinfo->ehash_locks = vmalloc(size * sizeof(rwlock_t));
+ else
+#endif
+ hashinfo->ehash_locks = kmalloc(size * sizeof(rwlock_t),
+ GFP_KERNEL);
+ if (!hashinfo->ehash_locks)
+ return ENOMEM;
+ for (i = 0; i < size; i++)
+ rwlock_init(&hashinfo->ehash_locks[i]);
+ }
+ hashinfo->ehash_locks_mask = size - 1;
+ return 0;
+}
+
+static inline void inet_ehash_locks_free(struct inet_hashinfo *hashinfo)
+{
+ if (hashinfo->ehash_locks) {
+#ifdef CONFIG_NUMA
+ unsigned int size = (hashinfo->ehash_locks_mask + 1) *
+ sizeof(rwlock_t);
+ if (size > PAGE_SIZE)
+ vfree(hashinfo->ehash_locks);
+ else
+#else
+ kfree(hashinfo->ehash_locks);
+#endif
+ hashinfo->ehash_locks = NULL;
+ }
+}
+
extern struct inet_bind_bucket *
inet_bind_bucket_create(struct kmem_cache *cachep,
struct inet_bind_hashbucket *head,
@@ -222,7 +280,7 @@
sk->sk_hash = inet_sk_ehashfn(sk);
head = inet_ehash_bucket(hashinfo, sk->sk_hash);
list = &head->chain;
- lock = &head->lock;
+ lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
write_lock(lock);
}
__sk_add_node(sk, list);
@@ -253,7 +311,7 @@
inet_listen_wlock(hashinfo);
lock = &hashinfo->lhash_lock;
} else {
- lock = &inet_ehash_bucket(hashinfo, sk->sk_hash)->lock;
+ lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
write_lock_bh(lock);
}
@@ -354,9 +412,10 @@
*/
unsigned int hash = inet_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) {
if (INET_MATCH(sk, hash, acookie, saddr, daddr, ports, dif))
goto hit; /* You sunk my battleship! */
@@ -369,7 +428,7 @@
}
sk = NULL;
out:
- read_unlock(&head->lock);
+ read_unlock(lock);
return sk;
hit:
sock_hold(sk);