[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>

8 files changed, 106 insertions, 37 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 4427dcd1e53a..8461cda37490 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 @@ struct inet_hashinfo {
          * 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_hashinfo {
         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 @@ static inline struct inet_ehash_bucket *inet_ehash_bucket(
         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 @@ static inline void __inet_hash(struct inet_hashinfo *hashinfo,
                 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 @@ static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
                 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 @@ static inline struct sock *
          */
         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 @@ static inline struct sock *
         }
         sk = NULL;
 out:
-        read_unlock(&head->lock);
+        read_unlock(lock);
         return sk;
 hit:
         sock_hold(sk);
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index d84973928033..7a3bea9c28c1 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1072,11 +1072,13 @@ static int __init dccp_init(void)
         }
 
         for (i = 0; i < dccp_hashinfo.ehash_size; i++) {
-                rwlock_init(&dccp_hashinfo.ehash[i].lock);
                 INIT_HLIST_HEAD(&dccp_hashinfo.ehash[i].chain);
                 INIT_HLIST_HEAD(&dccp_hashinfo.ehash[i].twchain);
         }
 
+        if (inet_ehash_locks_alloc(&dccp_hashinfo))
+                        goto out_free_dccp_ehash;
+
         bhash_order = ehash_order;
 
         do {
@@ -1091,7 +1093,7 @@ static int __init dccp_init(void)
 
         if (!dccp_hashinfo.bhash) {
                 DCCP_CRIT("Failed to allocate DCCP bind hash table");
-                goto out_free_dccp_ehash;
+                goto out_free_dccp_locks;
         }
 
         for (i = 0; i < dccp_hashinfo.bhash_size; i++) {
@@ -1121,6 +1123,8 @@ out_free_dccp_mib:
 out_free_dccp_bhash:
         free_pages((unsigned long)dccp_hashinfo.bhash, bhash_order);
         dccp_hashinfo.bhash = NULL;
+out_free_dccp_locks:
+        inet_ehash_locks_free(&dccp_hashinfo);
 out_free_dccp_ehash:
         free_pages((unsigned long)dccp_hashinfo.ehash, ehash_order);
         dccp_hashinfo.ehash = NULL;
@@ -1139,6 +1143,7 @@ static void __exit dccp_fini(void)
         free_pages((unsigned long)dccp_hashinfo.ehash,
                    get_order(dccp_hashinfo.ehash_size *
                              sizeof(struct inet_ehash_bucket)));
+        inet_ehash_locks_free(&dccp_hashinfo);
         kmem_cache_destroy(dccp_hashinfo.bind_bucket_cachep);
         dccp_ackvec_exit();
         dccp_sysctl_exit();
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index dc429b6b0ba6..b0170732b5e9 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -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:
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 16eecc7046a3..67704da04fc4 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -204,12 +204,13 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row,
         const __portpair ports = INET_COMBINED_PORTS(inet->dport, lport);
         unsigned int hash = inet_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) {
@@ -239,7 +240,7 @@ unique:
         BUG_TRAP(sk_unhashed(sk));
         __sk_add_node(sk, &head->chain);
         sock_prot_inc_use(sk->sk_prot);
-        write_unlock(&head->lock);
+        write_unlock(lock);
 
         if (twp) {
                 *twp = tw;
@@ -255,7 +256,7 @@ unique:
         return 0;
 
 not_unique:
-        write_unlock(&head->lock);
+        write_unlock(lock);
         return -EADDRNOTAVAIL;
 }
 
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 4e189e28f306..a60b99e0ebdc 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -20,16 +20,16 @@ static void __inet_twsk_kill(struct inet_timewait_sock *tw,
         struct inet_bind_hashbucket *bhead;
         struct inet_bind_bucket *tb;
         /* Unlink from established hashes. */
-        struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, tw->tw_hash);
+        rwlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
 
-        write_lock(&ehead->lock);
+        write_lock(lock);
         if (hlist_unhashed(&tw->tw_node)) {
-                write_unlock(&ehead->lock);
+                write_unlock(lock);
                 return;
         }
         __hlist_del(&tw->tw_node);
         sk_node_init(&tw->tw_node);
-        write_unlock(&ehead->lock);
+        write_unlock(lock);
 
         /* Disassociate with bind bucket. */
         bhead = &hashinfo->bhash[inet_bhashfn(tw->tw_num, hashinfo->bhash_size)];
@@ -59,6 +59,7 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
         const struct inet_sock *inet = inet_sk(sk);
         const struct inet_connection_sock *icsk = inet_csk(sk);
         struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
+        rwlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
         struct inet_bind_hashbucket *bhead;
         /* Step 1: Put TW into bind hash. Original socket stays there too.
            Note, that any socket with inet->num != 0 MUST be bound in
@@ -71,7 +72,7 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
         spin_unlock(&bhead->lock);
 
-        write_lock(&ehead->lock);
+        write_lock(lock);
 
         /* Step 2: Remove SK from established hash. */
         if (__sk_del_node_init(sk))
@@ -81,7 +82,7 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
         inet_twsk_add_node(tw, &ehead->twchain);
         atomic_inc(&tw->tw_refcnt);
 
-        write_unlock(&ehead->lock);
+        write_unlock(lock);
 }
 
 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c64072bb504b..8e65182f7af1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2456,11 +2456,11 @@ void __init tcp_init(void)
                                         thash_entries ? 0 : 512 * 1024);
         tcp_hashinfo.ehash_size = 1 << tcp_hashinfo.ehash_size;
         for (i = 0; i < tcp_hashinfo.ehash_size; i++) {
-                rwlock_init(&tcp_hashinfo.ehash[i].lock);
                 INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].chain);
                 INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].twchain);
         }
-
+        if (inet_ehash_locks_alloc(&tcp_hashinfo))
+                panic("TCP: failed to alloc ehash_locks");
         tcp_hashinfo.bhash =
                 alloc_large_system_hash("TCP bind",
                                         sizeof(struct inet_bind_hashbucket),
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index e9127cdced20..e566f3c67677 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2049,8 +2049,9 @@ static void *established_get_first(struct seq_file *seq)
                 struct sock *sk;
                 struct hlist_node *node;
                 struct inet_timewait_sock *tw;
+                rwlock_t *lock = inet_ehash_lockp(&tcp_hashinfo, st->bucket);
 
-                read_lock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
+                read_lock_bh(lock);
                 sk_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
                         if (sk->sk_family != st->family) {
                                 continue;
@@ -2067,7 +2068,7 @@ static void *established_get_first(struct seq_file *seq)
                         rc = tw;
                         goto out;
                 }
-                read_unlock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
+                read_unlock_bh(lock);
                 st->state = TCP_SEQ_STATE_ESTABLISHED;
         }
 out:
@@ -2094,11 +2095,11 @@ get_tw:
                         cur = tw;
                         goto out;
                 }
-                read_unlock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
+                read_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
                 st->state = TCP_SEQ_STATE_ESTABLISHED;
 
                 if (++st->bucket < tcp_hashinfo.ehash_size) {
-                        read_lock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
+                        read_lock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
                         sk = sk_head(&tcp_hashinfo.ehash[st->bucket].chain);
                 } else {
                         cur = NULL;
@@ -2206,7 +2207,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v)
         case TCP_SEQ_STATE_TIME_WAIT:
         case TCP_SEQ_STATE_ESTABLISHED:
                 if (v)
-                        read_unlock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
+                        read_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
                 break;
         }
 }
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index d6f1026f1943..adc73adadfae 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -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;
 }