Skip to content

Commit

Permalink
net: listening_hash get a spinlock per bucket
Browse files Browse the repository at this point in the history 
This patch prepares RCU migration of listening_hash table for
TCP/DCCP protocols.

listening_hash table being small (32 slots per protocol), we add
a spinlock for each slot, instead of a single rwlock for whole table.

This should reduce hold time of readers, and writers concurrency.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
  • Loading branch information
Eric Dumazet authored and David S. Miller committed Nov 20, 2008
1 parent d8b83c5 commit 5caea4e
Show file tree
Hide file tree
Showing 6 changed files with 79 additions and 119 deletions.
45 changes: 15 additions & 30 deletions include/net/inet_hashtables.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,11 @@ struct inet_bind_hashbucket {
struct hlist_head chain;
};

struct inet_listen_hashbucket {
spinlock_t lock;
struct hlist_head head;
};

/* This is for listening sockets, thus all sockets which possess wildcards. */
#define INET_LHTABLE_SIZE 32 /* Yes, really, this is all you need. */

Expand All @@ -123,22 +128,21 @@ struct inet_hashinfo {
unsigned int bhash_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
* is just local port number.
*/
struct hlist_head listening_hash[INET_LHTABLE_SIZE];
struct kmem_cache *bind_bucket_cachep;

/* All the above members are written once at bootup and
* never written again _or_ are predominantly read-access.
*
* Now align to a new cache line as all the following members
* are often dirty.
* might be often dirty.
*/
/* 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
* is just local port number.
*/
rwlock_t lhash_lock ____cacheline_aligned;
atomic_t lhash_users;
wait_queue_head_t lhash_wait;
struct kmem_cache *bind_bucket_cachep;
struct inet_listen_hashbucket listening_hash[INET_LHTABLE_SIZE]
____cacheline_aligned_in_smp;

};

static inline struct inet_ehash_bucket *inet_ehash_bucket(
Expand Down Expand Up @@ -236,26 +240,7 @@ extern void __inet_inherit_port(struct sock *sk, struct sock *child);

extern void inet_put_port(struct sock *sk);

extern void inet_listen_wlock(struct inet_hashinfo *hashinfo);

/*
* - We may sleep inside this lock.
* - If sleeping is not required (or called from BH),
* use plain read_(un)lock(&inet_hashinfo.lhash_lock).
*/
static inline void inet_listen_lock(struct inet_hashinfo *hashinfo)
{
/* read_lock synchronizes to candidates to writers */
read_lock(&hashinfo->lhash_lock);
atomic_inc(&hashinfo->lhash_users);
read_unlock(&hashinfo->lhash_lock);
}

static inline void inet_listen_unlock(struct inet_hashinfo *hashinfo)
{
if (atomic_dec_and_test(&hashinfo->lhash_users))
wake_up(&hashinfo->lhash_wait);
}
void inet_hashinfo_init(struct inet_hashinfo *h);

extern void __inet_hash_nolisten(struct sock *sk);
extern void inet_hash(struct sock *sk);
Expand Down
8 changes: 2 additions & 6 deletions net/dccp/proto.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -44,12 +44,7 @@ atomic_t dccp_orphan_count = ATOMIC_INIT(0);

EXPORT_SYMBOL_GPL(dccp_orphan_count);

struct inet_hashinfo __cacheline_aligned dccp_hashinfo = {
.lhash_lock = RW_LOCK_UNLOCKED,
.lhash_users = ATOMIC_INIT(0),
.lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(dccp_hashinfo.lhash_wait),
};

struct inet_hashinfo dccp_hashinfo;
EXPORT_SYMBOL_GPL(dccp_hashinfo);

/* the maximum queue length for tx in packets. 0 is no limit */
Expand Down Expand Up @@ -1030,6 +1025,7 @@ static int __init dccp_init(void)
BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
FIELD_SIZEOF(struct sk_buff, cb));

inet_hashinfo_init(&dccp_hashinfo);
dccp_hashinfo.bind_bucket_cachep =
kmem_cache_create("dccp_bind_bucket",
sizeof(struct inet_bind_bucket), 0,
Expand Down
12 changes: 7 additions & 5 deletions net/ipv4/inet_diag.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -718,13 +718,15 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
if (!(r->idiag_states & (TCPF_LISTEN | TCPF_SYN_RECV)))
goto skip_listen_ht;

inet_listen_lock(hashinfo);
for (i = s_i; i < INET_LHTABLE_SIZE; i++) {
struct sock *sk;
struct hlist_node *node;
struct inet_listen_hashbucket *ilb;

num = 0;
sk_for_each(sk, node, &hashinfo->listening_hash[i]) {
ilb = &hashinfo->listening_hash[i];
spin_lock_bh(&ilb->lock);
sk_for_each(sk, node, &ilb->head) {
struct inet_sock *inet = inet_sk(sk);

if (num < s_num) {
Expand All @@ -742,7 +744,7 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
goto syn_recv;

if (inet_csk_diag_dump(sk, skb, cb) < 0) {
inet_listen_unlock(hashinfo);
spin_unlock_bh(&ilb->lock);
goto done;
}

Expand All @@ -751,7 +753,7 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
goto next_listen;

if (inet_diag_dump_reqs(skb, sk, cb) < 0) {
inet_listen_unlock(hashinfo);
spin_unlock_bh(&ilb->lock);
goto done;
}

Expand All @@ -760,12 +762,12 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
cb->args[4] = 0;
++num;
}
spin_unlock_bh(&ilb->lock);

s_num = 0;
cb->args[3] = 0;
cb->args[4] = 0;
}
inet_listen_unlock(hashinfo);
skip_listen_ht:
cb->args[0] = 1;
s_i = num = s_num = 0;
Expand Down
86 changes: 31 additions & 55 deletions net/ipv4/inet_hashtables.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -110,35 +110,6 @@ void __inet_inherit_port(struct sock *sk, struct sock *child)

EXPORT_SYMBOL_GPL(__inet_inherit_port);

/*
* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
* Look, when several writers sleep and reader wakes them up, all but one
* immediately hit write lock and grab all the cpus. Exclusive sleep solves
* this, _but_ remember, it adds useless work on UP machines (wake up each
* exclusive lock release). It should be ifdefed really.
*/
void inet_listen_wlock(struct inet_hashinfo *hashinfo)
__acquires(hashinfo->lhash_lock)
{
write_lock(&hashinfo->lhash_lock);

if (atomic_read(&hashinfo->lhash_users)) {
DEFINE_WAIT(wait);

for (;;) {
prepare_to_wait_exclusive(&hashinfo->lhash_wait,
&wait, TASK_UNINTERRUPTIBLE);
if (!atomic_read(&hashinfo->lhash_users))
break;
write_unlock_bh(&hashinfo->lhash_lock);
schedule();
write_lock_bh(&hashinfo->lhash_lock);
}

finish_wait(&hashinfo->lhash_wait, &wait);
}
}

/*
* Don't inline this cruft. Here are some nice properties to exploit here. The
* BSD API does not allow a listening sock to specify the remote port nor the
Expand Down Expand Up @@ -191,25 +162,25 @@ struct sock *__inet_lookup_listener(struct net *net,
const int dif)
{
struct sock *sk = NULL;
const struct hlist_head *head;
struct inet_listen_hashbucket *ilb;

read_lock(&hashinfo->lhash_lock);
head = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
if (!hlist_empty(head)) {
const struct inet_sock *inet = inet_sk((sk = __sk_head(head)));
ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
spin_lock(&ilb->lock);
if (!hlist_empty(&ilb->head)) {
const struct inet_sock *inet = inet_sk((sk = __sk_head(&ilb->head)));

if (inet->num == hnum && !sk->sk_node.next &&
(!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
(sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
!sk->sk_bound_dev_if && net_eq(sock_net(sk), net))
goto sherry_cache;
sk = inet_lookup_listener_slow(net, head, daddr, hnum, dif);
sk = inet_lookup_listener_slow(net, &ilb->head, daddr, hnum, dif);
}
if (sk) {
sherry_cache:
sock_hold(sk);
}
read_unlock(&hashinfo->lhash_lock);
spin_unlock(&ilb->lock);
return sk;
}
EXPORT_SYMBOL_GPL(__inet_lookup_listener);
Expand Down Expand Up @@ -389,23 +360,20 @@ EXPORT_SYMBOL_GPL(__inet_hash_nolisten);
static void __inet_hash(struct sock *sk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct hlist_head *list;
rwlock_t *lock;
struct inet_listen_hashbucket *ilb;

if (sk->sk_state != TCP_LISTEN) {
__inet_hash_nolisten(sk);
return;
}

WARN_ON(!sk_unhashed(sk));
list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
lock = &hashinfo->lhash_lock;
ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];

inet_listen_wlock(hashinfo);
__sk_add_node(sk, list);
spin_lock(&ilb->lock);
__sk_add_node(sk, &ilb->head);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
write_unlock(lock);
wake_up(&hashinfo->lhash_wait);
spin_unlock(&ilb->lock);
}

void inet_hash(struct sock *sk)
Expand All @@ -420,29 +388,27 @@ EXPORT_SYMBOL_GPL(inet_hash);

void inet_unhash(struct sock *sk)
{
rwlock_t *lock;
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

if (sk_unhashed(sk))
goto out;
return;

if (sk->sk_state == TCP_LISTEN) {
local_bh_disable();
inet_listen_wlock(hashinfo);
lock = &hashinfo->lhash_lock;
struct inet_listen_hashbucket *ilb;

ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
spin_lock_bh(&ilb->lock);
if (__sk_del_node_init(sk))
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
spin_unlock_bh(&ilb->lock);
} else {
lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
rwlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

write_lock_bh(lock);
if (__sk_nulls_del_node_init_rcu(sk))
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
write_unlock_bh(lock);
}

write_unlock_bh(lock);
out:
if (sk->sk_state == TCP_LISTEN)
wake_up(&hashinfo->lhash_wait);
}
EXPORT_SYMBOL_GPL(inet_unhash);

Expand Down Expand Up @@ -556,3 +522,13 @@ int inet_hash_connect(struct inet_timewait_death_row *death_row,
}

EXPORT_SYMBOL_GPL(inet_hash_connect);

void inet_hashinfo_init(struct inet_hashinfo *h)
{
int i;

for (i = 0; i < INET_LHTABLE_SIZE; i++)
spin_lock_init(&h->listening_hash[i].lock);
}

EXPORT_SYMBOL_GPL(inet_hashinfo_init);
24 changes: 12 additions & 12 deletions net/ipv4/tcp_ipv4.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -97,11 +97,7 @@ struct tcp_md5sig_key *tcp_v4_md5_do_lookup(struct sock *sk, __be32 addr)
}
#endif

struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
.lhash_lock = __RW_LOCK_UNLOCKED(tcp_hashinfo.lhash_lock),
.lhash_users = ATOMIC_INIT(0),
.lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
};
struct inet_hashinfo tcp_hashinfo;

static inline __u32 tcp_v4_init_sequence(struct sk_buff *skb)
{
Expand Down Expand Up @@ -1874,15 +1870,18 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
struct inet_connection_sock *icsk;
struct hlist_node *node;
struct sock *sk = cur;
struct inet_listen_hashbucket *ilb;
struct tcp_iter_state *st = seq->private;
struct net *net = seq_file_net(seq);

if (!sk) {
st->bucket = 0;
sk = sk_head(&tcp_hashinfo.listening_hash[0]);
ilb = &tcp_hashinfo.listening_hash[0];
spin_lock_bh(&ilb->lock);
sk = sk_head(&ilb->head);
goto get_sk;
}

ilb = &tcp_hashinfo.listening_hash[st->bucket];
++st->num;

if (st->state == TCP_SEQ_STATE_OPENREQ) {
Expand Down Expand Up @@ -1932,8 +1931,11 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
}
read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
}
spin_unlock_bh(&ilb->lock);
if (++st->bucket < INET_LHTABLE_SIZE) {
sk = sk_head(&tcp_hashinfo.listening_hash[st->bucket]);
ilb = &tcp_hashinfo.listening_hash[st->bucket];
spin_lock_bh(&ilb->lock);
sk = sk_head(&ilb->head);
goto get_sk;
}
cur = NULL;
Expand Down Expand Up @@ -2066,12 +2068,10 @@ static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
void *rc;
struct tcp_iter_state *st = seq->private;

inet_listen_lock(&tcp_hashinfo);
st->state = TCP_SEQ_STATE_LISTENING;
rc = listening_get_idx(seq, &pos);

if (!rc) {
inet_listen_unlock(&tcp_hashinfo);
st->state = TCP_SEQ_STATE_ESTABLISHED;
rc = established_get_idx(seq, pos);
}
Expand Down Expand Up @@ -2103,7 +2103,6 @@ static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
case TCP_SEQ_STATE_LISTENING:
rc = listening_get_next(seq, v);
if (!rc) {
inet_listen_unlock(&tcp_hashinfo);
st->state = TCP_SEQ_STATE_ESTABLISHED;
rc = established_get_first(seq);
}
Expand All @@ -2130,7 +2129,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v)
}
case TCP_SEQ_STATE_LISTENING:
if (v != SEQ_START_TOKEN)
inet_listen_unlock(&tcp_hashinfo);
spin_unlock_bh(&tcp_hashinfo.listening_hash[st->bucket].lock);
break;
case TCP_SEQ_STATE_TIME_WAIT:
case TCP_SEQ_STATE_ESTABLISHED:
Expand Down Expand Up @@ -2405,6 +2404,7 @@ static struct pernet_operations __net_initdata tcp_sk_ops = {

void __init tcp_v4_init(void)
{
inet_hashinfo_init(&tcp_hashinfo);
if (register_pernet_device(&tcp_sk_ops))
panic("Failed to create the TCP control socket.\n");
}
Expand Down
Loading

0 comments on commit 5caea4e

Please sign in to comment.