Commit 85f66df3 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

Merge branch 'tcp-scale-connect-under-pressure' 

Eric Dumazet says:

====================
tcp: scale connect() under pressure

Adoption of bhash2 in linux-6.1 made some operations almost twice
more expensive, because of additional locks.

This series adds RCU in __inet_hash_connect() to help the
case where many attempts need to be made before finding
an available 4-tuple.

This brings a ~200 % improvement in this experiment:

Server:
ulimit -n 40000; neper/tcp_crr -T 200 -F 30000 -6 --nolog

Client:
ulimit -n 40000; neper/tcp_crr -T 200 -F 30000 -6 --nolog -c -H server

Before series:

  utime_start=0.288582
  utime_end=1.548707
  stime_start=20.637138
  stime_end=2002.489845
  num_transactions=484453
  latency_min=0.156279245
  latency_max=20.922042756
  latency_mean=1.546521274
  latency_stddev=3.936005194
  num_samples=312537
  throughput=47426.00

perf top on the client:

 49.54%  [kernel]       [k] _raw_spin_lock
 25.87%  [kernel]       [k] _raw_spin_lock_bh
  5.97%  [kernel]       [k] queued_spin_lock_slowpath
  5.67%  [kernel]       [k] __inet_hash_connect
  3.53%  [kernel]       [k] __inet6_check_established
  3.48%  [kernel]       [k] inet6_ehashfn
  0.64%  [kernel]       [k] rcu_all_qs

After this series:

  utime_start=0.271607
  utime_end=3.847111
  stime_start=18.407684
  stime_end=1997.485557
  num_transactions=1350742
  latency_min=0.014131929
  latency_max=17.895073144
  latency_mean=0.505675853   # Nice reduction of latency metrics
  latency_stddev=2.125164772
  num_samples=307884
  throughput=139866.80       # 194 % increase

perf top on client:

 56.86%  [kernel]       [k] __inet6_check_established
 17.96%  [kernel]       [k] __inet_hash_connect
 13.88%  [kernel]       [k] inet6_ehashfn
  2.52%  [kernel]       [k] rcu_all_qs
  2.01%  [kernel]       [k] __cond_resched
  0.41%  [kernel]       [k] _raw_spin_lock
====================

Link: https://patch.msgid.link/20250302124237.3913746-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parents 7ff1c88f 86c2bc29

include/net/inet_hashtables.h

+4 −3
Original line number Diff line number Diff line
@@ -89,6 +89,7 @@ struct inet_bind_bucket { 
	bool			fast_ipv6_only;

	struct hlist_node	node;

	struct hlist_head	bhash2;

	struct rcu_head		rcu;

};



struct inet_bind2_bucket {
@@ -226,8 +227,7 @@ struct inet_bind_bucket * 
inet_bind_bucket_create(struct kmem_cache *cachep, struct net *net,

			struct inet_bind_hashbucket *head,

			const unsigned short snum, int l3mdev);

void inet_bind_bucket_destroy(struct kmem_cache *cachep,

			      struct inet_bind_bucket *tb);

void inet_bind_bucket_destroy(struct inet_bind_bucket *tb);



bool inet_bind_bucket_match(const struct inet_bind_bucket *tb,

			    const struct net *net, unsigned short port,
@@ -529,7 +529,8 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, 
			struct sock *sk, u64 port_offset,

			int (*check_established)(struct inet_timewait_death_row *,

						 struct sock *, __u16,

						 struct inet_timewait_sock **));

						 struct inet_timewait_sock **,

						 bool rcu_lookup));



int inet_hash_connect(struct inet_timewait_death_row *death_row,

		      struct sock *sk);

net/ipv4/inet_connection_sock.c

+3 −5
Original line number Diff line number Diff line
@@ -157,12 +157,10 @@ static bool inet_use_bhash2_on_bind(const struct sock *sk) 
{

#if IS_ENABLED(CONFIG_IPV6)

	if (sk->sk_family == AF_INET6) {

		int addr_type = ipv6_addr_type(&sk->sk_v6_rcv_saddr);



		if (addr_type == IPV6_ADDR_ANY)

		if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))

			return false;



		if (addr_type != IPV6_ADDR_MAPPED)

		if (!ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))

			return true;

	}

#endif
@@ -600,7 +598,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum) 
		if (bhash2_created)

			inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep, tb2);

		if (bhash_created)

			inet_bind_bucket_destroy(hinfo->bind_bucket_cachep, tb);

			inet_bind_bucket_destroy(tb);

	}

	if (head2_lock_acquired)

		spin_unlock(&head2->lock);

net/ipv4/inet_hashtables.c

+48 −17
Original line number Diff line number Diff line
@@ -76,7 +76,7 @@ struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep, 
		tb->fastreuse = 0;

		tb->fastreuseport = 0;

		INIT_HLIST_HEAD(&tb->bhash2);

		hlist_add_head(&tb->node, &head->chain);

		hlist_add_head_rcu(&tb->node, &head->chain);

	}

	return tb;

}
@@ -84,11 +84,11 @@ struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep, 
/*

 * Caller must hold hashbucket lock for this tb with local BH disabled

 */

void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)

void inet_bind_bucket_destroy(struct inet_bind_bucket *tb)

{

	if (hlist_empty(&tb->bhash2)) {

		__hlist_del(&tb->node);

		kmem_cache_free(cachep, tb);

		hlist_del_rcu(&tb->node);

		kfree_rcu(tb, rcu);

	}

}
@@ -201,7 +201,7 @@ static void __inet_put_port(struct sock *sk) 
	}

	spin_unlock(&head2->lock);



	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);

	inet_bind_bucket_destroy(tb);

	spin_unlock(&head->lock);

}
@@ -285,7 +285,7 @@ int __inet_inherit_port(const struct sock *sk, struct sock *child) 


error:

	if (created_inet_bind_bucket)

		inet_bind_bucket_destroy(table->bind_bucket_cachep, tb);

		inet_bind_bucket_destroy(tb);

	spin_unlock(&head2->lock);

	spin_unlock(&head->lock);

	return -ENOMEM;
@@ -537,7 +537,8 @@ EXPORT_SYMBOL_GPL(__inet_lookup_established); 
/* called with local bh disabled */

static int __inet_check_established(struct inet_timewait_death_row *death_row,

				    struct sock *sk, __u16 lport,

				    struct inet_timewait_sock **twp)

				    struct inet_timewait_sock **twp,

				    bool rcu_lookup)

{

	struct inet_hashinfo *hinfo = death_row->hashinfo;

	struct inet_sock *inet = inet_sk(sk);
@@ -551,11 +552,24 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row, 
	unsigned int hash = inet_ehashfn(net, daddr, lport,

					 saddr, inet->inet_dport);

	struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);

	spinlock_t *lock = inet_ehash_lockp(hinfo, hash);

	struct sock *sk2;

	const struct hlist_nulls_node *node;

	struct inet_timewait_sock *tw = NULL;

	const struct hlist_nulls_node *node;

	struct sock *sk2;

	spinlock_t *lock;



	if (rcu_lookup) {

		sk_nulls_for_each(sk2, node, &head->chain) {

			if (sk2->sk_hash != hash ||

			    !inet_match(net, sk2, acookie, ports, dif, sdif))

				continue;

			if (sk2->sk_state == TCP_TIME_WAIT)

				break;

			return -EADDRNOTAVAIL;

		}

		return 0;

	}



	lock = inet_ehash_lockp(hinfo, hash);

	spin_lock(lock);



	sk_nulls_for_each(sk2, node, &head->chain) {
@@ -994,7 +1008,8 @@ static u32 *table_perturb; 
int __inet_hash_connect(struct inet_timewait_death_row *death_row,

		struct sock *sk, u64 port_offset,

		int (*check_established)(struct inet_timewait_death_row *,

			struct sock *, __u16, struct inet_timewait_sock **))

			struct sock *, __u16, struct inet_timewait_sock **,

			bool rcu_lookup))

{

	struct inet_hashinfo *hinfo = death_row->hashinfo;

	struct inet_bind_hashbucket *head, *head2;
@@ -1012,7 +1027,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, 


	if (port) {

		local_bh_disable();

		ret = check_established(death_row, sk, port, NULL);

		ret = check_established(death_row, sk, port, NULL, false);

		local_bh_enable();

		return ret;

	}
@@ -1048,6 +1063,21 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, 
			continue;

		head = &hinfo->bhash[inet_bhashfn(net, port,

						  hinfo->bhash_size)];

		rcu_read_lock();

		hlist_for_each_entry_rcu(tb, &head->chain, node) {

			if (!inet_bind_bucket_match(tb, net, port, l3mdev))

				continue;

			if (tb->fastreuse >= 0 || tb->fastreuseport >= 0) {

				rcu_read_unlock();

				goto next_port;

			}

			if (!check_established(death_row, sk, port, &tw, true))

				break;

			rcu_read_unlock();

			goto next_port;

		}

		rcu_read_unlock();



		spin_lock_bh(&head->lock);



		/* Does not bother with rcv_saddr checks, because
@@ -1057,12 +1087,12 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, 
			if (inet_bind_bucket_match(tb, net, port, l3mdev)) {

				if (tb->fastreuse >= 0 ||

				    tb->fastreuseport >= 0)

					goto next_port;

					goto next_port_unlock;

				WARN_ON(hlist_empty(&tb->bhash2));

				if (!check_established(death_row, sk,

						       port, &tw))

						       port, &tw, false))

					goto ok;

				goto next_port;

				goto next_port_unlock;

			}

		}
@@ -1076,8 +1106,9 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, 
		tb->fastreuse = -1;

		tb->fastreuseport = -1;

		goto ok;

next_port:

next_port_unlock:

		spin_unlock_bh(&head->lock);

next_port:

		cond_resched();

	}
@@ -1149,7 +1180,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, 


	spin_unlock(&head2->lock);

	if (tb_created)

		inet_bind_bucket_destroy(hinfo->bind_bucket_cachep, tb);

		inet_bind_bucket_destroy(tb);

	spin_unlock(&head->lock);



	if (tw)

net/ipv4/inet_timewait_sock.c

+1 −1
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ void inet_twsk_bind_unhash(struct inet_timewait_sock *tw, 
	tw->tw_tb = NULL;

	tw->tw_tb2 = NULL;

	inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);

	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);

	inet_bind_bucket_destroy(tb);



	__sock_put((struct sock *)tw);

}

net/ipv6/inet6_hashtables.c

+19 −4
Original line number Diff line number Diff line
@@ -263,7 +263,8 @@ EXPORT_SYMBOL_GPL(inet6_lookup); 


static int __inet6_check_established(struct inet_timewait_death_row *death_row,

				     struct sock *sk, const __u16 lport,

				     struct inet_timewait_sock **twp)

				     struct inet_timewait_sock **twp,

				     bool rcu_lookup)

{

	struct inet_hashinfo *hinfo = death_row->hashinfo;

	struct inet_sock *inet = inet_sk(sk);
@@ -276,11 +277,25 @@ static int __inet6_check_established(struct inet_timewait_death_row *death_row, 
	const unsigned int hash = inet6_ehashfn(net, daddr, lport, saddr,

						inet->inet_dport);

	struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);

	spinlock_t *lock = inet_ehash_lockp(hinfo, hash);

	struct sock *sk2;

	const struct hlist_nulls_node *node;

	struct inet_timewait_sock *tw = NULL;

	const struct hlist_nulls_node *node;

	struct sock *sk2;

	spinlock_t *lock;



	if (rcu_lookup) {

		sk_nulls_for_each(sk2, node, &head->chain) {

			if (sk2->sk_hash != hash ||

			    !inet6_match(net, sk2, saddr, daddr,

					 ports, dif, sdif))

				continue;

			if (sk2->sk_state == TCP_TIME_WAIT)

				break;

			return -EADDRNOTAVAIL;

		}

		return 0;

	}



	lock = inet_ehash_lockp(hinfo, hash);

	spin_lock(lock);



	sk_nulls_for_each(sk2, node, &head->chain) {