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Commit 72a3effa authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

[NET]: Size listen hash tables using backlog hint 



We currently allocate a fixed size (TCP_SYNQ_HSIZE=512) slots hash table for
each LISTEN socket, regardless of various parameters (listen backlog for
example)

On x86_64, this means order-1 allocations (might fail), even for 'small'
sockets, expecting few connections. On the contrary, a huge server wanting a
backlog of 50000 is slowed down a bit because of this fixed limit.

This patch makes the sizing of listen hash table a dynamic parameter,
depending of :
- net.core.somaxconn tunable (default is 128)
- net.ipv4.tcp_max_syn_backlog tunable (default : 256, 1024 or 128)
- backlog value given by user application  (2nd parameter of listen())

For large allocations (bigger than PAGE_SIZE), we use vmalloc() instead of
kmalloc().

We still limit memory allocation with the two existing tunables (somaxconn &
tcp_max_syn_backlog). So for standard setups, this patch actually reduce RAM
usage.

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3c62f75a

include/net/request_sock.h

+4 −4
Original line number Diff line number Diff line
@@ -28,8 +28,8 @@ struct proto; 


struct request_sock_ops {

	int		family;

	kmem_cache_t	*slab;

	int		obj_size;

	kmem_cache_t	*slab;

	int		(*rtx_syn_ack)(struct sock *sk,

				       struct request_sock *req,

				       struct dst_entry *dst);
@@ -51,13 +51,13 @@ struct request_sock { 
	u32				rcv_wnd;	  /* rcv_wnd offered first time */

	u32				ts_recent;

	unsigned long			expires;

	struct request_sock_ops		*rsk_ops;

	const struct request_sock_ops	*rsk_ops;

	struct sock			*sk;

	u32				secid;

	u32				peer_secid;

};



static inline struct request_sock *reqsk_alloc(struct request_sock_ops *ops)

static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)

{

	struct request_sock *req = kmem_cache_alloc(ops->slab, SLAB_ATOMIC);
@@ -121,7 +121,7 @@ struct request_sock_queue { 
};



extern int reqsk_queue_alloc(struct request_sock_queue *queue,

			     const int nr_table_entries);

			     unsigned int nr_table_entries);



static inline struct listen_sock *reqsk_queue_yank_listen_sk(struct request_sock_queue *queue)

{

include/net/tcp.h

+0 −1
Original line number Diff line number Diff line
@@ -138,7 +138,6 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo); 
#define MAX_TCP_SYNCNT		127



#define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */

#define TCP_SYNQ_HSIZE		512	/* Size of SYNACK hash table */



#define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)

#define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated

net/core/request_sock.c

+25 −10
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/random.h>

#include <linux/slab.h>

#include <linux/string.h>

#include <linux/vmalloc.h>



#include <net/request_sock.h>
@@ -29,22 +30,31 @@ 
 * it is absolutely not enough even at 100conn/sec. 256 cures most

 * of problems. This value is adjusted to 128 for very small machines

 * (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb).

 * Further increasing requires to change hash table size.

 * Note : Dont forget somaxconn that may limit backlog too.

 */

int sysctl_max_syn_backlog = 256;



int reqsk_queue_alloc(struct request_sock_queue *queue,

		      const int nr_table_entries)

		      unsigned int nr_table_entries)

{

	const int lopt_size = sizeof(struct listen_sock) +

			      nr_table_entries * sizeof(struct request_sock *);

	struct listen_sock *lopt = kzalloc(lopt_size, GFP_KERNEL);



	size_t lopt_size = sizeof(struct listen_sock);

	struct listen_sock *lopt;



	nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);

	nr_table_entries = max_t(u32, nr_table_entries, 8);

	nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);

	lopt_size += nr_table_entries * sizeof(struct request_sock *);

	if (lopt_size > PAGE_SIZE)

		lopt = __vmalloc(lopt_size,

			GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,

			PAGE_KERNEL);

	else

		lopt = kzalloc(lopt_size, GFP_KERNEL);

	if (lopt == NULL)

		return -ENOMEM;



	for (lopt->max_qlen_log = 6;

	     (1 << lopt->max_qlen_log) < sysctl_max_syn_backlog;

	for (lopt->max_qlen_log = 3;

	     (1 << lopt->max_qlen_log) < nr_table_entries;

	     lopt->max_qlen_log++);



	get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
@@ -65,9 +75,11 @@ void reqsk_queue_destroy(struct request_sock_queue *queue) 
{

	/* make all the listen_opt local to us */

	struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);

	size_t lopt_size = sizeof(struct listen_sock) +

		lopt->nr_table_entries * sizeof(struct request_sock *);



	if (lopt->qlen != 0) {

		int i;

		unsigned int i;



		for (i = 0; i < lopt->nr_table_entries; i++) {

			struct request_sock *req;
@@ -81,6 +93,9 @@ void reqsk_queue_destroy(struct request_sock_queue *queue) 
	}



	BUG_TRAP(lopt->qlen == 0);

	if (lopt_size > PAGE_SIZE)

		vfree(lopt);

	else

		kfree(lopt);

}

net/dccp/ipv4.c

+1 −1
Original line number Diff line number Diff line
@@ -1022,7 +1022,7 @@ static void dccp_v4_reqsk_destructor(struct request_sock *req) 
	kfree(inet_rsk(req)->opt);

}



static struct request_sock_ops dccp_request_sock_ops = {

static struct request_sock_ops dccp_request_sock_ops _read_mostly = {

	.family		= PF_INET,

	.obj_size	= sizeof(struct dccp_request_sock),

	.rtx_syn_ack	= dccp_v4_send_response,

net/dccp/proto.c

+3 −3
Original line number Diff line number Diff line
@@ -262,12 +262,12 @@ int dccp_destroy_sock(struct sock *sk) 


EXPORT_SYMBOL_GPL(dccp_destroy_sock);



static inline int dccp_listen_start(struct sock *sk)

static inline int dccp_listen_start(struct sock *sk, int backlog)

{

	struct dccp_sock *dp = dccp_sk(sk);



	dp->dccps_role = DCCP_ROLE_LISTEN;

	return inet_csk_listen_start(sk, TCP_SYNQ_HSIZE);

	return inet_csk_listen_start(sk, backlog);

}



int dccp_disconnect(struct sock *sk, int flags)
@@ -788,7 +788,7 @@ int inet_dccp_listen(struct socket *sock, int backlog) 
		 * FIXME: here it probably should be sk->sk_prot->listen_start

		 * see tcp_listen_start

		 */

		err = dccp_listen_start(sk);

		err = dccp_listen_start(sk, backlog);

		if (err)

			goto out;

	}