linux/net/core/request_sock.c
Peter Pan(潘卫平) 99b53bdd81 ipv4:correct description for tcp_max_syn_backlog
Since commit c5ed63d66f24(tcp: fix three tcp sysctls tuning),
sysctl_max_syn_backlog is determined by tcp_hashinfo->ehash_mask,
and the minimal value is 128, and it will increase in proportion to the
memory of machine.
The original description for tcp_max_syn_backlog and sysctl_max_syn_backlog
are out of date.

Changelog:
V2: update description for sysctl_max_syn_backlog

Signed-off-by: Weiping Pan <panweiping3@gmail.com>
Reviewed-by: Shan Wei <shanwei88@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-12-06 13:02:28 -05:00

132 lines
3.5 KiB
C

/*
* NET Generic infrastructure for Network protocols.
*
* Authors: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
*
* From code originally in include/net/tcp.h
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <net/request_sock.h>
/*
* Maximum number of SYN_RECV sockets in queue per LISTEN socket.
* One SYN_RECV socket costs about 80bytes on a 32bit machine.
* It would be better to replace it with a global counter for all sockets
* but then some measure against one socket starving all other sockets
* would be needed.
*
* The minimum value of it is 128. Experiments with real servers show that
* it is absolutely not enough even at 100conn/sec. 256 cures most
* of problems.
* This value is adjusted to 128 for low memory machines,
* and it will increase in proportion to the memory of machine.
* Note : Dont forget somaxconn that may limit backlog too.
*/
int sysctl_max_syn_backlog = 256;
EXPORT_SYMBOL(sysctl_max_syn_backlog);
int reqsk_queue_alloc(struct request_sock_queue *queue,
unsigned int nr_table_entries)
{
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 = vzalloc(lopt_size);
else
lopt = kzalloc(lopt_size, GFP_KERNEL);
if (lopt == NULL)
return -ENOMEM;
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));
rwlock_init(&queue->syn_wait_lock);
queue->rskq_accept_head = NULL;
lopt->nr_table_entries = nr_table_entries;
write_lock_bh(&queue->syn_wait_lock);
queue->listen_opt = lopt;
write_unlock_bh(&queue->syn_wait_lock);
return 0;
}
void __reqsk_queue_destroy(struct request_sock_queue *queue)
{
struct listen_sock *lopt;
size_t lopt_size;
/*
* this is an error recovery path only
* no locking needed and the lopt is not NULL
*/
lopt = queue->listen_opt;
lopt_size = sizeof(struct listen_sock) +
lopt->nr_table_entries * sizeof(struct request_sock *);
if (lopt_size > PAGE_SIZE)
vfree(lopt);
else
kfree(lopt);
}
static inline struct listen_sock *reqsk_queue_yank_listen_sk(
struct request_sock_queue *queue)
{
struct listen_sock *lopt;
write_lock_bh(&queue->syn_wait_lock);
lopt = queue->listen_opt;
queue->listen_opt = NULL;
write_unlock_bh(&queue->syn_wait_lock);
return lopt;
}
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) {
unsigned int i;
for (i = 0; i < lopt->nr_table_entries; i++) {
struct request_sock *req;
while ((req = lopt->syn_table[i]) != NULL) {
lopt->syn_table[i] = req->dl_next;
lopt->qlen--;
reqsk_free(req);
}
}
}
WARN_ON(lopt->qlen != 0);
if (lopt_size > PAGE_SIZE)
vfree(lopt);
else
kfree(lopt);
}