ip_vs_lc.c

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * IPVS:        Least-Connection Scheduling module
 4 *
 5 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 6 *
 7 * Changes:
 8 *     Wensong Zhang            :     added the ip_vs_lc_update_svc
 9 *     Wensong Zhang            :     added any dest with weight=0 is quiesced
10 */
11
12#define pr_fmt(fmt) "IPVS: " fmt
13
14#include <linux/module.h>
15#include <linux/kernel.h>
16
17#include <net/ip_vs.h>
18
19/*
20 *	Least Connection scheduling
21 */
22static struct ip_vs_dest *
23ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
24		  struct ip_vs_iphdr *iph)
25{
26	struct ip_vs_dest *dest, *least = NULL;
27	unsigned int loh = 0, doh;
28
29	IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
30
31	/*
32	 * Simply select the server with the least number of
33	 *        (activeconns<<5) + inactconns
34	 * Except whose weight is equal to zero.
35	 * If the weight is equal to zero, it means that the server is
36	 * quiesced, the existing connections to the server still get
37	 * served, but no new connection is assigned to the server.
38	 */
39
40	list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
41		if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
42		    atomic_read(&dest->weight) == 0)
43			continue;
44		doh = ip_vs_dest_conn_overhead(dest);
45		if (!least || doh < loh) {
46			least = dest;
47			loh = doh;
48		}
49	}
50
51	if (!least)
52		ip_vs_scheduler_err(svc, "no destination available");
53	else
54		IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
55			      "inactconns %d\n",
56			      IP_VS_DBG_ADDR(least->af, &least->addr),
57			      ntohs(least->port),
58			      atomic_read(&least->activeconns),
59			      atomic_read(&least->inactconns));
60
61	return least;
62}
63
64
65static struct ip_vs_scheduler ip_vs_lc_scheduler = {
66	.name =			"lc",
67	.refcnt =		ATOMIC_INIT(0),
68	.module =		THIS_MODULE,
69	.n_list =		LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
70	.schedule =		ip_vs_lc_schedule,
71};
72
73
74static int __init ip_vs_lc_init(void)
75{
76	return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
77}
78
79static void __exit ip_vs_lc_cleanup(void)
80{
81	unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
82	synchronize_rcu();
83}
84
85module_init(ip_vs_lc_init);
86module_exit(ip_vs_lc_cleanup);
87MODULE_LICENSE("GPL");
88MODULE_DESCRIPTION("ipvs least connection scheduler");