1/*
2 * IPVS:        Least-Connection Scheduling module
3 *
4 * Version:     $Id: ip_vs_lc.c,v 1.1.1.1 2007/08/03 18:53:51 Exp $
5 *
6 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
7 *
8 *              This program is free software; you can redistribute it and/or
9 *              modify it under the terms of the GNU General Public License
10 *              as published by the Free Software Foundation; either version
11 *              2 of the License, or (at your option) any later version.
12 *
13 * Changes:
14 *     Wensong Zhang            :     added the ip_vs_lc_update_svc
15 *     Wensong Zhang            :     added any dest with weight=0 is quiesced
16 *
17 */
18
19#include <linux/module.h>
20#include <linux/kernel.h>
21
22#include <net/ip_vs.h>
23
24
25static int ip_vs_lc_init_svc(struct ip_vs_service *svc)
26{
27	return 0;
28}
29
30
31static int ip_vs_lc_done_svc(struct ip_vs_service *svc)
32{
33	return 0;
34}
35
36
37static int ip_vs_lc_update_svc(struct ip_vs_service *svc)
38{
39	return 0;
40}
41
42
43static inline unsigned int
44ip_vs_lc_dest_overhead(struct ip_vs_dest *dest)
45{
46	/*
47	 * We think the overhead of processing active connections is 256
48	 * times higher than that of inactive connections in average. (This
49	 * 256 times might not be accurate, we will change it later) We
50	 * use the following formula to estimate the overhead now:
51	 *		  dest->activeconns*256 + dest->inactconns
52	 */
53	return (atomic_read(&dest->activeconns) << 8) +
54		atomic_read(&dest->inactconns);
55}
56
57
58/*
59 *	Least Connection scheduling
60 */
61static struct ip_vs_dest *
62ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
63{
64	struct ip_vs_dest *dest, *least = NULL;
65	unsigned int loh = 0, doh;
66
67	IP_VS_DBG(6, "ip_vs_lc_schedule(): Scheduling...\n");
68
69	/*
70	 * Simply select the server with the least number of
71	 *        (activeconns<<5) + inactconns
72	 * Except whose weight is equal to zero.
73	 * If the weight is equal to zero, it means that the server is
74	 * quiesced, the existing connections to the server still get
75	 * served, but no new connection is assigned to the server.
76	 */
77
78	list_for_each_entry(dest, &svc->destinations, n_list) {
79		if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
80		    atomic_read(&dest->weight) == 0)
81			continue;
82		doh = ip_vs_lc_dest_overhead(dest);
83		if (!least || doh < loh) {
84			least = dest;
85			loh = doh;
86		}
87	}
88
89	if (least)
90	IP_VS_DBG(6, "LC: server %u.%u.%u.%u:%u activeconns %d inactconns %d\n",
91		  NIPQUAD(least->addr), ntohs(least->port),
92		  atomic_read(&least->activeconns),
93		  atomic_read(&least->inactconns));
94
95	return least;
96}
97
98
99static struct ip_vs_scheduler ip_vs_lc_scheduler = {
100	.name =			"lc",
101	.refcnt =		ATOMIC_INIT(0),
102	.module =		THIS_MODULE,
103	.init_service =		ip_vs_lc_init_svc,
104	.done_service =		ip_vs_lc_done_svc,
105	.update_service =	ip_vs_lc_update_svc,
106	.schedule =		ip_vs_lc_schedule,
107};
108
109
110static int __init ip_vs_lc_init(void)
111{
112	INIT_LIST_HEAD(&ip_vs_lc_scheduler.n_list);
113	return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
114}
115
116static void __exit ip_vs_lc_cleanup(void)
117{
118	unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
119}
120
121module_init(ip_vs_lc_init);
122module_exit(ip_vs_lc_cleanup);
123MODULE_LICENSE("GPL");
124