1/*
2 * IPVS:        Weighted Least-Connection Scheduling module
3 *
4 * Version:     $Id: ip_vs_wlc.c,v 1.1.1.1 2007/08/03 18:53:52 Exp $
5 *
6 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
7 *              Peter Kese <peter.kese@ijs.si>
8 *
9 *              This program is free software; you can redistribute it and/or
10 *              modify it under the terms of the GNU General Public License
11 *              as published by the Free Software Foundation; either version
12 *              2 of the License, or (at your option) any later version.
13 *
14 * Changes:
15 *     Wensong Zhang            :     changed the ip_vs_wlc_schedule to return dest
16 *     Wensong Zhang            :     changed to use the inactconns in scheduling
17 *     Wensong Zhang            :     changed some comestics things for debugging
18 *     Wensong Zhang            :     changed for the d-linked destination list
19 *     Wensong Zhang            :     added the ip_vs_wlc_update_svc
20 *     Wensong Zhang            :     added any dest with weight=0 is quiesced
21 *
22 */
23
24#include <linux/module.h>
25#include <linux/kernel.h>
26
27#include <net/ip_vs.h>
28
29
30static int
31ip_vs_wlc_init_svc(struct ip_vs_service *svc)
32{
33	return 0;
34}
35
36
37static int
38ip_vs_wlc_done_svc(struct ip_vs_service *svc)
39{
40	return 0;
41}
42
43
44static int
45ip_vs_wlc_update_svc(struct ip_vs_service *svc)
46{
47	return 0;
48}
49
50
51static inline unsigned int
52ip_vs_wlc_dest_overhead(struct ip_vs_dest *dest)
53{
54	/*
55	 * We think the overhead of processing active connections is 256
56	 * times higher than that of inactive connections in average. (This
57	 * 256 times might not be accurate, we will change it later) We
58	 * use the following formula to estimate the overhead now:
59	 *		  dest->activeconns*256 + dest->inactconns
60	 */
61	return (atomic_read(&dest->activeconns) << 8) +
62		atomic_read(&dest->inactconns);
63}
64
65
66/*
67 *	Weighted Least Connection scheduling
68 */
69static struct ip_vs_dest *
70ip_vs_wlc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
71{
72	struct ip_vs_dest *dest, *least;
73	unsigned int loh, doh;
74
75	IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");
76
77	/*
78	 * We calculate the load of each dest server as follows:
79	 *		  (dest overhead) / dest->weight
80	 *
81	 * Remember -- no floats in kernel mode!!!
82	 * The comparison of h1*w2 > h2*w1 is equivalent to that of
83	 *		  h1/w1 > h2/w2
84	 * if every weight is larger than zero.
85	 *
86	 * The server with weight=0 is quiesced and will not receive any
87	 * new connections.
88	 */
89
90	list_for_each_entry(dest, &svc->destinations, n_list) {
91		if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
92		    atomic_read(&dest->weight) > 0) {
93			least = dest;
94			loh = ip_vs_wlc_dest_overhead(least);
95			goto nextstage;
96		}
97	}
98	return NULL;
99
100	/*
101	 *    Find the destination with the least load.
102	 */
103  nextstage:
104	list_for_each_entry_continue(dest, &svc->destinations, n_list) {
105		if (dest->flags & IP_VS_DEST_F_OVERLOAD)
106			continue;
107		doh = ip_vs_wlc_dest_overhead(dest);
108		if (loh * atomic_read(&dest->weight) >
109		    doh * atomic_read(&least->weight)) {
110			least = dest;
111			loh = doh;
112		}
113	}
114
115	IP_VS_DBG(6, "WLC: server %u.%u.%u.%u:%u "
116		  "activeconns %d refcnt %d weight %d overhead %d\n",
117		  NIPQUAD(least->addr), ntohs(least->port),
118		  atomic_read(&least->activeconns),
119		  atomic_read(&least->refcnt),
120		  atomic_read(&least->weight), loh);
121
122	return least;
123}
124
125
126static struct ip_vs_scheduler ip_vs_wlc_scheduler =
127{
128	.name =			"wlc",
129	.refcnt =		ATOMIC_INIT(0),
130	.module =		THIS_MODULE,
131	.init_service =		ip_vs_wlc_init_svc,
132	.done_service =		ip_vs_wlc_done_svc,
133	.update_service =	ip_vs_wlc_update_svc,
134	.schedule =		ip_vs_wlc_schedule,
135};
136
137
138static int __init ip_vs_wlc_init(void)
139{
140	INIT_LIST_HEAD(&ip_vs_wlc_scheduler.n_list);
141	return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
142}
143
144static void __exit ip_vs_wlc_cleanup(void)
145{
146	unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
147}
148
149module_init(ip_vs_wlc_init);
150module_exit(ip_vs_wlc_cleanup);
151MODULE_LICENSE("GPL");
152