[IPV4]: reset IPCB flags when neccessary
[linux-2.6] / net / ipv4 / ipvs / ip_vs_wlc.c
1 /*
2  * IPVS:        Weighted Least-Connection Scheduling module
3  *
4  * Version:     $Id: ip_vs_wlc.c,v 1.13 2003/04/18 09:03:16 wensong 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
30 static int
31 ip_vs_wlc_init_svc(struct ip_vs_service *svc)
32 {
33         return 0;
34 }
35
36
37 static int
38 ip_vs_wlc_done_svc(struct ip_vs_service *svc)
39 {
40         return 0;
41 }
42
43
44 static int
45 ip_vs_wlc_update_svc(struct ip_vs_service *svc)
46 {
47         return 0;
48 }
49
50
51 static inline unsigned int
52 ip_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  */
69 static struct ip_vs_dest *
70 ip_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
126 static 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
138 static 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
144 static void __exit ip_vs_wlc_cleanup(void)
145 {
146         unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
147 }
148
149 module_init(ip_vs_wlc_init);
150 module_exit(ip_vs_wlc_cleanup);
151 MODULE_LICENSE("GPL");