2 * IPVS: Weighted Round-Robin Scheduling module
4 * Version: $Id: ip_vs_wrr.c,v 1.12 2002/09/15 08:14:08 wensong Exp $
6 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
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.
14 * Wensong Zhang : changed the ip_vs_wrr_schedule to return dest
15 * Wensong Zhang : changed some comestics things for debugging
16 * Wensong Zhang : changed for the d-linked destination list
17 * Wensong Zhang : added the ip_vs_wrr_update_svc
18 * Julian Anastasov : fixed the bug of returning destination
19 * with weight 0 when all weights are zero
23 #include <linux/module.h>
24 #include <linux/kernel.h>
26 #include <net/ip_vs.h>
29 * current destination pointer for weighted round-robin scheduling
31 struct ip_vs_wrr_mark {
32 struct list_head *cl; /* current list head */
33 int cw; /* current weight */
34 int mw; /* maximum weight */
35 int di; /* decreasing interval */
40 * Get the gcd of server weights
42 static int gcd(int a, int b)
53 static int ip_vs_wrr_gcd_weight(struct ip_vs_service *svc)
55 struct ip_vs_dest *dest;
59 list_for_each_entry(dest, &svc->destinations, n_list) {
60 weight = atomic_read(&dest->weight);
73 * Get the maximum weight of the service destinations.
75 static int ip_vs_wrr_max_weight(struct ip_vs_service *svc)
77 struct ip_vs_dest *dest;
80 list_for_each_entry(dest, &svc->destinations, n_list) {
81 if (atomic_read(&dest->weight) > weight)
82 weight = atomic_read(&dest->weight);
89 static int ip_vs_wrr_init_svc(struct ip_vs_service *svc)
91 struct ip_vs_wrr_mark *mark;
94 * Allocate the mark variable for WRR scheduling
96 mark = kmalloc(sizeof(struct ip_vs_wrr_mark), GFP_ATOMIC);
98 IP_VS_ERR("ip_vs_wrr_init_svc(): no memory\n");
101 mark->cl = &svc->destinations;
103 mark->mw = ip_vs_wrr_max_weight(svc);
104 mark->di = ip_vs_wrr_gcd_weight(svc);
105 svc->sched_data = mark;
111 static int ip_vs_wrr_done_svc(struct ip_vs_service *svc)
114 * Release the mark variable
116 kfree(svc->sched_data);
122 static int ip_vs_wrr_update_svc(struct ip_vs_service *svc)
124 struct ip_vs_wrr_mark *mark = svc->sched_data;
126 mark->cl = &svc->destinations;
127 mark->mw = ip_vs_wrr_max_weight(svc);
128 mark->di = ip_vs_wrr_gcd_weight(svc);
134 * Weighted Round-Robin Scheduling
136 static struct ip_vs_dest *
137 ip_vs_wrr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
139 struct ip_vs_dest *dest;
140 struct ip_vs_wrr_mark *mark = svc->sched_data;
143 IP_VS_DBG(6, "ip_vs_wrr_schedule(): Scheduling...\n");
146 * This loop will always terminate, because mark->cw in (0, max_weight]
147 * and at least one server has its weight equal to max_weight.
149 write_lock(&svc->sched_lock);
152 if (mark->cl == &svc->destinations) {
153 /* it is at the head of the destination list */
155 if (mark->cl == mark->cl->next) {
161 mark->cl = svc->destinations.next;
162 mark->cw -= mark->di;
166 * Still zero, which means no availabe servers.
169 mark->cl = &svc->destinations;
170 IP_VS_INFO("ip_vs_wrr_schedule(): "
171 "no available servers\n");
177 mark->cl = mark->cl->next;
179 if (mark->cl != &svc->destinations) {
180 /* not at the head of the list */
181 dest = list_entry(mark->cl, struct ip_vs_dest, n_list);
182 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
183 atomic_read(&dest->weight) >= mark->cw) {
190 /* back to the start, and no dest is found.
191 It is only possible when all dests are OVERLOADED */
197 IP_VS_DBG(6, "WRR: server %u.%u.%u.%u:%u "
198 "activeconns %d refcnt %d weight %d\n",
199 NIPQUAD(dest->addr), ntohs(dest->port),
200 atomic_read(&dest->activeconns),
201 atomic_read(&dest->refcnt),
202 atomic_read(&dest->weight));
205 write_unlock(&svc->sched_lock);
210 static struct ip_vs_scheduler ip_vs_wrr_scheduler = {
212 .refcnt = ATOMIC_INIT(0),
213 .module = THIS_MODULE,
214 .init_service = ip_vs_wrr_init_svc,
215 .done_service = ip_vs_wrr_done_svc,
216 .update_service = ip_vs_wrr_update_svc,
217 .schedule = ip_vs_wrr_schedule,
220 static int __init ip_vs_wrr_init(void)
222 INIT_LIST_HEAD(&ip_vs_wrr_scheduler.n_list);
223 return register_ip_vs_scheduler(&ip_vs_wrr_scheduler) ;
226 static void __exit ip_vs_wrr_cleanup(void)
228 unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler);
231 module_init(ip_vs_wrr_init);
232 module_exit(ip_vs_wrr_cleanup);
233 MODULE_LICENSE("GPL");