2 * IPVS: Weighted Round-Robin Scheduling module
4 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 * Wensong Zhang : changed the ip_vs_wrr_schedule to return dest
13 * Wensong Zhang : changed some comestics things for debugging
14 * Wensong Zhang : changed for the d-linked destination list
15 * Wensong Zhang : added the ip_vs_wrr_update_svc
16 * Julian Anastasov : fixed the bug of returning destination
17 * with weight 0 when all weights are zero
21 #define KMSG_COMPONENT "IPVS"
22 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
24 #include <linux/module.h>
25 #include <linux/kernel.h>
26 #include <linux/net.h>
28 #include <net/ip_vs.h>
31 * current destination pointer for weighted round-robin scheduling
33 struct ip_vs_wrr_mark
{
34 struct list_head
*cl
; /* current list head */
35 int cw
; /* current weight */
36 int mw
; /* maximum weight */
37 int di
; /* decreasing interval */
42 * Get the gcd of server weights
44 static int gcd(int a
, int b
)
55 static int ip_vs_wrr_gcd_weight(struct ip_vs_service
*svc
)
57 struct ip_vs_dest
*dest
;
61 list_for_each_entry(dest
, &svc
->destinations
, n_list
) {
62 weight
= atomic_read(&dest
->weight
);
75 * Get the maximum weight of the service destinations.
77 static int ip_vs_wrr_max_weight(struct ip_vs_service
*svc
)
79 struct ip_vs_dest
*dest
;
82 list_for_each_entry(dest
, &svc
->destinations
, n_list
) {
83 if (atomic_read(&dest
->weight
) > weight
)
84 weight
= atomic_read(&dest
->weight
);
91 static int ip_vs_wrr_init_svc(struct ip_vs_service
*svc
)
93 struct ip_vs_wrr_mark
*mark
;
96 * Allocate the mark variable for WRR scheduling
98 mark
= kmalloc(sizeof(struct ip_vs_wrr_mark
), GFP_ATOMIC
);
100 IP_VS_ERR("ip_vs_wrr_init_svc(): no memory\n");
103 mark
->cl
= &svc
->destinations
;
105 mark
->mw
= ip_vs_wrr_max_weight(svc
);
106 mark
->di
= ip_vs_wrr_gcd_weight(svc
);
107 svc
->sched_data
= mark
;
113 static int ip_vs_wrr_done_svc(struct ip_vs_service
*svc
)
116 * Release the mark variable
118 kfree(svc
->sched_data
);
124 static int ip_vs_wrr_update_svc(struct ip_vs_service
*svc
)
126 struct ip_vs_wrr_mark
*mark
= svc
->sched_data
;
128 mark
->cl
= &svc
->destinations
;
129 mark
->mw
= ip_vs_wrr_max_weight(svc
);
130 mark
->di
= ip_vs_wrr_gcd_weight(svc
);
131 if (mark
->cw
> mark
->mw
)
138 * Weighted Round-Robin Scheduling
140 static struct ip_vs_dest
*
141 ip_vs_wrr_schedule(struct ip_vs_service
*svc
, const struct sk_buff
*skb
)
143 struct ip_vs_dest
*dest
;
144 struct ip_vs_wrr_mark
*mark
= svc
->sched_data
;
147 IP_VS_DBG(6, "ip_vs_wrr_schedule(): Scheduling...\n");
150 * This loop will always terminate, because mark->cw in (0, max_weight]
151 * and at least one server has its weight equal to max_weight.
153 write_lock(&svc
->sched_lock
);
156 if (mark
->cl
== &svc
->destinations
) {
157 /* it is at the head of the destination list */
159 if (mark
->cl
== mark
->cl
->next
) {
161 IP_VS_ERR_RL("WRR: no destination available: "
162 "no destinations present\n");
167 mark
->cl
= svc
->destinations
.next
;
168 mark
->cw
-= mark
->di
;
172 * Still zero, which means no available servers.
175 mark
->cl
= &svc
->destinations
;
176 IP_VS_ERR_RL("WRR: no destination "
183 mark
->cl
= mark
->cl
->next
;
185 if (mark
->cl
!= &svc
->destinations
) {
186 /* not at the head of the list */
187 dest
= list_entry(mark
->cl
, struct ip_vs_dest
, n_list
);
188 if (!(dest
->flags
& IP_VS_DEST_F_OVERLOAD
) &&
189 atomic_read(&dest
->weight
) >= mark
->cw
) {
195 if (mark
->cl
== p
&& mark
->cw
== mark
->di
) {
196 /* back to the start, and no dest is found.
197 It is only possible when all dests are OVERLOADED */
199 IP_VS_ERR_RL("WRR: no destination available: "
200 "all destinations are overloaded\n");
205 IP_VS_DBG_BUF(6, "WRR: server %s:%u "
206 "activeconns %d refcnt %d weight %d\n",
207 IP_VS_DBG_ADDR(svc
->af
, &dest
->addr
), ntohs(dest
->port
),
208 atomic_read(&dest
->activeconns
),
209 atomic_read(&dest
->refcnt
),
210 atomic_read(&dest
->weight
));
213 write_unlock(&svc
->sched_lock
);
218 static struct ip_vs_scheduler ip_vs_wrr_scheduler
= {
220 .refcnt
= ATOMIC_INIT(0),
221 .module
= THIS_MODULE
,
222 .n_list
= LIST_HEAD_INIT(ip_vs_wrr_scheduler
.n_list
),
223 .init_service
= ip_vs_wrr_init_svc
,
224 .done_service
= ip_vs_wrr_done_svc
,
225 .update_service
= ip_vs_wrr_update_svc
,
226 .schedule
= ip_vs_wrr_schedule
,
229 static int __init
ip_vs_wrr_init(void)
231 return register_ip_vs_scheduler(&ip_vs_wrr_scheduler
) ;
234 static void __exit
ip_vs_wrr_cleanup(void)
236 unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler
);
239 module_init(ip_vs_wrr_init
);
240 module_exit(ip_vs_wrr_cleanup
);
241 MODULE_LICENSE("GPL");