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
;
80 int new_weight
, weight
= 0;
82 list_for_each_entry(dest
, &svc
->destinations
, n_list
) {
83 new_weight
= atomic_read(&dest
->weight
);
84 if (new_weight
> weight
)
92 static int ip_vs_wrr_init_svc(struct ip_vs_service
*svc
)
94 struct ip_vs_wrr_mark
*mark
;
97 * Allocate the mark variable for WRR scheduling
99 mark
= kmalloc(sizeof(struct ip_vs_wrr_mark
), GFP_ATOMIC
);
101 pr_err("%s(): no memory\n", __func__
);
104 mark
->cl
= &svc
->destinations
;
106 mark
->mw
= ip_vs_wrr_max_weight(svc
);
107 mark
->di
= ip_vs_wrr_gcd_weight(svc
);
108 svc
->sched_data
= mark
;
114 static int ip_vs_wrr_done_svc(struct ip_vs_service
*svc
)
117 * Release the mark variable
119 kfree(svc
->sched_data
);
125 static int ip_vs_wrr_update_svc(struct ip_vs_service
*svc
)
127 struct ip_vs_wrr_mark
*mark
= svc
->sched_data
;
129 mark
->cl
= &svc
->destinations
;
130 mark
->mw
= ip_vs_wrr_max_weight(svc
);
131 mark
->di
= ip_vs_wrr_gcd_weight(svc
);
132 if (mark
->cw
> mark
->mw
)
139 * Weighted Round-Robin Scheduling
141 static struct ip_vs_dest
*
142 ip_vs_wrr_schedule(struct ip_vs_service
*svc
, const struct sk_buff
*skb
)
144 struct ip_vs_dest
*dest
;
145 struct ip_vs_wrr_mark
*mark
= svc
->sched_data
;
148 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__
);
151 * This loop will always terminate, because mark->cw in (0, max_weight]
152 * and at least one server has its weight equal to max_weight.
154 write_lock(&svc
->sched_lock
);
157 if (mark
->cl
== &svc
->destinations
) {
158 /* it is at the head of the destination list */
160 if (mark
->cl
== mark
->cl
->next
) {
162 IP_VS_ERR_RL("WRR: no destination available: "
163 "no destinations present\n");
168 mark
->cl
= svc
->destinations
.next
;
169 mark
->cw
-= mark
->di
;
173 * Still zero, which means no available servers.
176 mark
->cl
= &svc
->destinations
;
177 IP_VS_ERR_RL("WRR: no destination "
184 mark
->cl
= mark
->cl
->next
;
186 if (mark
->cl
!= &svc
->destinations
) {
187 /* not at the head of the list */
188 dest
= list_entry(mark
->cl
, struct ip_vs_dest
, n_list
);
189 if (!(dest
->flags
& IP_VS_DEST_F_OVERLOAD
) &&
190 atomic_read(&dest
->weight
) >= mark
->cw
) {
196 if (mark
->cl
== p
&& mark
->cw
== mark
->di
) {
197 /* back to the start, and no dest is found.
198 It is only possible when all dests are OVERLOADED */
200 IP_VS_ERR_RL("WRR: no destination available: "
201 "all destinations are overloaded\n");
206 IP_VS_DBG_BUF(6, "WRR: server %s:%u "
207 "activeconns %d refcnt %d weight %d\n",
208 IP_VS_DBG_ADDR(svc
->af
, &dest
->addr
), ntohs(dest
->port
),
209 atomic_read(&dest
->activeconns
),
210 atomic_read(&dest
->refcnt
),
211 atomic_read(&dest
->weight
));
214 write_unlock(&svc
->sched_lock
);
219 static struct ip_vs_scheduler ip_vs_wrr_scheduler
= {
221 .refcnt
= ATOMIC_INIT(0),
222 .module
= THIS_MODULE
,
223 .n_list
= LIST_HEAD_INIT(ip_vs_wrr_scheduler
.n_list
),
224 .init_service
= ip_vs_wrr_init_svc
,
225 .done_service
= ip_vs_wrr_done_svc
,
226 .update_service
= ip_vs_wrr_update_svc
,
227 .schedule
= ip_vs_wrr_schedule
,
230 static int __init
ip_vs_wrr_init(void)
232 return register_ip_vs_scheduler(&ip_vs_wrr_scheduler
) ;
235 static void __exit
ip_vs_wrr_cleanup(void)
237 unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler
);
240 module_init(ip_vs_wrr_init
);
241 module_exit(ip_vs_wrr_cleanup
);
242 MODULE_LICENSE("GPL");