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/*
* IPVS: Weighted Round-Robin Scheduling module
*
* Version: $Id: ip_vs_wrr.c,v 1.12 2002/09/15 08:14:08 wensong Exp $
*
* Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Changes:
* Wensong Zhang : changed the ip_vs_wrr_schedule to return dest
* Wensong Zhang : changed some comestics things for debugging
* Wensong Zhang : changed for the d-linked destination list
* Wensong Zhang : added the ip_vs_wrr_update_svc
* Julian Anastasov : fixed the bug of returning destination
* with weight 0 when all weights are zero
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <net/ip_vs.h>
/*
* current destination pointer for weighted round-robin scheduling
*/
struct ip_vs_wrr_mark {
struct list_head *cl; /* current list head */
int cw; /* current weight */
int mw; /* maximum weight */
int di; /* decreasing interval */
};
/*
* Get the gcd of server weights
*/
static int gcd(int a, int b)
{
int c;
while ((c = a % b)) {
a = b;
b = c;
}
return b;
}
static int ip_vs_wrr_gcd_weight(struct ip_vs_service *svc)
{
struct ip_vs_dest *dest;
int weight;
int g = 0;
list_for_each_entry(dest, &svc->destinations, n_list) {
weight = atomic_read(&dest->weight);
if (weight > 0) {
if (g > 0)
g = gcd(weight, g);
else
g = weight;
}
}
return g ? g : 1;
}
/*
* Get the maximum weight of the service destinations.
*/
static int ip_vs_wrr_max_weight(struct ip_vs_service *svc)
{
struct ip_vs_dest *dest;
int weight = 0;
list_for_each_entry(dest, &svc->destinations, n_list) {
if (atomic_read(&dest->weight) > weight)
weight = atomic_read(&dest->weight);
}
return weight;
}
static int ip_vs_wrr_init_svc(struct ip_vs_service *svc)
{
struct ip_vs_wrr_mark *mark;
/*
* Allocate the mark variable for WRR scheduling
*/
mark = kmalloc(sizeof(struct ip_vs_wrr_mark), GFP_ATOMIC);
if (mark == NULL) {
IP_VS_ERR("ip_vs_wrr_init_svc(): no memory\n");
return -ENOMEM;
}
mark->cl = &svc->destinations;
mark->cw = 0;
mark->mw = ip_vs_wrr_max_weight(svc);
mark->di = ip_vs_wrr_gcd_weight(svc);
svc->sched_data = mark;
return 0;
}
static int ip_vs_wrr_done_svc(struct ip_vs_service *svc)
{
/*
* Release the mark variable
*/
kfree(svc->sched_data);
return 0;
}
static int ip_vs_wrr_update_svc(struct ip_vs_service *svc)
{
struct ip_vs_wrr_mark *mark = svc->sched_data;
mark->cl = &svc->destinations;
mark->mw = ip_vs_wrr_max_weight(svc);
mark->di = ip_vs_wrr_gcd_weight(svc);
if (mark->cw > mark->mw)
mark->cw = 0;
return 0;
}
/*
* Weighted Round-Robin Scheduling
*/
static struct ip_vs_dest *
ip_vs_wrr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
struct ip_vs_dest *dest;
struct ip_vs_wrr_mark *mark = svc->sched_data;
struct list_head *p;
IP_VS_DBG(6, "ip_vs_wrr_schedule(): Scheduling...\n");
/*
* This loop will always terminate, because mark->cw in (0, max_weight]
* and at least one server has its weight equal to max_weight.
*/
write_lock(&svc->sched_lock);
p = mark->cl;
while (1) {
if (mark->cl == &svc->destinations) {
/* it is at the head of the destination list */
if (mark->cl == mark->cl->next) {
/* no dest entry */
dest = NULL;
goto out;
}
mark->cl = svc->destinations.next;
mark->cw -= mark->di;
if (mark->cw <= 0) {
mark->cw = mark->mw;
/*
* Still zero, which means no available servers.
*/
if (mark->cw == 0) {
mark->cl = &svc->destinations;
IP_VS_INFO("ip_vs_wrr_schedule(): "
"no available servers\n");
dest = NULL;
goto out;
}
}
} else
mark->cl = mark->cl->next;
if (mark->cl != &svc->destinations) {
/* not at the head of the list */
dest = list_entry(mark->cl, struct ip_vs_dest, n_list);
if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
atomic_read(&dest->weight) >= mark->cw) {
/* got it */
break;
}
}
if (mark->cl == p && mark->cw == mark->di) {
/* back to the start, and no dest is found.
It is only possible when all dests are OVERLOADED */
dest = NULL;
goto out;
}
}
IP_VS_DBG(6, "WRR: server %u.%u.%u.%u:%u "
"activeconns %d refcnt %d weight %d\n",
NIPQUAD(dest->addr), ntohs(dest->port),
atomic_read(&dest->activeconns),
atomic_read(&dest->refcnt),
atomic_read(&dest->weight));
out:
write_unlock(&svc->sched_lock);
return dest;
}
static struct ip_vs_scheduler ip_vs_wrr_scheduler = {
.name = "wrr",
.refcnt = ATOMIC_INIT(0),
.module = THIS_MODULE,
.init_service = ip_vs_wrr_init_svc,
.done_service = ip_vs_wrr_done_svc,
.update_service = ip_vs_wrr_update_svc,
.schedule = ip_vs_wrr_schedule,
};
static int __init ip_vs_wrr_init(void)
{
INIT_LIST_HEAD(&ip_vs_wrr_scheduler.n_list);
return register_ip_vs_scheduler(&ip_vs_wrr_scheduler) ;
}
static void __exit ip_vs_wrr_cleanup(void)
{
unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler);
}
module_init(ip_vs_wrr_init);
module_exit(ip_vs_wrr_cleanup);
MODULE_LICENSE("GPL");
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