/* * 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");