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- /*
- * IPVS: Weighted Round-Robin Scheduling module
- *
- * 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
- *
- */
- #define KMSG_COMPONENT "IPVS"
- #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
- #include <linux/module.h>
- #include <linux/kernel.h>
- #include <linux/slab.h>
- #include <linux/net.h>
- #include <linux/gcd.h>
- #include <net/ip_vs.h>
- /* The WRR algorithm depends on some caclulations:
- * - mw: maximum weight
- * - di: weight step, greatest common divisor from all weights
- * - cw: current required weight
- * As result, all weights are in the [di..mw] range with a step=di.
- *
- * First, we start with cw = mw and select dests with weight >= cw.
- * Then cw is reduced with di and all dests are checked again.
- * Last pass should be with cw = di. We have mw/di passes in total:
- *
- * pass 1: cw = max weight
- * pass 2: cw = max weight - di
- * pass 3: cw = max weight - 2 * di
- * ...
- * last pass: cw = di
- *
- * Weights are supposed to be >= di but we run in parallel with
- * weight changes, it is possible some dest weight to be reduced
- * below di, bad if it is the only available dest.
- *
- * So, we modify how mw is calculated, now it is reduced with (di - 1),
- * so that last cw is 1 to catch such dests with weight below di:
- * pass 1: cw = max weight - (di - 1)
- * pass 2: cw = max weight - di - (di - 1)
- * pass 3: cw = max weight - 2 * di - (di - 1)
- * ...
- * last pass: cw = 1
- *
- */
- /*
- * current destination pointer for weighted round-robin scheduling
- */
- struct ip_vs_wrr_mark {
- struct ip_vs_dest *cl; /* current dest or head */
- int cw; /* current weight */
- int mw; /* maximum weight */
- int di; /* decreasing interval */
- struct rcu_head rcu_head;
- };
- 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 new_weight, weight = 0;
- list_for_each_entry(dest, &svc->destinations, n_list) {
- new_weight = atomic_read(&dest->weight);
- if (new_weight > weight)
- weight = new_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_KERNEL);
- if (mark == NULL)
- return -ENOMEM;
- mark->cl = list_entry(&svc->destinations, struct ip_vs_dest, n_list);
- mark->di = ip_vs_wrr_gcd_weight(svc);
- mark->mw = ip_vs_wrr_max_weight(svc) - (mark->di - 1);
- mark->cw = mark->mw;
- svc->sched_data = mark;
- return 0;
- }
- static void ip_vs_wrr_done_svc(struct ip_vs_service *svc)
- {
- struct ip_vs_wrr_mark *mark = svc->sched_data;
- /*
- * Release the mark variable
- */
- kfree_rcu(mark, rcu_head);
- }
- static int ip_vs_wrr_dest_changed(struct ip_vs_service *svc,
- struct ip_vs_dest *dest)
- {
- struct ip_vs_wrr_mark *mark = svc->sched_data;
- spin_lock_bh(&svc->sched_lock);
- mark->cl = list_entry(&svc->destinations, struct ip_vs_dest, n_list);
- mark->di = ip_vs_wrr_gcd_weight(svc);
- mark->mw = ip_vs_wrr_max_weight(svc) - (mark->di - 1);
- if (mark->cw > mark->mw || !mark->cw)
- mark->cw = mark->mw;
- else if (mark->di > 1)
- mark->cw = (mark->cw / mark->di) * mark->di + 1;
- spin_unlock_bh(&svc->sched_lock);
- 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_iphdr *iph)
- {
- struct ip_vs_dest *dest, *last, *stop = NULL;
- struct ip_vs_wrr_mark *mark = svc->sched_data;
- bool last_pass = false, restarted = false;
- IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
- spin_lock_bh(&svc->sched_lock);
- dest = mark->cl;
- /* No available dests? */
- if (mark->mw == 0)
- goto err_noavail;
- last = dest;
- /* Stop only after all dests were checked for weight >= 1 (last pass) */
- while (1) {
- list_for_each_entry_continue_rcu(dest,
- &svc->destinations,
- n_list) {
- if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
- atomic_read(&dest->weight) >= mark->cw)
- goto found;
- if (dest == stop)
- goto err_over;
- }
- mark->cw -= mark->di;
- if (mark->cw <= 0) {
- mark->cw = mark->mw;
- /* Stop if we tried last pass from first dest:
- * 1. last_pass: we started checks when cw > di but
- * then all dests were checked for w >= 1
- * 2. last was head: the first and only traversal
- * was for weight >= 1, for all dests.
- */
- if (last_pass ||
- &last->n_list == &svc->destinations)
- goto err_over;
- restarted = true;
- }
- last_pass = mark->cw <= mark->di;
- if (last_pass && restarted &&
- &last->n_list != &svc->destinations) {
- /* First traversal was for w >= 1 but only
- * for dests after 'last', now do the same
- * for all dests up to 'last'.
- */
- stop = last;
- }
- }
- found:
- IP_VS_DBG_BUF(6, "WRR: server %s:%u "
- "activeconns %d refcnt %d weight %d\n",
- IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
- atomic_read(&dest->activeconns),
- atomic_read(&dest->refcnt),
- atomic_read(&dest->weight));
- mark->cl = dest;
- out:
- spin_unlock_bh(&svc->sched_lock);
- return dest;
- err_noavail:
- mark->cl = dest;
- dest = NULL;
- ip_vs_scheduler_err(svc, "no destination available");
- goto out;
- err_over:
- mark->cl = dest;
- dest = NULL;
- ip_vs_scheduler_err(svc, "no destination available: "
- "all destinations are overloaded");
- goto out;
- }
- static struct ip_vs_scheduler ip_vs_wrr_scheduler = {
- .name = "wrr",
- .refcnt = ATOMIC_INIT(0),
- .module = THIS_MODULE,
- .n_list = LIST_HEAD_INIT(ip_vs_wrr_scheduler.n_list),
- .init_service = ip_vs_wrr_init_svc,
- .done_service = ip_vs_wrr_done_svc,
- .add_dest = ip_vs_wrr_dest_changed,
- .del_dest = ip_vs_wrr_dest_changed,
- .upd_dest = ip_vs_wrr_dest_changed,
- .schedule = ip_vs_wrr_schedule,
- };
- static int __init ip_vs_wrr_init(void)
- {
- 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);
- synchronize_rcu();
- }
- module_init(ip_vs_wrr_init);
- module_exit(ip_vs_wrr_cleanup);
- MODULE_LICENSE("GPL");
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