--- /dev/null
+/*
+ * 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");
Code Review / kvmfornfv.git / blobdiff