ip_vs_wlc.c

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/*
 * IPVS:        Weighted Least-Connection Scheduling module
 *
 * Authors:     Wensong Zhang <[email protected]>
 *              Peter Kese <[email protected]>
 *
 *              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_wlc_schedule to return dest
 *     Wensong Zhang            :     changed to use the inactconns in scheduling
 *     Wensong Zhang            :     changed some comestics things for debugging
 *     Wensong Zhang            :     changed for the d-linked destination list
 *     Wensong Zhang            :     added the ip_vs_wlc_update_svc
 *     Wensong Zhang            :     added any dest with weight=0 is quiesced
 *
 */

#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>

#include <net/ip_vs.h>

/*
 *  Weighted Least Connection scheduling
 */
static struct ip_vs_dest *
ip_vs_wlc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
    struct ip_vs_dest *dest, *least;
    unsigned int loh, doh;

    IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");

    /*
     * We calculate the load of each dest server as follows:
     *        (dest overhead) / dest->weight
     *
     * Remember -- no floats in kernel mode!!!
     * The comparison of h1*w2 > h2*w1 is equivalent to that of
     *        h1/w1 > h2/w2
     * if every weight is larger than zero.
     *
     * The server with weight=0 is quiesced and will not receive any
     * new connections.
     */

    list_for_each_entry(dest, &svc->destinations, n_list) {
        if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
            atomic_read(&dest->weight) > 0) {
            least = dest;
            loh = ip_vs_dest_conn_overhead(least);
            goto nextstage;
        }
    }
    ip_vs_scheduler_err(svc, "no destination available");
    return NULL;

    /*
     *    Find the destination with the least load.
     */
  nextstage:
    list_for_each_entry_continue(dest, &svc->destinations, n_list) {
        if (dest->flags & IP_VS_DEST_F_OVERLOAD)
            continue;
        doh = ip_vs_dest_conn_overhead(dest);
        if (loh * atomic_read(&dest->weight) >
            doh * atomic_read(&least->weight)) {
            least = dest;
            loh = doh;
        }
    }

    IP_VS_DBG_BUF(6, "WLC: server %s:%u "
              "activeconns %d refcnt %d weight %d overhead %d\n",
              IP_VS_DBG_ADDR(svc->af, &least->addr), ntohs(least->port),
              atomic_read(&least->activeconns),
              atomic_read(&least->refcnt),
              atomic_read(&least->weight), loh);

    return least;
}


static struct ip_vs_scheduler ip_vs_wlc_scheduler =
{
    .name =         "wlc",
    .refcnt =       ATOMIC_INIT(0),
    .module =       THIS_MODULE,
    .n_list =       LIST_HEAD_INIT(ip_vs_wlc_scheduler.n_list),
    .schedule =     ip_vs_wlc_schedule,
};


static int __init ip_vs_wlc_init(void)
{
    return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
}

static void __exit ip_vs_wlc_cleanup(void)
{
    unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
}

module_init(ip_vs_wlc_init);
module_exit(ip_vs_wlc_cleanup);
MODULE_LICENSE("GPL");