ip_vs_lc.c

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/*
 * IPVS:        Least-Connection Scheduling module
 *
 * Authors:     Wensong Zhang <[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            :     added the ip_vs_lc_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>

/*
 *  Least Connection scheduling
 */
static struct ip_vs_dest *
ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
    struct ip_vs_dest *dest, *least = NULL;
    unsigned int loh = 0, doh;

    IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);

    /*
     * Simply select the server with the least number of
     *        (activeconns<<5) + inactconns
     * Except whose weight is equal to zero.
     * If the weight is equal to zero, it means that the server is
     * quiesced, the existing connections to the server still get
     * served, but no new connection is assigned to the server.
     */

    list_for_each_entry(dest, &svc->destinations, n_list) {
        if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
            atomic_read(&dest->weight) == 0)
            continue;
        doh = ip_vs_dest_conn_overhead(dest);
        if (!least || doh < loh) {
            least = dest;
            loh = doh;
        }
    }

    if (!least)
        ip_vs_scheduler_err(svc, "no destination available");
    else
        IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
                  "inactconns %d\n",
                  IP_VS_DBG_ADDR(svc->af, &least->addr),
                  ntohs(least->port),
                  atomic_read(&least->activeconns),
                  atomic_read(&least->inactconns));

    return least;
}


static struct ip_vs_scheduler ip_vs_lc_scheduler = {
    .name =         "lc",
    .refcnt =       ATOMIC_INIT(0),
    .module =       THIS_MODULE,
    .n_list =       LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
    .schedule =     ip_vs_lc_schedule,
};


static int __init ip_vs_lc_init(void)
{
    return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
}

static void __exit ip_vs_lc_cleanup(void)
{
    unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
}

module_init(ip_vs_lc_init);
module_exit(ip_vs_lc_cleanup);
MODULE_LICENSE("GPL");