net/netfilter/ipvs/ip_vs_lc.c

   1 /*
   2  * IPVS:        Least-Connection Scheduling module
   3  *
   4  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   5  *
   6  *              This program is free software; you can redistribute it and/or
   7  *              modify it under the terms of the GNU General Public License
   8  *              as published by the Free Software Foundation; either version
   9  *              2 of the License, or (at your option) any later version.
  10  *
  11  * Changes:
  12  *     Wensong Zhang            :     added the ip_vs_lc_update_svc
  13  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
  14  *
  15  */
  16
  17 #define KMSG_COMPONENT "IPVS"
  18 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  19
  20 #include <linux/module.h>
  21 #include <linux/kernel.h>
  22
  23 #include <net/ip_vs.h>
  24
  25 /*
  26  *      Least Connection scheduling
  27  */
  28 static struct ip_vs_dest *
  29 ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  30 {
  31         struct ip_vs_dest *dest, *least = NULL;
  32         unsigned int loh = 0, doh;
  33
  34         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
  35
  36         /*
  37          * Simply select the server with the least number of
  38          *        (activeconns<<5) + inactconns
  39          * Except whose weight is equal to zero.
  40          * If the weight is equal to zero, it means that the server is
  41          * quiesced, the existing connections to the server still get
  42          * served, but no new connection is assigned to the server.
  43          */
  44
  45         list_for_each_entry(dest, &svc->destinations, n_list) {
  46                 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
  47                     atomic_read(&dest->weight) == 0)
  48                         continue;
  49                 doh = ip_vs_dest_conn_overhead(dest);
  50                 if (!least || doh < loh) {
  51                         least = dest;
  52                         loh = doh;
  53                 }
  54         }
  55
  56         if (!least)
  57                 ip_vs_scheduler_err(svc, "no destination available");
  58         else
  59                 IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
  60                               "inactconns %d\n",
  61                               IP_VS_DBG_ADDR(svc->af, &least->addr),
  62                               ntohs(least->port),
  63                               atomic_read(&least->activeconns),
  64                               atomic_read(&least->inactconns));
  65
  66         return least;
  67 }
  68
  69
  70 static struct ip_vs_scheduler ip_vs_lc_scheduler = {
  71         .name =                 "lc",
  72         .refcnt =               ATOMIC_INIT(0),
  73         .module =               THIS_MODULE,
  74         .n_list =               LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
  75         .schedule =             ip_vs_lc_schedule,
  76 };
  77
  78
  79 static int __init ip_vs_lc_init(void)
  80 {
  81         return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
  82 }
  83
  84 static void __exit ip_vs_lc_cleanup(void)
  85 {
  86         unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
  87 }
  88
  89 module_init(ip_vs_lc_init);
  90 module_exit(ip_vs_lc_cleanup);
  91 MODULE_LICENSE("GPL");