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                   struct ip_vs_iphdr *iph)
  31 {
  32         struct ip_vs_dest *dest, *least = NULL;
  33         unsigned int loh = 0, doh;
  34
  35         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
  36
  37         /*
  38          * Simply select the server with the least number of
  39          *        (activeconns<<5) + inactconns
  40          * Except whose weight is equal to zero.
  41          * If the weight is equal to zero, it means that the server is
  42          * quiesced, the existing connections to the server still get
  43          * served, but no new connection is assigned to the server.
  44          */
  45
  46         list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
  47                 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
  48                     atomic_read(&dest->weight) == 0)
  49                         continue;
  50                 doh = ip_vs_dest_conn_overhead(dest);
  51                 if (!least || doh < loh) {
  52                         least = dest;
  53                         loh = doh;
  54                 }
  55         }
  56
  57         if (!least)
  58                 ip_vs_scheduler_err(svc, "no destination available");
  59         else
  60                 IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
  61                               "inactconns %d\n",
  62                               IP_VS_DBG_ADDR(svc->af, &least->addr),
  63                               ntohs(least->port),
  64                               atomic_read(&least->activeconns),
  65                               atomic_read(&least->inactconns));
  66
  67         return least;
  68 }
  69
  70
  71 static struct ip_vs_scheduler ip_vs_lc_scheduler = {
  72         .name =                 "lc",
  73         .refcnt =               ATOMIC_INIT(0),
  74         .module =               THIS_MODULE,
  75         .n_list =               LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
  76         .schedule =             ip_vs_lc_schedule,
  77 };
  78
  79
  80 static int __init ip_vs_lc_init(void)
  81 {
  82         return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
  83 }
  84
  85 static void __exit ip_vs_lc_cleanup(void)
  86 {
  87         unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
  88         synchronize_rcu();
  89 }
  90
  91 module_init(ip_vs_lc_init);
  92 module_exit(ip_vs_lc_cleanup);
  93 MODULE_LICENSE("GPL");