net/ipv4/ipvs/ip_vs_lc.c

   1 /*
   2  * IPVS:        Least-Connection Scheduling module
   3  *
   4  * Version:     $Id: ip_vs_lc.c,v 1.10 2003/04/18 09:03:16 wensong Exp $
   5  *
   6  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   7  *
   8  *              This program is free software; you can redistribute it and/or
   9  *              modify it under the terms of the GNU General Public License
  10  *              as published by the Free Software Foundation; either version
  11  *              2 of the License, or (at your option) any later version.
  12  *
  13  * Changes:
  14  *     Wensong Zhang            :     added the ip_vs_lc_update_svc
  15  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
  16  *
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/kernel.h>
  21
  22 #include <net/ip_vs.h>
  23
  24
  25 static int ip_vs_lc_init_svc(struct ip_vs_service *svc)
  26 {
  27         return 0;
  28 }
  29
  30
  31 static int ip_vs_lc_done_svc(struct ip_vs_service *svc)
  32 {
  33         return 0;
  34 }
  35
  36
  37 static int ip_vs_lc_update_svc(struct ip_vs_service *svc)
  38 {
  39         return 0;
  40 }
  41
  42
  43 static inline unsigned int
  44 ip_vs_lc_dest_overhead(struct ip_vs_dest *dest)
  45 {
  46         /*
  47          * We think the overhead of processing active connections is 256
  48          * times higher than that of inactive connections in average. (This
  49          * 256 times might not be accurate, we will change it later) We
  50          * use the following formula to estimate the overhead now:
  51          *                dest->activeconns*256 + dest->inactconns
  52          */
  53         return (atomic_read(&dest->activeconns) << 8) +
  54                 atomic_read(&dest->inactconns);
  55 }
  56
  57
  58 /*
  59  *      Least Connection scheduling
  60  */
  61 static struct ip_vs_dest *
  62 ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  63 {
  64         struct ip_vs_dest *dest, *least = NULL;
  65         unsigned int loh = 0, doh;
  66
  67         IP_VS_DBG(6, "ip_vs_lc_schedule(): Scheduling...\n");
  68
  69         /*
  70          * Simply select the server with the least number of
  71          *        (activeconns<<5) + inactconns
  72          * Except whose weight is equal to zero.
  73          * If the weight is equal to zero, it means that the server is
  74          * quiesced, the existing connections to the server still get
  75          * served, but no new connection is assigned to the server.
  76          */
  77
  78         list_for_each_entry(dest, &svc->destinations, n_list) {
  79                 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
  80                     atomic_read(&dest->weight) == 0)
  81                         continue;
  82                 doh = ip_vs_lc_dest_overhead(dest);
  83                 if (!least || doh < loh) {
  84                         least = dest;
  85                         loh = doh;
  86                 }
  87         }
  88
  89         if (least)
  90         IP_VS_DBG(6, "LC: server %u.%u.%u.%u:%u activeconns %d inactconns %d\n",
  91                   NIPQUAD(least->addr), ntohs(least->port),
  92                   atomic_read(&least->activeconns),
  93                   atomic_read(&least->inactconns));
  94
  95         return least;
  96 }
  97
  98
  99 static struct ip_vs_scheduler ip_vs_lc_scheduler = {
 100         .name =                 "lc",
 101         .refcnt =               ATOMIC_INIT(0),
 102         .module =               THIS_MODULE,
 103         .init_service =         ip_vs_lc_init_svc,
 104         .done_service =         ip_vs_lc_done_svc,
 105         .update_service =       ip_vs_lc_update_svc,
 106         .schedule =             ip_vs_lc_schedule,
 107 };
 108
 109
 110 static int __init ip_vs_lc_init(void)
 111 {
 112         INIT_LIST_HEAD(&ip_vs_lc_scheduler.n_list);
 113         return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
 114 }
 115
 116 static void __exit ip_vs_lc_cleanup(void)
 117 {
 118         unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
 119 }
 120
 121 module_init(ip_vs_lc_init);
 122 module_exit(ip_vs_lc_cleanup);
 123 MODULE_LICENSE("GPL");