net/ipv4/ipvs/ip_vs_wlc.c

   1 /*
   2  * IPVS:        Weighted Least-Connection Scheduling module
   3  *
   4  * Version:     $Id: ip_vs_wlc.c,v 1.13 2003/04/18 09:03:16 wensong Exp $
   5  *
   6  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   7  *              Peter Kese <peter.kese@ijs.si>
   8  *
   9  *              This program is free software; you can redistribute it and/or
  10  *              modify it under the terms of the GNU General Public License
  11  *              as published by the Free Software Foundation; either version
  12  *              2 of the License, or (at your option) any later version.
  13  *
  14  * Changes:
  15  *     Wensong Zhang            :     changed the ip_vs_wlc_schedule to return dest
  16  *     Wensong Zhang            :     changed to use the inactconns in scheduling
  17  *     Wensong Zhang            :     changed some comestics things for debugging
  18  *     Wensong Zhang            :     changed for the d-linked destination list
  19  *     Wensong Zhang            :     added the ip_vs_wlc_update_svc
  20  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
  21  *
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/kernel.h>
  26
  27 #include <net/ip_vs.h>
  28
  29
  30 static int
  31 ip_vs_wlc_init_svc(struct ip_vs_service *svc)
  32 {
  33         return 0;
  34 }
  35
  36
  37 static int
  38 ip_vs_wlc_done_svc(struct ip_vs_service *svc)
  39 {
  40         return 0;
  41 }
  42
  43
  44 static int
  45 ip_vs_wlc_update_svc(struct ip_vs_service *svc)
  46 {
  47         return 0;
  48 }
  49
  50
  51 static inline unsigned int
  52 ip_vs_wlc_dest_overhead(struct ip_vs_dest *dest)
  53 {
  54         /*
  55          * We think the overhead of processing active connections is 256
  56          * times higher than that of inactive connections in average. (This
  57          * 256 times might not be accurate, we will change it later) We
  58          * use the following formula to estimate the overhead now:
  59          *                dest->activeconns*256 + dest->inactconns
  60          */
  61         return (atomic_read(&dest->activeconns) << 8) +
  62                 atomic_read(&dest->inactconns);
  63 }
  64
  65
  66 /*
  67  *      Weighted Least Connection scheduling
  68  */
  69 static struct ip_vs_dest *
  70 ip_vs_wlc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  71 {
  72         struct ip_vs_dest *dest, *least;
  73         unsigned int loh, doh;
  74
  75         IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");
  76
  77         /*
  78          * We calculate the load of each dest server as follows:
  79          *                (dest overhead) / dest->weight
  80          *
  81          * Remember -- no floats in kernel mode!!!
  82          * The comparison of h1*w2 > h2*w1 is equivalent to that of
  83          *                h1/w1 > h2/w2
  84          * if every weight is larger than zero.
  85          *
  86          * The server with weight=0 is quiesced and will not receive any
  87          * new connections.
  88          */
  89
  90         list_for_each_entry(dest, &svc->destinations, n_list) {
  91                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  92                     atomic_read(&dest->weight) > 0) {
  93                         least = dest;
  94                         loh = ip_vs_wlc_dest_overhead(least);
  95                         goto nextstage;
  96                 }
  97         }
  98         return NULL;
  99
 100         /*
 101          *    Find the destination with the least load.
 102          */
 103   nextstage:
 104         list_for_each_entry_continue(dest, &svc->destinations, n_list) {
 105                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 106                         continue;
 107                 doh = ip_vs_wlc_dest_overhead(dest);
 108                 if (loh * atomic_read(&dest->weight) >
 109                     doh * atomic_read(&least->weight)) {
 110                         least = dest;
 111                         loh = doh;
 112                 }
 113         }
 114
 115         IP_VS_DBG(6, "WLC: server %u.%u.%u.%u:%u "
 116                   "activeconns %d refcnt %d weight %d overhead %d\n",
 117                   NIPQUAD(least->addr), ntohs(least->port),
 118                   atomic_read(&least->activeconns),
 119                   atomic_read(&least->refcnt),
 120                   atomic_read(&least->weight), loh);
 121
 122         return least;
 123 }
 124
 125
 126 static struct ip_vs_scheduler ip_vs_wlc_scheduler =
 127 {
 128         .name =                 "wlc",
 129         .refcnt =               ATOMIC_INIT(0),
 130         .module =               THIS_MODULE,
 131         .init_service =         ip_vs_wlc_init_svc,
 132         .done_service =         ip_vs_wlc_done_svc,
 133         .update_service =       ip_vs_wlc_update_svc,
 134         .schedule =             ip_vs_wlc_schedule,
 135 };
 136
 137
 138 static int __init ip_vs_wlc_init(void)
 139 {
 140         INIT_LIST_HEAD(&ip_vs_wlc_scheduler.n_list);
 141         return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 142 }
 143
 144 static void __exit ip_vs_wlc_cleanup(void)
 145 {
 146         unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 147 }
 148
 149 module_init(ip_vs_wlc_init);
 150 module_exit(ip_vs_wlc_cleanup);
 151 MODULE_LICENSE("GPL");