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/config.h>
  25 #include <linux/module.h>
  26 #include <linux/init.h>
  27 #include <linux/types.h>
  28 #include <linux/kernel.h>
  29 #include <linux/errno.h>
  30
  31 #include <net/ip_vs.h>
  32
  33
  34 static int
  35 ip_vs_wlc_init_svc(struct ip_vs_service *svc)
  36 {
  37         return 0;
  38 }
  39
  40
  41 static int
  42 ip_vs_wlc_done_svc(struct ip_vs_service *svc)
  43 {
  44         return 0;
  45 }
  46
  47
  48 static int
  49 ip_vs_wlc_update_svc(struct ip_vs_service *svc)
  50 {
  51         return 0;
  52 }
  53
  54
  55 static inline unsigned int
  56 ip_vs_wlc_dest_overhead(struct ip_vs_dest *dest)
  57 {
  58         /*
  59          * We think the overhead of processing active connections is 256
  60          * times higher than that of inactive connections in average. (This
  61          * 256 times might not be accurate, we will change it later) We
  62          * use the following formula to estimate the overhead now:
  63          *                dest->activeconns*256 + dest->inactconns
  64          */
  65         return (atomic_read(&dest->activeconns) << 8) +
  66                 atomic_read(&dest->inactconns);
  67 }
  68
  69
  70 /*
  71  *      Weighted Least Connection scheduling
  72  */
  73 static struct ip_vs_dest *
  74 ip_vs_wlc_schedule(struct ip_vs_service *svc, struct iphdr *iph)
  75 {
  76         register struct list_head *l, *e;
  77         struct ip_vs_dest *dest, *least;
  78         unsigned int loh, doh;
  79
  80         IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");
  81
  82         /*
  83          * We calculate the load of each dest server as follows:
  84          *                (dest overhead) / dest->weight
  85          *
  86          * Remember -- no floats in kernel mode!!!
  87          * The comparison of h1*w2 > h2*w1 is equivalent to that of
  88          *                h1/w1 > h2/w2
  89          * if every weight is larger than zero.
  90          *
  91          * The server with weight=0 is quiesced and will not receive any
  92          * new connections.
  93          */
  94
  95         l = &svc->destinations;
  96         for (e=l->next; e!=l; e=e->next) {
  97                 least = list_entry(e, struct ip_vs_dest, n_list);
  98                 if (!(least->flags & IP_VS_DEST_F_OVERLOAD) &&
  99                     atomic_read(&least->weight) > 0) {
 100                         loh = ip_vs_wlc_dest_overhead(least);
 101                         goto nextstage;
 102                 }
 103         }
 104         return NULL;
 105
 106         /*
 107          *    Find the destination with the least load.
 108          */
 109   nextstage:
 110         for (e=e->next; e!=l; e=e->next) {
 111                 dest = list_entry(e, struct ip_vs_dest, n_list);
 112
 113                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 114                         continue;
 115                 doh = ip_vs_wlc_dest_overhead(dest);
 116                 if (loh * atomic_read(&dest->weight) >
 117                     doh * atomic_read(&least->weight)) {
 118                         least = dest;
 119                         loh = doh;
 120                 }
 121         }
 122
 123         IP_VS_DBG(6, "WLC: server %u.%u.%u.%u:%u "
 124                   "activeconns %d refcnt %d weight %d overhead %d\n",
 125                   NIPQUAD(least->addr), ntohs(least->port),
 126                   atomic_read(&least->activeconns),
 127                   atomic_read(&least->refcnt),
 128                   atomic_read(&least->weight), loh);
 129
 130         return least;
 131 }
 132
 133
 134 static struct ip_vs_scheduler ip_vs_wlc_scheduler =
 135 {
 136         .name =                 "wlc",
 137         .refcnt =               ATOMIC_INIT(0),
 138         .module =               THIS_MODULE,
 139         .init_service =         ip_vs_wlc_init_svc,
 140         .done_service =         ip_vs_wlc_done_svc,
 141         .update_service =       ip_vs_wlc_update_svc,
 142         .schedule =             ip_vs_wlc_schedule,
 143 };
 144
 145
 146 static int __init ip_vs_wlc_init(void)
 147 {
 148         INIT_LIST_HEAD(&ip_vs_wlc_scheduler.n_list);
 149         return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 150 }
 151
 152 static void __exit ip_vs_wlc_cleanup(void)
 153 {
 154         unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 155 }
 156
 157 module_init(ip_vs_wlc_init);
 158 module_exit(ip_vs_wlc_cleanup);
 159 MODULE_LICENSE("GPL");