net/ipv4/ipvs/ip_vs_wlc.c

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