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   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 inline unsigned int
  29 ip_vs_wlc_dest_overhead(struct ip_vs_dest *dest)
  30 {
  31         /*
  32          * We think the overhead of processing active connections is 256
  33          * times higher than that of inactive connections in average. (This
  34          * 256 times might not be accurate, we will change it later) We
  35          * use the following formula to estimate the overhead now:
  36          *                dest->activeconns*256 + dest->inactconns
  37          */
  38         return (atomic_read(&dest->activeconns) << 8) +
  39                 atomic_read(&dest->inactconns);
  40 }
  41
  42
  43 /*
  44  *      Weighted Least Connection scheduling
  45  */
  46 static struct ip_vs_dest *
  47 ip_vs_wlc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  48 {
  49         struct ip_vs_dest *dest, *least;
  50         unsigned int loh, doh;
  51
  52         IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");
  53
  54         /*
  55          * We calculate the load of each dest server as follows:
  56          *                (dest overhead) / dest->weight
  57          *
  58          * Remember -- no floats in kernel mode!!!
  59          * The comparison of h1*w2 > h2*w1 is equivalent to that of
  60          *                h1/w1 > h2/w2
  61          * if every weight is larger than zero.
  62          *
  63          * The server with weight=0 is quiesced and will not receive any
  64          * new connections.
  65          */
  66
  67         list_for_each_entry(dest, &svc->destinations, n_list) {
  68                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  69                     atomic_read(&dest->weight) > 0) {
  70                         least = dest;
  71                         loh = ip_vs_wlc_dest_overhead(least);
  72                         goto nextstage;
  73                 }
  74         }
  75         IP_VS_ERR_RL("WLC: no destination available\n");
  76         return NULL;
  77
  78         /*
  79          *    Find the destination with the least load.
  80          */
  81   nextstage:
  82         list_for_each_entry_continue(dest, &svc->destinations, n_list) {
  83                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
  84                         continue;
  85                 doh = ip_vs_wlc_dest_overhead(dest);
  86                 if (loh * atomic_read(&dest->weight) >
  87                     doh * atomic_read(&least->weight)) {
  88                         least = dest;
  89                         loh = doh;
  90                 }
  91         }
  92
  93         IP_VS_DBG_BUF(6, "WLC: server %s:%u "
  94                       "activeconns %d refcnt %d weight %d overhead %d\n",
  95                       IP_VS_DBG_ADDR(svc->af, &least->addr), ntohs(least->port),
  96                       atomic_read(&least->activeconns),
  97                       atomic_read(&least->refcnt),
  98                       atomic_read(&least->weight), loh);
  99
 100         return least;
 101 }
 102
 103
 104 static struct ip_vs_scheduler ip_vs_wlc_scheduler =
 105 {
 106         .name =                 "wlc",
 107         .refcnt =               ATOMIC_INIT(0),
 108         .module =               THIS_MODULE,
 109         .n_list =               LIST_HEAD_INIT(ip_vs_wlc_scheduler.n_list),
 110         .schedule =             ip_vs_wlc_schedule,
 111 };
 112
 113
 114 static int __init ip_vs_wlc_init(void)
 115 {
 116         return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 117 }
 118
 119 static void __exit ip_vs_wlc_cleanup(void)
 120 {
 121         unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 122 }
 123
 124 module_init(ip_vs_wlc_init);
 125 module_exit(ip_vs_wlc_cleanup);
 126 MODULE_LICENSE("GPL");