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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 #define KMSG_COMPONENT "IPVS"
  23 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  24
  25 #include <linux/module.h>
  26 #include <linux/kernel.h>
  27
  28 #include <net/ip_vs.h>
  29
  30
  31 static inline unsigned int
  32 ip_vs_wlc_dest_overhead(struct ip_vs_dest *dest)
  33 {
  34         /*
  35          * We think the overhead of processing active connections is 256
  36          * times higher than that of inactive connections in average. (This
  37          * 256 times might not be accurate, we will change it later) We
  38          * use the following formula to estimate the overhead now:
  39          *                dest->activeconns*256 + dest->inactconns
  40          */
  41         return (atomic_read(&dest->activeconns) << 8) +
  42                 atomic_read(&dest->inactconns);
  43 }
  44
  45
  46 /*
  47  *      Weighted Least Connection scheduling
  48  */
  49 static struct ip_vs_dest *
  50 ip_vs_wlc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  51 {
  52         struct ip_vs_dest *dest, *least;
  53         unsigned int loh, doh;
  54
  55         IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");
  56
  57         /*
  58          * We calculate the load of each dest server as follows:
  59          *                (dest overhead) / dest->weight
  60          *
  61          * Remember -- no floats in kernel mode!!!
  62          * The comparison of h1*w2 > h2*w1 is equivalent to that of
  63          *                h1/w1 > h2/w2
  64          * if every weight is larger than zero.
  65          *
  66          * The server with weight=0 is quiesced and will not receive any
  67          * new connections.
  68          */
  69
  70         list_for_each_entry(dest, &svc->destinations, n_list) {
  71                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  72                     atomic_read(&dest->weight) > 0) {
  73                         least = dest;
  74                         loh = ip_vs_wlc_dest_overhead(least);
  75                         goto nextstage;
  76                 }
  77         }
  78         IP_VS_ERR_RL("WLC: no destination available\n");
  79         return NULL;
  80
  81         /*
  82          *    Find the destination with the least load.
  83          */
  84   nextstage:
  85         list_for_each_entry_continue(dest, &svc->destinations, n_list) {
  86                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
  87                         continue;
  88                 doh = ip_vs_wlc_dest_overhead(dest);
  89                 if (loh * atomic_read(&dest->weight) >
  90                     doh * atomic_read(&least->weight)) {
  91                         least = dest;
  92                         loh = doh;
  93                 }
  94         }
  95
  96         IP_VS_DBG_BUF(6, "WLC: server %s:%u "
  97                       "activeconns %d refcnt %d weight %d overhead %d\n",
  98                       IP_VS_DBG_ADDR(svc->af, &least->addr), ntohs(least->port),
  99                       atomic_read(&least->activeconns),
 100                       atomic_read(&least->refcnt),
 101                       atomic_read(&least->weight), loh);
 102
 103         return least;
 104 }
 105
 106
 107 static struct ip_vs_scheduler ip_vs_wlc_scheduler =
 108 {
 109         .name =                 "wlc",
 110         .refcnt =               ATOMIC_INIT(0),
 111         .module =               THIS_MODULE,
 112         .n_list =               LIST_HEAD_INIT(ip_vs_wlc_scheduler.n_list),
 113         .schedule =             ip_vs_wlc_schedule,
 114 };
 115
 116
 117 static int __init ip_vs_wlc_init(void)
 118 {
 119         return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 120 }
 121
 122 static void __exit ip_vs_wlc_cleanup(void)
 123 {
 124         unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 125 }
 126
 127 module_init(ip_vs_wlc_init);
 128 module_exit(ip_vs_wlc_cleanup);
 129 MODULE_LICENSE("GPL");