net/netfilter/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 #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  *      Weighted Least Connection scheduling
  32  */
  33 static struct ip_vs_dest *
  34 ip_vs_wlc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
  35                    struct ip_vs_iphdr *iph)
  36 {
  37         struct ip_vs_dest *dest, *least;
  38         int loh, doh;
  39
  40         IP_VS_DBG(6, "ip_vs_wlc_schedule(): Scheduling...\n");
  41
  42         /*
  43          * We calculate the load of each dest server as follows:
  44          *                (dest overhead) / dest->weight
  45          *
  46          * Remember -- no floats in kernel mode!!!
  47          * The comparison of h1*w2 > h2*w1 is equivalent to that of
  48          *                h1/w1 > h2/w2
  49          * if every weight is larger than zero.
  50          *
  51          * The server with weight=0 is quiesced and will not receive any
  52          * new connections.
  53          */
  54
  55         list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
  56                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  57                     atomic_read(&dest->weight) > 0) {
  58                         least = dest;
  59                         loh = ip_vs_dest_conn_overhead(least);
  60                         goto nextstage;
  61                 }
  62         }
  63         ip_vs_scheduler_err(svc, "no destination available");
  64         return NULL;
  65
  66         /*
  67          *    Find the destination with the least load.
  68          */
  69   nextstage:
  70         list_for_each_entry_continue_rcu(dest, &svc->destinations, n_list) {
  71                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
  72                         continue;
  73                 doh = ip_vs_dest_conn_overhead(dest);
  74                 if ((__s64)loh * atomic_read(&dest->weight) >
  75                     (__s64)doh * atomic_read(&least->weight)) {
  76                         least = dest;
  77                         loh = doh;
  78                 }
  79         }
  80
  81         IP_VS_DBG_BUF(6, "WLC: server %s:%u "
  82                       "activeconns %d refcnt %d weight %d overhead %d\n",
  83                       IP_VS_DBG_ADDR(svc->af, &least->addr), ntohs(least->port),
  84                       atomic_read(&least->activeconns),
  85                       atomic_read(&least->refcnt),
  86                       atomic_read(&least->weight), loh);
  87
  88         return least;
  89 }
  90
  91
  92 static struct ip_vs_scheduler ip_vs_wlc_scheduler =
  93 {
  94         .name =                 "wlc",
  95         .refcnt =               ATOMIC_INIT(0),
  96         .module =               THIS_MODULE,
  97         .n_list =               LIST_HEAD_INIT(ip_vs_wlc_scheduler.n_list),
  98         .schedule =             ip_vs_wlc_schedule,
  99 };
 100
 101
 102 static int __init ip_vs_wlc_init(void)
 103 {
 104         return register_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 105 }
 106
 107 static void __exit ip_vs_wlc_cleanup(void)
 108 {
 109         unregister_ip_vs_scheduler(&ip_vs_wlc_scheduler);
 110         synchronize_rcu();
 111 }
 112
 113 module_init(ip_vs_wlc_init);
 114 module_exit(ip_vs_wlc_cleanup);
 115 MODULE_LICENSE("GPL");