net/netfilter/ipvs/ip_vs_lc.c

   1 /*
   2  * IPVS:        Least-Connection Scheduling module
   3  *
   4  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   5  *
   6  *              This program is free software; you can redistribute it and/or
   7  *              modify it under the terms of the GNU General Public License
   8  *              as published by the Free Software Foundation; either version
   9  *              2 of the License, or (at your option) any later version.
  10  *
  11  * Changes:
  12  *     Wensong Zhang            :     added the ip_vs_lc_update_svc
  13  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
  14  *
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/kernel.h>
  19
  20 #include <net/ip_vs.h>
  21
  22
  23 static inline unsigned int
  24 ip_vs_lc_dest_overhead(struct ip_vs_dest *dest)
  25 {
  26         /*
  27          * We think the overhead of processing active connections is 256
  28          * times higher than that of inactive connections in average. (This
  29          * 256 times might not be accurate, we will change it later) We
  30          * use the following formula to estimate the overhead now:
  31          *                dest->activeconns*256 + dest->inactconns
  32          */
  33         return (atomic_read(&dest->activeconns) << 8) +
  34                 atomic_read(&dest->inactconns);
  35 }
  36
  37
  38 /*
  39  *      Least Connection scheduling
  40  */
  41 static struct ip_vs_dest *
  42 ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  43 {
  44         struct ip_vs_dest *dest, *least = NULL;
  45         unsigned int loh = 0, doh;
  46
  47         IP_VS_DBG(6, "ip_vs_lc_schedule(): Scheduling...\n");
  48
  49         /*
  50          * Simply select the server with the least number of
  51          *        (activeconns<<5) + inactconns
  52          * Except whose weight is equal to zero.
  53          * If the weight is equal to zero, it means that the server is
  54          * quiesced, the existing connections to the server still get
  55          * served, but no new connection is assigned to the server.
  56          */
  57
  58         list_for_each_entry(dest, &svc->destinations, n_list) {
  59                 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
  60                     atomic_read(&dest->weight) == 0)
  61                         continue;
  62                 doh = ip_vs_lc_dest_overhead(dest);
  63                 if (!least || doh < loh) {
  64                         least = dest;
  65                         loh = doh;
  66                 }
  67         }
  68
  69         if (!least)
  70                 IP_VS_ERR_RL("LC: no destination available\n");
  71         else
  72                 IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
  73                               "inactconns %d\n",
  74                               IP_VS_DBG_ADDR(svc->af, &least->addr),
  75                               ntohs(least->port),
  76                               atomic_read(&least->activeconns),
  77                               atomic_read(&least->inactconns));
  78
  79         return least;
  80 }
  81
  82
  83 static struct ip_vs_scheduler ip_vs_lc_scheduler = {
  84         .name =                 "lc",
  85         .refcnt =               ATOMIC_INIT(0),
  86         .module =               THIS_MODULE,
  87         .n_list =               LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
  88         .schedule =             ip_vs_lc_schedule,
  89 };
  90
  91
  92 static int __init ip_vs_lc_init(void)
  93 {
  94         return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
  95 }
  96
  97 static void __exit ip_vs_lc_cleanup(void)
  98 {
  99         unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
 100 }
 101
 102 module_init(ip_vs_lc_init);
 103 module_exit(ip_vs_lc_cleanup);
 104 MODULE_LICENSE("GPL");