release/src-rt-6.x.4708/linux/linux-2.6.36/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 #define KMSG_COMPONENT "IPVS"
  18 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  19
  20 #include <linux/module.h>
  21 #include <linux/kernel.h>
  22
  23 #include <net/ip_vs.h>
  24
  25
  26 static inline unsigned int
  27 ip_vs_lc_dest_overhead(struct ip_vs_dest *dest)
  28 {
  29         /*
  30          * We think the overhead of processing active connections is 256
  31          * times higher than that of inactive connections in average. (This
  32          * 256 times might not be accurate, we will change it later) We
  33          * use the following formula to estimate the overhead now:
  34          *                dest->activeconns*256 + dest->inactconns
  35          */
  36         return (atomic_read(&dest->activeconns) << 8) +
  37                 atomic_read(&dest->inactconns);
  38 }
  39
  40
  41 /*
  42  *      Least Connection scheduling
  43  */
  44 static struct ip_vs_dest *
  45 ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  46 {
  47         struct ip_vs_dest *dest, *least = NULL;
  48         unsigned int loh = 0, doh;
  49
  50         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
  51
  52         /*
  53          * Simply select the server with the least number of
  54          *        (activeconns<<5) + inactconns
  55          * Except whose weight is equal to zero.
  56          * If the weight is equal to zero, it means that the server is
  57          * quiesced, the existing connections to the server still get
  58          * served, but no new connection is assigned to the server.
  59          */
  60
  61         list_for_each_entry(dest, &svc->destinations, n_list) {
  62                 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
  63                     atomic_read(&dest->weight) == 0)
  64                         continue;
  65                 doh = ip_vs_lc_dest_overhead(dest);
  66                 if (!least || doh < loh) {
  67                         least = dest;
  68                         loh = doh;
  69                 }
  70         }
  71
  72         if (!least)
  73                 IP_VS_ERR_RL("LC: no destination available\n");
  74         else
  75                 IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
  76                               "inactconns %d\n",
  77                               IP_VS_DBG_ADDR(svc->af, &least->addr),
  78                               ntohs(least->port),
  79                               atomic_read(&least->activeconns),
  80                               atomic_read(&least->inactconns));
  81
  82         return least;
  83 }
  84
  85
  86 static struct ip_vs_scheduler ip_vs_lc_scheduler = {
  87         .name =                 "lc",
  88         .refcnt =               ATOMIC_INIT(0),
  89         .module =               THIS_MODULE,
  90         .n_list =               LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
  91         .schedule =             ip_vs_lc_schedule,
  92 };
  93
  94
  95 static int __init ip_vs_lc_init(void)
  96 {
  97         return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
  98 }
  99
 100 static void __exit ip_vs_lc_cleanup(void)
 101 {
 102         unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
 103 }
 104
 105 module_init(ip_vs_lc_init);
 106 module_exit(ip_vs_lc_cleanup);
 107 MODULE_LICENSE("GPL");