LXR linux/net/netfilter/ipvs/ip_vs

   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
  26static inline unsigned int
  27ip_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 */
  44static struct ip_vs_dest *
  45ip_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
  86static 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
  95static int __init ip_vs_lc_init(void)
  96{
  97        return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
  98}
  99
 100static void __exit ip_vs_lc_cleanup(void)
 101{
 102        unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
 103}
 104
 105module_init(ip_vs_lc_init);
 106module_exit(ip_vs_lc_cleanup);
 107MODULE_LICENSE("GPL");
 108