blob: bc2a9e5f2a7b41c61610e64489dfa06b078eec5c [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * IPVS: Never Queue scheduling module
3 *
4 * Version: $Id: ip_vs_nq.c,v 1.2 2003/06/08 09:31:19 wensong Exp $
5 *
6 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version
11 * 2 of the License, or (at your option) any later version.
12 *
13 * Changes:
14 *
15 */
16
17/*
18 * The NQ algorithm adopts a two-speed model. When there is an idle server
19 * available, the job will be sent to the idle server, instead of waiting
20 * for a fast one. When there is no idle server available, the job will be
21 * sent to the server that minimize its expected delay (The Shortest
22 * Expected Delay scheduling algorithm).
23 *
24 * See the following paper for more information:
25 * A. Weinrib and S. Shenker, Greed is not enough: Adaptive load sharing
26 * in large heterogeneous systems. In Proceedings IEEE INFOCOM'88,
27 * pages 986-994, 1988.
28 *
29 * Thanks must go to Marko Buuri <marko@buuri.name> for talking NQ to me.
30 *
31 * The difference between NQ and SED is that NQ can improve overall
32 * system utilization.
33 *
34 */
35
36#include <linux/module.h>
37#include <linux/kernel.h>
38
39#include <net/ip_vs.h>
40
41
42static int
43ip_vs_nq_init_svc(struct ip_vs_service *svc)
44{
45 return 0;
46}
47
48
49static int
50ip_vs_nq_done_svc(struct ip_vs_service *svc)
51{
52 return 0;
53}
54
55
56static int
57ip_vs_nq_update_svc(struct ip_vs_service *svc)
58{
59 return 0;
60}
61
62
63static inline unsigned int
64ip_vs_nq_dest_overhead(struct ip_vs_dest *dest)
65{
66 /*
67 * We only use the active connection number in the cost
68 * calculation here.
69 */
70 return atomic_read(&dest->activeconns) + 1;
71}
72
73
74/*
75 * Weighted Least Connection scheduling
76 */
77static struct ip_vs_dest *
78ip_vs_nq_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
79{
80 struct ip_vs_dest *dest, *least = NULL;
81 unsigned int loh = 0, doh;
82
83 IP_VS_DBG(6, "ip_vs_nq_schedule(): Scheduling...\n");
84
85 /*
86 * We calculate the load of each dest server as follows:
87 * (server expected overhead) / dest->weight
88 *
89 * Remember -- no floats in kernel mode!!!
90 * The comparison of h1*w2 > h2*w1 is equivalent to that of
91 * h1/w1 > h2/w2
92 * if every weight is larger than zero.
93 *
94 * The server with weight=0 is quiesced and will not receive any
95 * new connections.
96 */
97
98 list_for_each_entry(dest, &svc->destinations, n_list) {
99
100 if (dest->flags & IP_VS_DEST_F_OVERLOAD ||
101 !atomic_read(&dest->weight))
102 continue;
103
104 doh = ip_vs_nq_dest_overhead(dest);
105
106 /* return the server directly if it is idle */
107 if (atomic_read(&dest->activeconns) == 0) {
108 least = dest;
109 loh = doh;
110 goto out;
111 }
112
113 if (!least ||
114 (loh * atomic_read(&dest->weight) >
115 doh * atomic_read(&least->weight))) {
116 least = dest;
117 loh = doh;
118 }
119 }
120
121 if (!least)
122 return NULL;
123
124 out:
125 IP_VS_DBG(6, "NQ: server %u.%u.%u.%u:%u "
126 "activeconns %d refcnt %d weight %d overhead %d\n",
127 NIPQUAD(least->addr), ntohs(least->port),
128 atomic_read(&least->activeconns),
129 atomic_read(&least->refcnt),
130 atomic_read(&least->weight), loh);
131
132 return least;
133}
134
135
136static struct ip_vs_scheduler ip_vs_nq_scheduler =
137{
138 .name = "nq",
139 .refcnt = ATOMIC_INIT(0),
140 .module = THIS_MODULE,
141 .init_service = ip_vs_nq_init_svc,
142 .done_service = ip_vs_nq_done_svc,
143 .update_service = ip_vs_nq_update_svc,
144 .schedule = ip_vs_nq_schedule,
145};
146
147
148static int __init ip_vs_nq_init(void)
149{
150 INIT_LIST_HEAD(&ip_vs_nq_scheduler.n_list);
151 return register_ip_vs_scheduler(&ip_vs_nq_scheduler);
152}
153
154static void __exit ip_vs_nq_cleanup(void)
155{
156 unregister_ip_vs_scheduler(&ip_vs_nq_scheduler);
157}
158
159module_init(ip_vs_nq_init);
160module_exit(ip_vs_nq_cleanup);
161MODULE_LICENSE("GPL");