summaryrefslogtreecommitdiff
path: root/net/ipv4/ipvs/ip_vs_nq.c
blob: bc2a9e5f2a7b41c61610e64489dfa06b078eec5c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
/*
 * IPVS:        Never Queue scheduling module
 *
 * Version:     $Id: ip_vs_nq.c,v 1.2 2003/06/08 09:31:19 wensong Exp $
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Changes:
 *
 */

/*
 * The NQ algorithm adopts a two-speed model. When there is an idle server
 * available, the job will be sent to the idle server, instead of waiting
 * for a fast one. When there is no idle server available, the job will be
 * sent to the server that minimize its expected delay (The Shortest
 * Expected Delay scheduling algorithm).
 *
 * See the following paper for more information:
 * A. Weinrib and S. Shenker, Greed is not enough: Adaptive load sharing
 * in large heterogeneous systems. In Proceedings IEEE INFOCOM'88,
 * pages 986-994, 1988.
 *
 * Thanks must go to Marko Buuri <marko@buuri.name> for talking NQ to me.
 *
 * The difference between NQ and SED is that NQ can improve overall
 * system utilization.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>

#include <net/ip_vs.h>


static int
ip_vs_nq_init_svc(struct ip_vs_service *svc)
{
	return 0;
}


static int
ip_vs_nq_done_svc(struct ip_vs_service *svc)
{
	return 0;
}


static int
ip_vs_nq_update_svc(struct ip_vs_service *svc)
{
	return 0;
}


static inline unsigned int
ip_vs_nq_dest_overhead(struct ip_vs_dest *dest)
{
	/*
	 * We only use the active connection number in the cost
	 * calculation here.
	 */
	return atomic_read(&dest->activeconns) + 1;
}


/*
 *	Weighted Least Connection scheduling
 */
static struct ip_vs_dest *
ip_vs_nq_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
	struct ip_vs_dest *dest, *least = NULL;
	unsigned int loh = 0, doh;

	IP_VS_DBG(6, "ip_vs_nq_schedule(): Scheduling...\n");

	/*
	 * We calculate the load of each dest server as follows:
	 *	(server expected overhead) / dest->weight
	 *
	 * Remember -- no floats in kernel mode!!!
	 * The comparison of h1*w2 > h2*w1 is equivalent to that of
	 *		  h1/w1 > h2/w2
	 * if every weight is larger than zero.
	 *
	 * The server with weight=0 is quiesced and will not receive any
	 * new connections.
	 */

	list_for_each_entry(dest, &svc->destinations, n_list) {

		if (dest->flags & IP_VS_DEST_F_OVERLOAD ||
		    !atomic_read(&dest->weight))
			continue;

		doh = ip_vs_nq_dest_overhead(dest);

		/* return the server directly if it is idle */
		if (atomic_read(&dest->activeconns) == 0) {
			least = dest;
			loh = doh;
			goto out;
		}

		if (!least ||
		    (loh * atomic_read(&dest->weight) >
		     doh * atomic_read(&least->weight))) {
			least = dest;
			loh = doh;
		}
	}

	if (!least)
		return NULL;

  out:
	IP_VS_DBG(6, "NQ: server %u.%u.%u.%u:%u "
		  "activeconns %d refcnt %d weight %d overhead %d\n",
		  NIPQUAD(least->addr), ntohs(least->port),
		  atomic_read(&least->activeconns),
		  atomic_read(&least->refcnt),
		  atomic_read(&least->weight), loh);

	return least;
}


static struct ip_vs_scheduler ip_vs_nq_scheduler =
{
	.name =			"nq",
	.refcnt =		ATOMIC_INIT(0),
	.module =		THIS_MODULE,
	.init_service =		ip_vs_nq_init_svc,
	.done_service =		ip_vs_nq_done_svc,
	.update_service =	ip_vs_nq_update_svc,
	.schedule =		ip_vs_nq_schedule,
};


static int __init ip_vs_nq_init(void)
{
	INIT_LIST_HEAD(&ip_vs_nq_scheduler.n_list);
	return register_ip_vs_scheduler(&ip_vs_nq_scheduler);
}

static void __exit ip_vs_nq_cleanup(void)
{
	unregister_ip_vs_scheduler(&ip_vs_nq_scheduler);
}

module_init(ip_vs_nq_init);
module_exit(ip_vs_nq_cleanup);
MODULE_LICENSE("GPL");