summaryrefslogtreecommitdiffstats
path: root/net/ipv4/ipvs/ip_vs_wrr.c
blob: 749fa044eca53cb6ecda61e8019045d04705973c (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
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
/*
 * IPVS:        Weighted Round-Robin Scheduling module
 *
 * Version:     $Id: ip_vs_wrr.c,v 1.12 2002/09/15 08:14:08 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:
 *     Wensong Zhang            :     changed the ip_vs_wrr_schedule to return dest
 *     Wensong Zhang            :     changed some comestics things for debugging
 *     Wensong Zhang            :     changed for the d-linked destination list
 *     Wensong Zhang            :     added the ip_vs_wrr_update_svc
 *     Julian Anastasov         :     fixed the bug of returning destination
 *                                    with weight 0 when all weights are zero
 *
 */

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

#include <net/ip_vs.h>

/*
 * current destination pointer for weighted round-robin scheduling
 */
struct ip_vs_wrr_mark {
	struct list_head *cl;	/* current list head */
	int cw;			/* current weight */
	int mw;			/* maximum weight */
	int di;			/* decreasing interval */
};


/*
 *    Get the gcd of server weights
 */
static int gcd(int a, int b)
{
	int c;

	while ((c = a % b)) {
		a = b;
		b = c;
	}
	return b;
}

static int ip_vs_wrr_gcd_weight(struct ip_vs_service *svc)
{
	struct ip_vs_dest *dest;
	int weight;
	int g = 0;

	list_for_each_entry(dest, &svc->destinations, n_list) {
		weight = atomic_read(&dest->weight);
		if (weight > 0) {
			if (g > 0)
				g = gcd(weight, g);
			else
				g = weight;
		}
	}
	return g ? g : 1;
}


/*
 *    Get the maximum weight of the service destinations.
 */
static int ip_vs_wrr_max_weight(struct ip_vs_service *svc)
{
	struct ip_vs_dest *dest;
	int weight = 0;

	list_for_each_entry(dest, &svc->destinations, n_list) {
		if (atomic_read(&dest->weight) > weight)
			weight = atomic_read(&dest->weight);
	}

	return weight;
}


static int ip_vs_wrr_init_svc(struct ip_vs_service *svc)
{
	struct ip_vs_wrr_mark *mark;

	/*
	 *    Allocate the mark variable for WRR scheduling
	 */
	mark = kmalloc(sizeof(struct ip_vs_wrr_mark), GFP_ATOMIC);
	if (mark == NULL) {
		IP_VS_ERR("ip_vs_wrr_init_svc(): no memory\n");
		return -ENOMEM;
	}
	mark->cl = &svc->destinations;
	mark->cw = 0;
	mark->mw = ip_vs_wrr_max_weight(svc);
	mark->di = ip_vs_wrr_gcd_weight(svc);
	svc->sched_data = mark;

	return 0;
}


static int ip_vs_wrr_done_svc(struct ip_vs_service *svc)
{
	/*
	 *    Release the mark variable
	 */
	kfree(svc->sched_data);

	return 0;
}


static int ip_vs_wrr_update_svc(struct ip_vs_service *svc)
{
	struct ip_vs_wrr_mark *mark = svc->sched_data;

	mark->cl = &svc->destinations;
	mark->mw = ip_vs_wrr_max_weight(svc);
	mark->di = ip_vs_wrr_gcd_weight(svc);
	if (mark->cw > mark->mw)
		mark->cw = 0;
	return 0;
}


/*
 *    Weighted Round-Robin Scheduling
 */
static struct ip_vs_dest *
ip_vs_wrr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
	struct ip_vs_dest *dest;
	struct ip_vs_wrr_mark *mark = svc->sched_data;
	struct list_head *p;

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

	/*
	 * This loop will always terminate, because mark->cw in (0, max_weight]
	 * and at least one server has its weight equal to max_weight.
	 */
	write_lock(&svc->sched_lock);
	p = mark->cl;
	while (1) {
		if (mark->cl == &svc->destinations) {
			/* it is at the head of the destination list */

			if (mark->cl == mark->cl->next) {
				/* no dest entry */
				dest = NULL;
				goto out;
			}

			mark->cl = svc->destinations.next;
			mark->cw -= mark->di;
			if (mark->cw <= 0) {
				mark->cw = mark->mw;
				/*
				 * Still zero, which means no available servers.
				 */
				if (mark->cw == 0) {
					mark->cl = &svc->destinations;
					IP_VS_INFO("ip_vs_wrr_schedule(): "
						   "no available servers\n");
					dest = NULL;
					goto out;
				}
			}
		} else
			mark->cl = mark->cl->next;

		if (mark->cl != &svc->destinations) {
			/* not at the head of the list */
			dest = list_entry(mark->cl, struct ip_vs_dest, n_list);
			if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
			    atomic_read(&dest->weight) >= mark->cw) {
				/* got it */
				break;
			}
		}

		if (mark->cl == p && mark->cw == mark->di) {
			/* back to the start, and no dest is found.
			   It is only possible when all dests are OVERLOADED */
			dest = NULL;
			goto out;
		}
	}

	IP_VS_DBG(6, "WRR: server %u.%u.%u.%u:%u "
		  "activeconns %d refcnt %d weight %d\n",
		  NIPQUAD(dest->addr), ntohs(dest->port),
		  atomic_read(&dest->activeconns),
		  atomic_read(&dest->refcnt),
		  atomic_read(&dest->weight));

  out:
	write_unlock(&svc->sched_lock);
	return dest;
}


static struct ip_vs_scheduler ip_vs_wrr_scheduler = {
	.name =			"wrr",
	.refcnt =		ATOMIC_INIT(0),
	.module =		THIS_MODULE,
	.init_service =		ip_vs_wrr_init_svc,
	.done_service =		ip_vs_wrr_done_svc,
	.update_service =	ip_vs_wrr_update_svc,
	.schedule =		ip_vs_wrr_schedule,
};

static int __init ip_vs_wrr_init(void)
{
	INIT_LIST_HEAD(&ip_vs_wrr_scheduler.n_list);
	return register_ip_vs_scheduler(&ip_vs_wrr_scheduler) ;
}

static void __exit ip_vs_wrr_cleanup(void)
{
	unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler);
}

module_init(ip_vs_wrr_init);
module_exit(ip_vs_wrr_cleanup);
MODULE_LICENSE("GPL");