aboutsummaryrefslogtreecommitdiffstats
path: root/net/ipv4/ipvs/ip_vs_lblc.c
blob: 7a6a319f544a0390b85f17a200d7360b429cc1c2 (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
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
/*
 * IPVS:        Locality-Based Least-Connection scheduling module
 *
 * Authors:     Wensong Zhang <wensong@gnuchina.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:
 *     Martin Hamilton         :    fixed the terrible locking bugs
 *                                   *lock(tbl->lock) ==> *lock(&tbl->lock)
 *     Wensong Zhang           :    fixed the uninitilized tbl->lock bug
 *     Wensong Zhang           :    added doing full expiration check to
 *                                   collect stale entries of 24+ hours when
 *                                   no partial expire check in a half hour
 *     Julian Anastasov        :    replaced del_timer call with del_timer_sync
 *                                   to avoid the possible race between timer
 *                                   handler and del_timer thread in SMP
 *
 */

/*
 * The lblc algorithm is as follows (pseudo code):
 *
 *       if cachenode[dest_ip] is null then
 *               n, cachenode[dest_ip] <- {weighted least-conn node};
 *       else
 *               n <- cachenode[dest_ip];
 *               if (n is dead) OR
 *                  (n.conns>n.weight AND
 *                   there is a node m with m.conns<m.weight/2) then
 *                 n, cachenode[dest_ip] <- {weighted least-conn node};
 *
 *       return n;
 *
 * Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
 * me to write this module.
 */

#include <linux/ip.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/jiffies.h>

/* for sysctl */
#include <linux/fs.h>
#include <linux/sysctl.h>

#include <net/ip_vs.h>


/*
 *    It is for garbage collection of stale IPVS lblc entries,
 *    when the table is full.
 */
#define CHECK_EXPIRE_INTERVAL   (60*HZ)
#define ENTRY_TIMEOUT           (6*60*HZ)

/*
 *    It is for full expiration check.
 *    When there is no partial expiration check (garbage collection)
 *    in a half hour, do a full expiration check to collect stale
 *    entries that haven't been touched for a day.
 */
#define COUNT_FOR_FULL_EXPIRATION   30
static int sysctl_ip_vs_lblc_expiration = 24*60*60*HZ;


/*
 *     for IPVS lblc entry hash table
 */
#ifndef CONFIG_IP_VS_LBLC_TAB_BITS
#define CONFIG_IP_VS_LBLC_TAB_BITS      10
#endif
#define IP_VS_LBLC_TAB_BITS     CONFIG_IP_VS_LBLC_TAB_BITS
#define IP_VS_LBLC_TAB_SIZE     (1 << IP_VS_LBLC_TAB_BITS)
#define IP_VS_LBLC_TAB_MASK     (IP_VS_LBLC_TAB_SIZE - 1)


/*
 *      IPVS lblc entry represents an association between destination
 *      IP address and its destination server
 */
struct ip_vs_lblc_entry {
	struct list_head        list;
	__be32                  addr;           /* destination IP address */
	struct ip_vs_dest       *dest;          /* real server (cache) */
	unsigned long           lastuse;        /* last used time */
};


/*
 *      IPVS lblc hash table
 */
struct ip_vs_lblc_table {
	rwlock_t	        lock;           /* lock for this table */
	struct list_head        bucket[IP_VS_LBLC_TAB_SIZE];  /* hash bucket */
	atomic_t                entries;        /* number of entries */
	int                     max_size;       /* maximum size of entries */
	struct timer_list       periodic_timer; /* collect stale entries */
	int                     rover;          /* rover for expire check */
	int                     counter;        /* counter for no expire */
};


/*
 *      IPVS LBLC sysctl table
 */

static ctl_table vs_vars_table[] = {
	{
		.procname	= "lblc_expiration",
		.data		= &sysctl_ip_vs_lblc_expiration,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec_jiffies,
	},
	{ .ctl_name = 0 }
};

static struct ctl_table_header * sysctl_header;

/*
 *      new/free a ip_vs_lblc_entry, which is a mapping of a destionation
 *      IP address to a server.
 */
static inline struct ip_vs_lblc_entry *
ip_vs_lblc_new(__be32 daddr, struct ip_vs_dest *dest)
{
	struct ip_vs_lblc_entry *en;

	en = kmalloc(sizeof(struct ip_vs_lblc_entry), GFP_ATOMIC);
	if (en == NULL) {
		IP_VS_ERR("ip_vs_lblc_new(): no memory\n");
		return NULL;
	}

	INIT_LIST_HEAD(&en->list);
	en->addr = daddr;

	atomic_inc(&dest->refcnt);
	en->dest = dest;

	return en;
}


static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry *en)
{
	list_del(&en->list);
	/*
	 * We don't kfree dest because it is refered either by its service
	 * or the trash dest list.
	 */
	atomic_dec(&en->dest->refcnt);
	kfree(en);
}


/*
 *	Returns hash value for IPVS LBLC entry
 */
static inline unsigned ip_vs_lblc_hashkey(__be32 addr)
{
	return (ntohl(addr)*2654435761UL) & IP_VS_LBLC_TAB_MASK;
}


/*
 *	Hash an entry in the ip_vs_lblc_table.
 *	returns bool success.
 */
static int
ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
{
	unsigned hash;

	if (!list_empty(&en->list)) {
		IP_VS_ERR("ip_vs_lblc_hash(): request for already hashed, "
			  "called from %p\n", __builtin_return_address(0));
		return 0;
	}

	/*
	 *	Hash by destination IP address
	 */
	hash = ip_vs_lblc_hashkey(en->addr);

	write_lock(&tbl->lock);
	list_add(&en->list, &tbl->bucket[hash]);
	atomic_inc(&tbl->entries);
	write_unlock(&tbl->lock);

	return 1;
}


/*
 *  Get ip_vs_lblc_entry associated with supplied parameters.
 */
static inline struct ip_vs_lblc_entry *
ip_vs_lblc_get(struct ip_vs_lblc_table *tbl, __be32 addr)
{
	unsigned hash;
	struct ip_vs_lblc_entry *en;

	hash = ip_vs_lblc_hashkey(addr);

	read_lock(&tbl->lock);

	list_for_each_entry(en, &tbl->bucket[hash], list) {
		if (en->addr == addr) {
			/* HIT */
			read_unlock(&tbl->lock);
			return en;
		}
	}

	read_unlock(&tbl->lock);

	return NULL;
}


/*
 *      Flush all the entries of the specified table.
 */
static void ip_vs_lblc_flush(struct ip_vs_lblc_table *tbl)
{
	int i;
	struct ip_vs_lblc_entry *en, *nxt;

	for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
		write_lock(&tbl->lock);
		list_for_each_entry_safe(en, nxt, &tbl->bucket[i], list) {
			ip_vs_lblc_free(en);
			atomic_dec(&tbl->entries);
		}
		write_unlock(&tbl->lock);
	}
}


static inline void ip_vs_lblc_full_check(struct ip_vs_lblc_table *tbl)
{
	unsigned long now = jiffies;
	int i, j;
	struct ip_vs_lblc_entry *en, *nxt;

	for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
		j = (j + 1) & IP_VS_LBLC_TAB_MASK;

		write_lock(&tbl->lock);
		list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
			if (time_before(now,
					en->lastuse + sysctl_ip_vs_lblc_expiration))
				continue;

			ip_vs_lblc_free(en);
			atomic_dec(&tbl->entries);
		}
		write_unlock(&tbl->lock);
	}
	tbl->rover = j;
}


/*
 *      Periodical timer handler for IPVS lblc table
 *      It is used to collect stale entries when the number of entries
 *      exceeds the maximum size of the table.
 *
 *      Fixme: we probably need more complicated algorithm to collect
 *             entries that have not been used for a long time even
 *             if the number of entries doesn't exceed the maximum size
 *             of the table.
 *      The full expiration check is for this purpose now.
 */
static void ip_vs_lblc_check_expire(unsigned long data)
{
	struct ip_vs_lblc_table *tbl;
	unsigned long now = jiffies;
	int goal;
	int i, j;
	struct ip_vs_lblc_entry *en, *nxt;

	tbl = (struct ip_vs_lblc_table *)data;

	if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
		/* do full expiration check */
		ip_vs_lblc_full_check(tbl);
		tbl->counter = 1;
		goto out;
	}

	if (atomic_read(&tbl->entries) <= tbl->max_size) {
		tbl->counter++;
		goto out;
	}

	goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
	if (goal > tbl->max_size/2)
		goal = tbl->max_size/2;

	for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
		j = (j + 1) & IP_VS_LBLC_TAB_MASK;

		write_lock(&tbl->lock);
		list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
			if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
				continue;

			ip_vs_lblc_free(en);
			atomic_dec(&tbl->entries);
			goal--;
		}
		write_unlock(&tbl->lock);
		if (goal <= 0)
			break;
	}
	tbl->rover = j;

  out:
	mod_timer(&tbl->periodic_timer, jiffies+CHECK_EXPIRE_INTERVAL);
}


static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
{
	int i;
	struct ip_vs_lblc_table *tbl;

	/*
	 *    Allocate the ip_vs_lblc_table for this service
	 */
	tbl = kmalloc(sizeof(struct ip_vs_lblc_table), GFP_ATOMIC);
	if (tbl == NULL) {
		IP_VS_ERR("ip_vs_lblc_init_svc(): no memory\n");
		return -ENOMEM;
	}
	svc->sched_data = tbl;
	IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
		  "current service\n",
		  sizeof(struct ip_vs_lblc_table));

	/*
	 *    Initialize the hash buckets
	 */
	for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
		INIT_LIST_HEAD(&tbl->bucket[i]);
	}
	rwlock_init(&tbl->lock);
	tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
	tbl->rover = 0;
	tbl->counter = 1;

	/*
	 *    Hook periodic timer for garbage collection
	 */
	setup_timer(&tbl->periodic_timer, ip_vs_lblc_check_expire,
			(unsigned long)tbl);
	tbl->periodic_timer.expires = jiffies+CHECK_EXPIRE_INTERVAL;
	add_timer(&tbl->periodic_timer);

	return 0;
}


static int ip_vs_lblc_done_svc(struct ip_vs_service *svc)
{
	struct ip_vs_lblc_table *tbl = svc->sched_data;

	/* remove periodic timer */
	del_timer_sync(&tbl->periodic_timer);

	/* got to clean up table entries here */
	ip_vs_lblc_flush(tbl);

	/* release the table itself */
	kfree(svc->sched_data);
	IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
		  sizeof(struct ip_vs_lblc_table));

	return 0;
}


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


static inline struct ip_vs_dest *
__ip_vs_wlc_schedule(struct ip_vs_service *svc, struct iphdr *iph)
{
	struct ip_vs_dest *dest, *least;
	int loh, doh;

	/*
	 * We think the overhead of processing active connections is fifty
	 * times higher than that of inactive connections in average. (This
	 * fifty times might not be accurate, we will change it later.) We
	 * use the following formula to estimate the overhead:
	 *                dest->activeconns*50 + dest->inactconns
	 * and the load:
	 *                (dest 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 connection.
	 */
	list_for_each_entry(dest, &svc->destinations, n_list) {
		if (dest->flags & IP_VS_DEST_F_OVERLOAD)
			continue;
		if (atomic_read(&dest->weight) > 0) {
			least = dest;
			loh = atomic_read(&least->activeconns) * 50
				+ atomic_read(&least->inactconns);
			goto nextstage;
		}
	}
	return NULL;

	/*
	 *    Find the destination with the least load.
	 */
  nextstage:
	list_for_each_entry_continue(dest, &svc->destinations, n_list) {
		if (dest->flags & IP_VS_DEST_F_OVERLOAD)
			continue;

		doh = atomic_read(&dest->activeconns) * 50
			+ atomic_read(&dest->inactconns);
		if (loh * atomic_read(&dest->weight) >
		    doh * atomic_read(&least->weight)) {
			least = dest;
			loh = doh;
		}
	}

	IP_VS_DBG(6, "LBLC: server %d.%d.%d.%d:%d "
		  "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;
}


/*
 *   If this destination server is overloaded and there is a less loaded
 *   server, then return true.
 */
static inline int
is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
{
	if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
		struct ip_vs_dest *d;

		list_for_each_entry(d, &svc->destinations, n_list) {
			if (atomic_read(&d->activeconns)*2
			    < atomic_read(&d->weight)) {
				return 1;
			}
		}
	}
	return 0;
}


/*
 *    Locality-Based (weighted) Least-Connection scheduling
 */
static struct ip_vs_dest *
ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
	struct ip_vs_dest *dest;
	struct ip_vs_lblc_table *tbl;
	struct ip_vs_lblc_entry *en;
	struct iphdr *iph = ip_hdr(skb);

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

	tbl = (struct ip_vs_lblc_table *)svc->sched_data;
	en = ip_vs_lblc_get(tbl, iph->daddr);
	if (en == NULL) {
		dest = __ip_vs_wlc_schedule(svc, iph);
		if (dest == NULL) {
			IP_VS_DBG(1, "no destination available\n");
			return NULL;
		}
		en = ip_vs_lblc_new(iph->daddr, dest);
		if (en == NULL) {
			return NULL;
		}
		ip_vs_lblc_hash(tbl, en);
	} else {
		dest = en->dest;
		if (!(dest->flags & IP_VS_DEST_F_AVAILABLE)
		    || atomic_read(&dest->weight) <= 0
		    || is_overloaded(dest, svc)) {
			dest = __ip_vs_wlc_schedule(svc, iph);
			if (dest == NULL) {
				IP_VS_DBG(1, "no destination available\n");
				return NULL;
			}
			atomic_dec(&en->dest->refcnt);
			atomic_inc(&dest->refcnt);
			en->dest = dest;
		}
	}
	en->lastuse = jiffies;

	IP_VS_DBG(6, "LBLC: destination IP address %u.%u.%u.%u "
		  "--> server %u.%u.%u.%u:%d\n",
		  NIPQUAD(en->addr),
		  NIPQUAD(dest->addr),
		  ntohs(dest->port));

	return dest;
}


/*
 *      IPVS LBLC Scheduler structure
 */
static struct ip_vs_scheduler ip_vs_lblc_scheduler =
{
	.name =			"lblc",
	.refcnt =		ATOMIC_INIT(0),
	.module =		THIS_MODULE,
	.n_list =		LIST_HEAD_INIT(ip_vs_lblc_scheduler.n_list),
	.init_service =		ip_vs_lblc_init_svc,
	.done_service =		ip_vs_lblc_done_svc,
	.update_service =	ip_vs_lblc_update_svc,
	.schedule =		ip_vs_lblc_schedule,
};


static int __init ip_vs_lblc_init(void)
{
	int ret;

	sysctl_header = register_sysctl_paths(net_vs_ctl_path, vs_vars_table);
	ret = register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
	if (ret)
		unregister_sysctl_table(sysctl_header);
	return ret;
}


static void __exit ip_vs_lblc_cleanup(void)
{
	unregister_sysctl_table(sysctl_header);
	unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
}


module_init(ip_vs_lblc_init);
module_exit(ip_vs_lblc_cleanup);
MODULE_LICENSE("GPL");