aboutsummaryrefslogtreecommitdiffstats
path: root/net/sched/sch_sfq.c
blob: fe1508ef0d3d51e7d552a88e253a1d4b0b82fec6 (plain) (blame)
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
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
/*
 * net/sched/sch_sfq.c	Stochastic Fairness Queueing discipline.
 *
 *		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.
 *
 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/string.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/ipv6.h>
#include <linux/skbuff.h>
#include <linux/jhash.h>
#include <net/ip.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>


/*	Stochastic Fairness Queuing algorithm.
	=======================================

	Source:
	Paul E. McKenney "Stochastic Fairness Queuing",
	IEEE INFOCOMM'90 Proceedings, San Francisco, 1990.

	Paul E. McKenney "Stochastic Fairness Queuing",
	"Interworking: Research and Experience", v.2, 1991, p.113-131.


	See also:
	M. Shreedhar and George Varghese "Efficient Fair
	Queuing using Deficit Round Robin", Proc. SIGCOMM 95.


	This is not the thing that is usually called (W)FQ nowadays.
	It does not use any timestamp mechanism, but instead
	processes queues in round-robin order.

	ADVANTAGE:

	- It is very cheap. Both CPU and memory requirements are minimal.

	DRAWBACKS:

	- "Stochastic" -> It is not 100% fair.
	When hash collisions occur, several flows are considered as one.

	- "Round-robin" -> It introduces larger delays than virtual clock
	based schemes, and should not be used for isolating interactive
	traffic	from non-interactive. It means, that this scheduler
	should be used as leaf of CBQ or P3, which put interactive traffic
	to higher priority band.

	We still need true WFQ for top level CSZ, but using WFQ
	for the best effort traffic is absolutely pointless:
	SFQ is superior for this purpose.

	IMPLEMENTATION:
	This implementation limits maximal queue length to 128;
	maximal mtu to 2^15-1; number of hash buckets to 1024.
	The only goal of this restrictions was that all data
	fit into one 4K page :-). Struct sfq_sched_data is
	organized in anti-cache manner: all the data for a bucket
	are scattered over different locations. This is not good,
	but it allowed me to put it into 4K.

	It is easy to increase these values, but not in flight.  */

#define SFQ_DEPTH		128
#define SFQ_HASH_DIVISOR	1024

/* This type should contain at least SFQ_DEPTH*2 values */
typedef unsigned char sfq_index;

struct sfq_head
{
	sfq_index	next;
	sfq_index	prev;
};

struct sfq_sched_data
{
/* Parameters */
	int		perturb_period;
	unsigned	quantum;	/* Allotment per round: MUST BE >= MTU */
	int		limit;

/* Variables */
	struct tcf_proto *filter_list;
	struct timer_list perturb_timer;
	u32		perturbation;
	sfq_index	tail;		/* Index of current slot in round */
	sfq_index	max_depth;	/* Maximal depth */

	sfq_index	ht[SFQ_HASH_DIVISOR];	/* Hash table */
	sfq_index	next[SFQ_DEPTH];	/* Active slots link */
	short		allot[SFQ_DEPTH];	/* Current allotment per slot */
	unsigned short	hash[SFQ_DEPTH];	/* Hash value indexed by slots */
	struct sk_buff_head	qs[SFQ_DEPTH];		/* Slot queue */
	struct sfq_head	dep[SFQ_DEPTH*2];	/* Linked list of slots, indexed by depth */
};

static __inline__ unsigned sfq_fold_hash(struct sfq_sched_data *q, u32 h, u32 h1)
{
	return jhash_2words(h, h1, q->perturbation) & (SFQ_HASH_DIVISOR - 1);
}

static unsigned sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb)
{
	u32 h, h2;

	switch (skb->protocol) {
	case htons(ETH_P_IP):
	{
		const struct iphdr *iph = ip_hdr(skb);
		h = iph->daddr;
		h2 = iph->saddr ^ iph->protocol;
		if (!(iph->frag_off&htons(IP_MF|IP_OFFSET)) &&
		    (iph->protocol == IPPROTO_TCP ||
		     iph->protocol == IPPROTO_UDP ||
		     iph->protocol == IPPROTO_UDPLITE ||
		     iph->protocol == IPPROTO_SCTP ||
		     iph->protocol == IPPROTO_DCCP ||
		     iph->protocol == IPPROTO_ESP))
			h2 ^= *(((u32*)iph) + iph->ihl);
		break;
	}
	case htons(ETH_P_IPV6):
	{
		struct ipv6hdr *iph = ipv6_hdr(skb);
		h = iph->daddr.s6_addr32[3];
		h2 = iph->saddr.s6_addr32[3] ^ iph->nexthdr;
		if (iph->nexthdr == IPPROTO_TCP ||
		    iph->nexthdr == IPPROTO_UDP ||
		    iph->nexthdr == IPPROTO_UDPLITE ||
		    iph->nexthdr == IPPROTO_SCTP ||
		    iph->nexthdr == IPPROTO_DCCP ||
		    iph->nexthdr == IPPROTO_ESP)
			h2 ^= *(u32*)&iph[1];
		break;
	}
	default:
		h = (unsigned long)skb->dst ^ skb->protocol;
		h2 = (unsigned long)skb->sk;
	}

	return sfq_fold_hash(q, h, h2);
}

static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
				 int *qerr)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	struct tcf_result res;
	int result;

	if (TC_H_MAJ(skb->priority) == sch->handle &&
	    TC_H_MIN(skb->priority) > 0 &&
	    TC_H_MIN(skb->priority) <= SFQ_HASH_DIVISOR)
		return TC_H_MIN(skb->priority);

	if (!q->filter_list)
		return sfq_hash(q, skb) + 1;

	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
	result = tc_classify(skb, q->filter_list, &res);
	if (result >= 0) {
#ifdef CONFIG_NET_CLS_ACT
		switch (result) {
		case TC_ACT_STOLEN:
		case TC_ACT_QUEUED:
			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
		case TC_ACT_SHOT:
			return 0;
		}
#endif
		if (TC_H_MIN(res.classid) <= SFQ_HASH_DIVISOR)
			return TC_H_MIN(res.classid);
	}
	return 0;
}

static inline void sfq_link(struct sfq_sched_data *q, sfq_index x)
{
	sfq_index p, n;
	int d = q->qs[x].qlen + SFQ_DEPTH;

	p = d;
	n = q->dep[d].next;
	q->dep[x].next = n;
	q->dep[x].prev = p;
	q->dep[p].next = q->dep[n].prev = x;
}

static inline void sfq_dec(struct sfq_sched_data *q, sfq_index x)
{
	sfq_index p, n;

	n = q->dep[x].next;
	p = q->dep[x].prev;
	q->dep[p].next = n;
	q->dep[n].prev = p;

	if (n == p && q->max_depth == q->qs[x].qlen + 1)
		q->max_depth--;

	sfq_link(q, x);
}

static inline void sfq_inc(struct sfq_sched_data *q, sfq_index x)
{
	sfq_index p, n;
	int d;

	n = q->dep[x].next;
	p = q->dep[x].prev;
	q->dep[p].next = n;
	q->dep[n].prev = p;
	d = q->qs[x].qlen;
	if (q->max_depth < d)
		q->max_depth = d;

	sfq_link(q, x);
}

static unsigned int sfq_drop(struct Qdisc *sch)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	sfq_index d = q->max_depth;
	struct sk_buff *skb;
	unsigned int len;

	/* Queue is full! Find the longest slot and
	   drop a packet from it */

	if (d > 1) {
		sfq_index x = q->dep[d + SFQ_DEPTH].next;
		skb = q->qs[x].prev;
		len = qdisc_pkt_len(skb);
		__skb_unlink(skb, &q->qs[x]);
		kfree_skb(skb);
		sfq_dec(q, x);
		sch->q.qlen--;
		sch->qstats.drops++;
		sch->qstats.backlog -= len;
		return len;
	}

	if (d == 1) {
		/* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */
		d = q->next[q->tail];
		q->next[q->tail] = q->next[d];
		q->allot[q->next[d]] += q->quantum;
		skb = q->qs[d].prev;
		len = qdisc_pkt_len(skb);
		__skb_unlink(skb, &q->qs[d]);
		kfree_skb(skb);
		sfq_dec(q, d);
		sch->q.qlen--;
		q->ht[q->hash[d]] = SFQ_DEPTH;
		sch->qstats.drops++;
		sch->qstats.backlog -= len;
		return len;
	}

	return 0;
}

static int
sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	unsigned int hash;
	sfq_index x;
	int ret;

	hash = sfq_classify(skb, sch, &ret);
	if (hash == 0) {
		if (ret & __NET_XMIT_BYPASS)
			sch->qstats.drops++;
		kfree_skb(skb);
		return ret;
	}
	hash--;

	x = q->ht[hash];
	if (x == SFQ_DEPTH) {
		q->ht[hash] = x = q->dep[SFQ_DEPTH].next;
		q->hash[x] = hash;
	}

	/* If selected queue has length q->limit, this means that
	 * all another queues are empty and that we do simple tail drop,
	 * i.e. drop _this_ packet.
	 */
	if (q->qs[x].qlen >= q->limit)
		return qdisc_drop(skb, sch);

	sch->qstats.backlog += qdisc_pkt_len(skb);
	__skb_queue_tail(&q->qs[x], skb);
	sfq_inc(q, x);
	if (q->qs[x].qlen == 1) {		/* The flow is new */
		if (q->tail == SFQ_DEPTH) {	/* It is the first flow */
			q->tail = x;
			q->next[x] = x;
			q->allot[x] = q->quantum;
		} else {
			q->next[x] = q->next[q->tail];
			q->next[q->tail] = x;
			q->tail = x;
		}
	}
	if (++sch->q.qlen <= q->limit) {
		sch->bstats.bytes += qdisc_pkt_len(skb);
		sch->bstats.packets++;
		return 0;
	}

	sfq_drop(sch);
	return NET_XMIT_CN;
}

static int
sfq_requeue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	unsigned int hash;
	sfq_index x;
	int ret;

	hash = sfq_classify(skb, sch, &ret);
	if (hash == 0) {
		if (ret & __NET_XMIT_BYPASS)
			sch->qstats.drops++;
		kfree_skb(skb);
		return ret;
	}
	hash--;

	x = q->ht[hash];
	if (x == SFQ_DEPTH) {
		q->ht[hash] = x = q->dep[SFQ_DEPTH].next;
		q->hash[x] = hash;
	}

	sch->qstats.backlog += qdisc_pkt_len(skb);
	__skb_queue_head(&q->qs[x], skb);
	/* If selected queue has length q->limit+1, this means that
	 * all another queues are empty and we do simple tail drop.
	 * This packet is still requeued at head of queue, tail packet
	 * is dropped.
	 */
	if (q->qs[x].qlen > q->limit) {
		skb = q->qs[x].prev;
		__skb_unlink(skb, &q->qs[x]);
		sch->qstats.drops++;
		sch->qstats.backlog -= qdisc_pkt_len(skb);
		kfree_skb(skb);
		return NET_XMIT_CN;
	}

	sfq_inc(q, x);
	if (q->qs[x].qlen == 1) {		/* The flow is new */
		if (q->tail == SFQ_DEPTH) {	/* It is the first flow */
			q->tail = x;
			q->next[x] = x;
			q->allot[x] = q->quantum;
		} else {
			q->next[x] = q->next[q->tail];
			q->next[q->tail] = x;
			q->tail = x;
		}
	}

	if (++sch->q.qlen <= q->limit) {
		sch->qstats.requeues++;
		return 0;
	}

	sch->qstats.drops++;
	sfq_drop(sch);
	return NET_XMIT_CN;
}




static struct sk_buff *
sfq_dequeue(struct Qdisc *sch)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	struct sk_buff *skb;
	sfq_index a, old_a;

	/* No active slots */
	if (q->tail == SFQ_DEPTH)
		return NULL;

	a = old_a = q->next[q->tail];

	/* Grab packet */
	skb = __skb_dequeue(&q->qs[a]);
	sfq_dec(q, a);
	sch->q.qlen--;
	sch->qstats.backlog -= qdisc_pkt_len(skb);

	/* Is the slot empty? */
	if (q->qs[a].qlen == 0) {
		q->ht[q->hash[a]] = SFQ_DEPTH;
		a = q->next[a];
		if (a == old_a) {
			q->tail = SFQ_DEPTH;
			return skb;
		}
		q->next[q->tail] = a;
		q->allot[a] += q->quantum;
	} else if ((q->allot[a] -= qdisc_pkt_len(skb)) <= 0) {
		q->tail = a;
		a = q->next[a];
		q->allot[a] += q->quantum;
	}
	return skb;
}

static void
sfq_reset(struct Qdisc *sch)
{
	struct sk_buff *skb;

	while ((skb = sfq_dequeue(sch)) != NULL)
		kfree_skb(skb);
}

static void sfq_perturbation(unsigned long arg)
{
	struct Qdisc *sch = (struct Qdisc *)arg;
	struct sfq_sched_data *q = qdisc_priv(sch);

	q->perturbation = net_random();

	if (q->perturb_period)
		mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
}

static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	struct tc_sfq_qopt *ctl = nla_data(opt);
	unsigned int qlen;

	if (opt->nla_len < nla_attr_size(sizeof(*ctl)))
		return -EINVAL;

	sch_tree_lock(sch);
	q->quantum = ctl->quantum ? : psched_mtu(qdisc_dev(sch));
	q->perturb_period = ctl->perturb_period * HZ;
	if (ctl->limit)
		q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1);

	qlen = sch->q.qlen;
	while (sch->q.qlen > q->limit)
		sfq_drop(sch);
	qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);

	del_timer(&q->perturb_timer);
	if (q->perturb_period) {
		mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
		q->perturbation = net_random();
	}
	sch_tree_unlock(sch);
	return 0;
}

static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	int i;

	q->perturb_timer.function = sfq_perturbation;
	q->perturb_timer.data = (unsigned long)sch;;
	init_timer_deferrable(&q->perturb_timer);

	for (i = 0; i < SFQ_HASH_DIVISOR; i++)
		q->ht[i] = SFQ_DEPTH;

	for (i = 0; i < SFQ_DEPTH; i++) {
		skb_queue_head_init(&q->qs[i]);
		q->dep[i + SFQ_DEPTH].next = i + SFQ_DEPTH;
		q->dep[i + SFQ_DEPTH].prev = i + SFQ_DEPTH;
	}

	q->limit = SFQ_DEPTH - 1;
	q->max_depth = 0;
	q->tail = SFQ_DEPTH;
	if (opt == NULL) {
		q->quantum = psched_mtu(qdisc_dev(sch));
		q->perturb_period = 0;
		q->perturbation = net_random();
	} else {
		int err = sfq_change(sch, opt);
		if (err)
			return err;
	}

	for (i = 0; i < SFQ_DEPTH; i++)
		sfq_link(q, i);
	return 0;
}

static void sfq_destroy(struct Qdisc *sch)
{
	struct sfq_sched_data *q = qdisc_priv(sch);

	tcf_destroy_chain(&q->filter_list);
	q->perturb_period = 0;
	del_timer_sync(&q->perturb_timer);
}

static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	unsigned char *b = skb_tail_pointer(skb);
	struct tc_sfq_qopt opt;

	opt.quantum = q->quantum;
	opt.perturb_period = q->perturb_period / HZ;

	opt.limit = q->limit;
	opt.divisor = SFQ_HASH_DIVISOR;
	opt.flows = q->limit;

	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);

	return skb->len;

nla_put_failure:
	nlmsg_trim(skb, b);
	return -1;
}

static int sfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
			    struct nlattr **tca, unsigned long *arg)
{
	return -EOPNOTSUPP;
}

static unsigned long sfq_get(struct Qdisc *sch, u32 classid)
{
	return 0;
}

static struct tcf_proto **sfq_find_tcf(struct Qdisc *sch, unsigned long cl)
{
	struct sfq_sched_data *q = qdisc_priv(sch);

	if (cl)
		return NULL;
	return &q->filter_list;
}

static int sfq_dump_class(struct Qdisc *sch, unsigned long cl,
			  struct sk_buff *skb, struct tcmsg *tcm)
{
	tcm->tcm_handle |= TC_H_MIN(cl);
	return 0;
}

static int sfq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
				struct gnet_dump *d)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	sfq_index idx = q->ht[cl-1];
	struct gnet_stats_queue qs = { .qlen = q->qs[idx].qlen };
	struct tc_sfq_xstats xstats = { .allot = q->allot[idx] };

	if (gnet_stats_copy_queue(d, &qs) < 0)
		return -1;
	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
}

static void sfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
	struct sfq_sched_data *q = qdisc_priv(sch);
	unsigned int i;

	if (arg->stop)
		return;

	for (i = 0; i < SFQ_HASH_DIVISOR; i++) {
		if (q->ht[i] == SFQ_DEPTH ||
		    arg->count < arg->skip) {
			arg->count++;
			continue;
		}
		if (arg->fn(sch, i + 1, arg) < 0) {
			arg->stop = 1;
			break;
		}
		arg->count++;
	}
}

static const struct Qdisc_class_ops sfq_class_ops = {
	.get		=	sfq_get,
	.change		=	sfq_change_class,
	.tcf_chain	=	sfq_find_tcf,
	.dump		=	sfq_dump_class,
	.dump_stats	=	sfq_dump_class_stats,
	.walk		=	sfq_walk,
};

static struct Qdisc_ops sfq_qdisc_ops __read_mostly = {
	.cl_ops		=	&sfq_class_ops,
	.id		=	"sfq",
	.priv_size	=	sizeof(struct sfq_sched_data),
	.enqueue	=	sfq_enqueue,
	.dequeue	=	sfq_dequeue,
	.requeue	=	sfq_requeue,
	.drop		=	sfq_drop,
	.init		=	sfq_init,
	.reset		=	sfq_reset,
	.destroy	=	sfq_destroy,
	.change		=	NULL,
	.dump		=	sfq_dump,
	.owner		=	THIS_MODULE,
};

static int __init sfq_module_init(void)
{
	return register_qdisc(&sfq_qdisc_ops);
}
static void __exit sfq_module_exit(void)
{
	unregister_qdisc(&sfq_qdisc_ops);
}
module_init(sfq_module_init)
module_exit(sfq_module_exit)
MODULE_LICENSE("GPL");