summaryrefslogtreecommitdiff
path: root/net/sched/sch_hhf.c
blob: 44d9efe1a96a89bdb44a6d48071b3eed90fd5554 (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
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
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
// SPDX-License-Identifier: GPL-2.0-only
/* net/sched/sch_hhf.c		Heavy-Hitter Filter (HHF)
 *
 * Copyright (C) 2013 Terry Lam <vtlam@google.com>
 * Copyright (C) 2013 Nandita Dukkipati <nanditad@google.com>
 */

#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/vmalloc.h>
#include <linux/siphash.h>
#include <net/pkt_sched.h>
#include <net/sock.h>

/*	Heavy-Hitter Filter (HHF)
 *
 * Principles :
 * Flows are classified into two buckets: non-heavy-hitter and heavy-hitter
 * buckets. Initially, a new flow starts as non-heavy-hitter. Once classified
 * as heavy-hitter, it is immediately switched to the heavy-hitter bucket.
 * The buckets are dequeued by a Weighted Deficit Round Robin (WDRR) scheduler,
 * in which the heavy-hitter bucket is served with less weight.
 * In other words, non-heavy-hitters (e.g., short bursts of critical traffic)
 * are isolated from heavy-hitters (e.g., persistent bulk traffic) and also have
 * higher share of bandwidth.
 *
 * To capture heavy-hitters, we use the "multi-stage filter" algorithm in the
 * following paper:
 * [EV02] C. Estan and G. Varghese, "New Directions in Traffic Measurement and
 * Accounting", in ACM SIGCOMM, 2002.
 *
 * Conceptually, a multi-stage filter comprises k independent hash functions
 * and k counter arrays. Packets are indexed into k counter arrays by k hash
 * functions, respectively. The counters are then increased by the packet sizes.
 * Therefore,
 *    - For a heavy-hitter flow: *all* of its k array counters must be large.
 *    - For a non-heavy-hitter flow: some of its k array counters can be large
 *      due to hash collision with other small flows; however, with high
 *      probability, not *all* k counters are large.
 *
 * By the design of the multi-stage filter algorithm, the false negative rate
 * (heavy-hitters getting away uncaptured) is zero. However, the algorithm is
 * susceptible to false positives (non-heavy-hitters mistakenly classified as
 * heavy-hitters).
 * Therefore, we also implement the following optimizations to reduce false
 * positives by avoiding unnecessary increment of the counter values:
 *    - Optimization O1: once a heavy-hitter is identified, its bytes are not
 *        accounted in the array counters. This technique is called "shielding"
 *        in Section 3.3.1 of [EV02].
 *    - Optimization O2: conservative update of counters
 *                       (Section 3.3.2 of [EV02]),
 *        New counter value = max {old counter value,
 *                                 smallest counter value + packet bytes}
 *
 * Finally, we refresh the counters periodically since otherwise the counter
 * values will keep accumulating.
 *
 * Once a flow is classified as heavy-hitter, we also save its per-flow state
 * in an exact-matching flow table so that its subsequent packets can be
 * dispatched to the heavy-hitter bucket accordingly.
 *
 *
 * At a high level, this qdisc works as follows:
 * Given a packet p:
 *   - If the flow-id of p (e.g., TCP 5-tuple) is already in the exact-matching
 *     heavy-hitter flow table, denoted table T, then send p to the heavy-hitter
 *     bucket.
 *   - Otherwise, forward p to the multi-stage filter, denoted filter F
 *        + If F decides that p belongs to a non-heavy-hitter flow, then send p
 *          to the non-heavy-hitter bucket.
 *        + Otherwise, if F decides that p belongs to a new heavy-hitter flow,
 *          then set up a new flow entry for the flow-id of p in the table T and
 *          send p to the heavy-hitter bucket.
 *
 * In this implementation:
 *   - T is a fixed-size hash-table with 1024 entries. Hash collision is
 *     resolved by linked-list chaining.
 *   - F has four counter arrays, each array containing 1024 32-bit counters.
 *     That means 4 * 1024 * 32 bits = 16KB of memory.
 *   - Since each array in F contains 1024 counters, 10 bits are sufficient to
 *     index into each array.
 *     Hence, instead of having four hash functions, we chop the 32-bit
 *     skb-hash into three 10-bit chunks, and the remaining 10-bit chunk is
 *     computed as XOR sum of those three chunks.
 *   - We need to clear the counter arrays periodically; however, directly
 *     memsetting 16KB of memory can lead to cache eviction and unwanted delay.
 *     So by representing each counter by a valid bit, we only need to reset
 *     4K of 1 bit (i.e. 512 bytes) instead of 16KB of memory.
 *   - The Deficit Round Robin engine is taken from fq_codel implementation
 *     (net/sched/sch_fq_codel.c). Note that wdrr_bucket corresponds to
 *     fq_codel_flow in fq_codel implementation.
 *
 */

/* Non-configurable parameters */
#define HH_FLOWS_CNT	 1024  /* number of entries in exact-matching table T */
#define HHF_ARRAYS_CNT	 4     /* number of arrays in multi-stage filter F */
#define HHF_ARRAYS_LEN	 1024  /* number of counters in each array of F */
#define HHF_BIT_MASK_LEN 10    /* masking 10 bits */
#define HHF_BIT_MASK	 0x3FF /* bitmask of 10 bits */

#define WDRR_BUCKET_CNT  2     /* two buckets for Weighted DRR */
enum wdrr_bucket_idx {
	WDRR_BUCKET_FOR_HH	= 0, /* bucket id for heavy-hitters */
	WDRR_BUCKET_FOR_NON_HH	= 1  /* bucket id for non-heavy-hitters */
};

#define hhf_time_before(a, b)	\
	(typecheck(u32, a) && typecheck(u32, b) && ((s32)((a) - (b)) < 0))

/* Heavy-hitter per-flow state */
struct hh_flow_state {
	u32		 hash_id;	/* hash of flow-id (e.g. TCP 5-tuple) */
	u32		 hit_timestamp;	/* last time heavy-hitter was seen */
	struct list_head flowchain;	/* chaining under hash collision */
};

/* Weighted Deficit Round Robin (WDRR) scheduler */
struct wdrr_bucket {
	struct sk_buff	  *head;
	struct sk_buff	  *tail;
	struct list_head  bucketchain;
	int		  deficit;
};

struct hhf_sched_data {
	struct wdrr_bucket buckets[WDRR_BUCKET_CNT];
	siphash_key_t	   perturbation;   /* hash perturbation */
	u32		   quantum;        /* psched_mtu(qdisc_dev(sch)); */
	u32		   drop_overlimit; /* number of times max qdisc packet
					    * limit was hit
					    */
	struct list_head   *hh_flows;       /* table T (currently active HHs) */
	u32		   hh_flows_limit;            /* max active HH allocs */
	u32		   hh_flows_overlimit; /* num of disallowed HH allocs */
	u32		   hh_flows_total_cnt;          /* total admitted HHs */
	u32		   hh_flows_current_cnt;        /* total current HHs  */
	u32		   *hhf_arrays[HHF_ARRAYS_CNT]; /* HH filter F */
	u32		   hhf_arrays_reset_timestamp;  /* last time hhf_arrays
							 * was reset
							 */
	unsigned long	   *hhf_valid_bits[HHF_ARRAYS_CNT]; /* shadow valid bits
							     * of hhf_arrays
							     */
	/* Similar to the "new_flows" vs. "old_flows" concept in fq_codel DRR */
	struct list_head   new_buckets; /* list of new buckets */
	struct list_head   old_buckets; /* list of old buckets */

	/* Configurable HHF parameters */
	u32		   hhf_reset_timeout; /* interval to reset counter
					       * arrays in filter F
					       * (default 40ms)
					       */
	u32		   hhf_admit_bytes;   /* counter thresh to classify as
					       * HH (default 128KB).
					       * With these default values,
					       * 128KB / 40ms = 25 Mbps
					       * i.e., we expect to capture HHs
					       * sending > 25 Mbps.
					       */
	u32		   hhf_evict_timeout; /* aging threshold to evict idle
					       * HHs out of table T. This should
					       * be large enough to avoid
					       * reordering during HH eviction.
					       * (default 1s)
					       */
	u32		   hhf_non_hh_weight; /* WDRR weight for non-HHs
					       * (default 2,
					       *  i.e., non-HH : HH = 2 : 1)
					       */
};

static u32 hhf_time_stamp(void)
{
	return jiffies;
}

/* Looks up a heavy-hitter flow in a chaining list of table T. */
static struct hh_flow_state *seek_list(const u32 hash,
				       struct list_head *head,
				       struct hhf_sched_data *q)
{
	struct hh_flow_state *flow, *next;
	u32 now = hhf_time_stamp();

	if (list_empty(head))
		return NULL;

	list_for_each_entry_safe(flow, next, head, flowchain) {
		u32 prev = flow->hit_timestamp + q->hhf_evict_timeout;

		if (hhf_time_before(prev, now)) {
			/* Delete expired heavy-hitters, but preserve one entry
			 * to avoid kzalloc() when next time this slot is hit.
			 */
			if (list_is_last(&flow->flowchain, head))
				return NULL;
			list_del(&flow->flowchain);
			kfree(flow);
			q->hh_flows_current_cnt--;
		} else if (flow->hash_id == hash) {
			return flow;
		}
	}
	return NULL;
}

/* Returns a flow state entry for a new heavy-hitter.  Either reuses an expired
 * entry or dynamically alloc a new entry.
 */
static struct hh_flow_state *alloc_new_hh(struct list_head *head,
					  struct hhf_sched_data *q)
{
	struct hh_flow_state *flow;
	u32 now = hhf_time_stamp();

	if (!list_empty(head)) {
		/* Find an expired heavy-hitter flow entry. */
		list_for_each_entry(flow, head, flowchain) {
			u32 prev = flow->hit_timestamp + q->hhf_evict_timeout;

			if (hhf_time_before(prev, now))
				return flow;
		}
	}

	if (q->hh_flows_current_cnt >= q->hh_flows_limit) {
		q->hh_flows_overlimit++;
		return NULL;
	}
	/* Create new entry. */
	flow = kzalloc(sizeof(struct hh_flow_state), GFP_ATOMIC);
	if (!flow)
		return NULL;

	q->hh_flows_current_cnt++;
	INIT_LIST_HEAD(&flow->flowchain);
	list_add_tail(&flow->flowchain, head);

	return flow;
}

/* Assigns packets to WDRR buckets.  Implements a multi-stage filter to
 * classify heavy-hitters.
 */
static enum wdrr_bucket_idx hhf_classify(struct sk_buff *skb, struct Qdisc *sch)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	u32 tmp_hash, hash;
	u32 xorsum, filter_pos[HHF_ARRAYS_CNT], flow_pos;
	struct hh_flow_state *flow;
	u32 pkt_len, min_hhf_val;
	int i;
	u32 prev;
	u32 now = hhf_time_stamp();

	/* Reset the HHF counter arrays if this is the right time. */
	prev = q->hhf_arrays_reset_timestamp + q->hhf_reset_timeout;
	if (hhf_time_before(prev, now)) {
		for (i = 0; i < HHF_ARRAYS_CNT; i++)
			bitmap_zero(q->hhf_valid_bits[i], HHF_ARRAYS_LEN);
		q->hhf_arrays_reset_timestamp = now;
	}

	/* Get hashed flow-id of the skb. */
	hash = skb_get_hash_perturb(skb, &q->perturbation);

	/* Check if this packet belongs to an already established HH flow. */
	flow_pos = hash & HHF_BIT_MASK;
	flow = seek_list(hash, &q->hh_flows[flow_pos], q);
	if (flow) { /* found its HH flow */
		flow->hit_timestamp = now;
		return WDRR_BUCKET_FOR_HH;
	}

	/* Now pass the packet through the multi-stage filter. */
	tmp_hash = hash;
	xorsum = 0;
	for (i = 0; i < HHF_ARRAYS_CNT - 1; i++) {
		/* Split the skb_hash into three 10-bit chunks. */
		filter_pos[i] = tmp_hash & HHF_BIT_MASK;
		xorsum ^= filter_pos[i];
		tmp_hash >>= HHF_BIT_MASK_LEN;
	}
	/* The last chunk is computed as XOR sum of other chunks. */
	filter_pos[HHF_ARRAYS_CNT - 1] = xorsum ^ tmp_hash;

	pkt_len = qdisc_pkt_len(skb);
	min_hhf_val = ~0U;
	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
		u32 val;

		if (!test_bit(filter_pos[i], q->hhf_valid_bits[i])) {
			q->hhf_arrays[i][filter_pos[i]] = 0;
			__set_bit(filter_pos[i], q->hhf_valid_bits[i]);
		}

		val = q->hhf_arrays[i][filter_pos[i]] + pkt_len;
		if (min_hhf_val > val)
			min_hhf_val = val;
	}

	/* Found a new HH iff all counter values > HH admit threshold. */
	if (min_hhf_val > q->hhf_admit_bytes) {
		/* Just captured a new heavy-hitter. */
		flow = alloc_new_hh(&q->hh_flows[flow_pos], q);
		if (!flow) /* memory alloc problem */
			return WDRR_BUCKET_FOR_NON_HH;
		flow->hash_id = hash;
		flow->hit_timestamp = now;
		q->hh_flows_total_cnt++;

		/* By returning without updating counters in q->hhf_arrays,
		 * we implicitly implement "shielding" (see Optimization O1).
		 */
		return WDRR_BUCKET_FOR_HH;
	}

	/* Conservative update of HHF arrays (see Optimization O2). */
	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
		if (q->hhf_arrays[i][filter_pos[i]] < min_hhf_val)
			q->hhf_arrays[i][filter_pos[i]] = min_hhf_val;
	}
	return WDRR_BUCKET_FOR_NON_HH;
}

/* Removes one skb from head of bucket. */
static struct sk_buff *dequeue_head(struct wdrr_bucket *bucket)
{
	struct sk_buff *skb = bucket->head;

	bucket->head = skb->next;
	skb_mark_not_on_list(skb);
	return skb;
}

/* Tail-adds skb to bucket. */
static void bucket_add(struct wdrr_bucket *bucket, struct sk_buff *skb)
{
	if (bucket->head == NULL)
		bucket->head = skb;
	else
		bucket->tail->next = skb;
	bucket->tail = skb;
	skb->next = NULL;
}

static unsigned int hhf_drop(struct Qdisc *sch, struct sk_buff **to_free)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	struct wdrr_bucket *bucket;

	/* Always try to drop from heavy-hitters first. */
	bucket = &q->buckets[WDRR_BUCKET_FOR_HH];
	if (!bucket->head)
		bucket = &q->buckets[WDRR_BUCKET_FOR_NON_HH];

	if (bucket->head) {
		struct sk_buff *skb = dequeue_head(bucket);

		sch->q.qlen--;
		qdisc_qstats_backlog_dec(sch, skb);
		qdisc_drop(skb, sch, to_free);
	}

	/* Return id of the bucket from which the packet was dropped. */
	return bucket - q->buckets;
}

static int hhf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
		       struct sk_buff **to_free)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	enum wdrr_bucket_idx idx;
	struct wdrr_bucket *bucket;
	unsigned int prev_backlog;

	idx = hhf_classify(skb, sch);

	bucket = &q->buckets[idx];
	bucket_add(bucket, skb);
	qdisc_qstats_backlog_inc(sch, skb);

	if (list_empty(&bucket->bucketchain)) {
		unsigned int weight;

		/* The logic of new_buckets vs. old_buckets is the same as
		 * new_flows vs. old_flows in the implementation of fq_codel,
		 * i.e., short bursts of non-HHs should have strict priority.
		 */
		if (idx == WDRR_BUCKET_FOR_HH) {
			/* Always move heavy-hitters to old bucket. */
			weight = 1;
			list_add_tail(&bucket->bucketchain, &q->old_buckets);
		} else {
			weight = q->hhf_non_hh_weight;
			list_add_tail(&bucket->bucketchain, &q->new_buckets);
		}
		bucket->deficit = weight * q->quantum;
	}
	if (++sch->q.qlen <= sch->limit)
		return NET_XMIT_SUCCESS;

	prev_backlog = sch->qstats.backlog;
	q->drop_overlimit++;
	/* Return Congestion Notification only if we dropped a packet from this
	 * bucket.
	 */
	if (hhf_drop(sch, to_free) == idx)
		return NET_XMIT_CN;

	/* As we dropped a packet, better let upper stack know this. */
	qdisc_tree_reduce_backlog(sch, 1, prev_backlog - sch->qstats.backlog);
	return NET_XMIT_SUCCESS;
}

static struct sk_buff *hhf_dequeue(struct Qdisc *sch)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	struct sk_buff *skb = NULL;
	struct wdrr_bucket *bucket;
	struct list_head *head;

begin:
	head = &q->new_buckets;
	if (list_empty(head)) {
		head = &q->old_buckets;
		if (list_empty(head))
			return NULL;
	}
	bucket = list_first_entry(head, struct wdrr_bucket, bucketchain);

	if (bucket->deficit <= 0) {
		int weight = (bucket - q->buckets == WDRR_BUCKET_FOR_HH) ?
			      1 : q->hhf_non_hh_weight;

		bucket->deficit += weight * q->quantum;
		list_move_tail(&bucket->bucketchain, &q->old_buckets);
		goto begin;
	}

	if (bucket->head) {
		skb = dequeue_head(bucket);
		sch->q.qlen--;
		qdisc_qstats_backlog_dec(sch, skb);
	}

	if (!skb) {
		/* Force a pass through old_buckets to prevent starvation. */
		if ((head == &q->new_buckets) && !list_empty(&q->old_buckets))
			list_move_tail(&bucket->bucketchain, &q->old_buckets);
		else
			list_del_init(&bucket->bucketchain);
		goto begin;
	}
	qdisc_bstats_update(sch, skb);
	bucket->deficit -= qdisc_pkt_len(skb);

	return skb;
}

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

	while ((skb = hhf_dequeue(sch)) != NULL)
		rtnl_kfree_skbs(skb, skb);
}

static void hhf_destroy(struct Qdisc *sch)
{
	int i;
	struct hhf_sched_data *q = qdisc_priv(sch);

	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
		kvfree(q->hhf_arrays[i]);
		kvfree(q->hhf_valid_bits[i]);
	}

	if (!q->hh_flows)
		return;

	for (i = 0; i < HH_FLOWS_CNT; i++) {
		struct hh_flow_state *flow, *next;
		struct list_head *head = &q->hh_flows[i];

		if (list_empty(head))
			continue;
		list_for_each_entry_safe(flow, next, head, flowchain) {
			list_del(&flow->flowchain);
			kfree(flow);
		}
	}
	kvfree(q->hh_flows);
}

static const struct nla_policy hhf_policy[TCA_HHF_MAX + 1] = {
	[TCA_HHF_BACKLOG_LIMIT]	 = { .type = NLA_U32 },
	[TCA_HHF_QUANTUM]	 = { .type = NLA_U32 },
	[TCA_HHF_HH_FLOWS_LIMIT] = { .type = NLA_U32 },
	[TCA_HHF_RESET_TIMEOUT]	 = { .type = NLA_U32 },
	[TCA_HHF_ADMIT_BYTES]	 = { .type = NLA_U32 },
	[TCA_HHF_EVICT_TIMEOUT]	 = { .type = NLA_U32 },
	[TCA_HHF_NON_HH_WEIGHT]	 = { .type = NLA_U32 },
};

static int hhf_change(struct Qdisc *sch, struct nlattr *opt,
		      struct netlink_ext_ack *extack)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	struct nlattr *tb[TCA_HHF_MAX + 1];
	unsigned int qlen, prev_backlog;
	int err;
	u64 non_hh_quantum;
	u32 new_quantum = q->quantum;
	u32 new_hhf_non_hh_weight = q->hhf_non_hh_weight;

	err = nla_parse_nested_deprecated(tb, TCA_HHF_MAX, opt, hhf_policy,
					  NULL);
	if (err < 0)
		return err;

	if (tb[TCA_HHF_QUANTUM])
		new_quantum = nla_get_u32(tb[TCA_HHF_QUANTUM]);

	if (tb[TCA_HHF_NON_HH_WEIGHT])
		new_hhf_non_hh_weight = nla_get_u32(tb[TCA_HHF_NON_HH_WEIGHT]);

	non_hh_quantum = (u64)new_quantum * new_hhf_non_hh_weight;
	if (non_hh_quantum == 0 || non_hh_quantum > INT_MAX)
		return -EINVAL;

	sch_tree_lock(sch);

	if (tb[TCA_HHF_BACKLOG_LIMIT])
		WRITE_ONCE(sch->limit, nla_get_u32(tb[TCA_HHF_BACKLOG_LIMIT]));

	WRITE_ONCE(q->quantum, new_quantum);
	WRITE_ONCE(q->hhf_non_hh_weight, new_hhf_non_hh_weight);

	if (tb[TCA_HHF_HH_FLOWS_LIMIT])
		WRITE_ONCE(q->hh_flows_limit,
			   nla_get_u32(tb[TCA_HHF_HH_FLOWS_LIMIT]));

	if (tb[TCA_HHF_RESET_TIMEOUT]) {
		u32 us = nla_get_u32(tb[TCA_HHF_RESET_TIMEOUT]);

		WRITE_ONCE(q->hhf_reset_timeout,
			   usecs_to_jiffies(us));
	}

	if (tb[TCA_HHF_ADMIT_BYTES])
		WRITE_ONCE(q->hhf_admit_bytes,
			   nla_get_u32(tb[TCA_HHF_ADMIT_BYTES]));

	if (tb[TCA_HHF_EVICT_TIMEOUT]) {
		u32 us = nla_get_u32(tb[TCA_HHF_EVICT_TIMEOUT]);

		WRITE_ONCE(q->hhf_evict_timeout,
			   usecs_to_jiffies(us));
	}

	qlen = sch->q.qlen;
	prev_backlog = sch->qstats.backlog;
	while (sch->q.qlen > sch->limit) {
		struct sk_buff *skb = hhf_dequeue(sch);

		rtnl_kfree_skbs(skb, skb);
	}
	qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen,
				  prev_backlog - sch->qstats.backlog);

	sch_tree_unlock(sch);
	return 0;
}

static int hhf_init(struct Qdisc *sch, struct nlattr *opt,
		    struct netlink_ext_ack *extack)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	int i;

	sch->limit = 1000;
	q->quantum = psched_mtu(qdisc_dev(sch));
	get_random_bytes(&q->perturbation, sizeof(q->perturbation));
	INIT_LIST_HEAD(&q->new_buckets);
	INIT_LIST_HEAD(&q->old_buckets);

	/* Configurable HHF parameters */
	q->hhf_reset_timeout = HZ / 25; /* 40  ms */
	q->hhf_admit_bytes = 131072;    /* 128 KB */
	q->hhf_evict_timeout = HZ;      /* 1  sec */
	q->hhf_non_hh_weight = 2;

	if (opt) {
		int err = hhf_change(sch, opt, extack);

		if (err)
			return err;
	}

	if (!q->hh_flows) {
		/* Initialize heavy-hitter flow table. */
		q->hh_flows = kvcalloc(HH_FLOWS_CNT, sizeof(struct list_head),
				       GFP_KERNEL);
		if (!q->hh_flows)
			return -ENOMEM;
		for (i = 0; i < HH_FLOWS_CNT; i++)
			INIT_LIST_HEAD(&q->hh_flows[i]);

		/* Cap max active HHs at twice len of hh_flows table. */
		q->hh_flows_limit = 2 * HH_FLOWS_CNT;
		q->hh_flows_overlimit = 0;
		q->hh_flows_total_cnt = 0;
		q->hh_flows_current_cnt = 0;

		/* Initialize heavy-hitter filter arrays. */
		for (i = 0; i < HHF_ARRAYS_CNT; i++) {
			q->hhf_arrays[i] = kvcalloc(HHF_ARRAYS_LEN,
						    sizeof(u32),
						    GFP_KERNEL);
			if (!q->hhf_arrays[i]) {
				/* Note: hhf_destroy() will be called
				 * by our caller.
				 */
				return -ENOMEM;
			}
		}
		q->hhf_arrays_reset_timestamp = hhf_time_stamp();

		/* Initialize valid bits of heavy-hitter filter arrays. */
		for (i = 0; i < HHF_ARRAYS_CNT; i++) {
			q->hhf_valid_bits[i] = kvzalloc(HHF_ARRAYS_LEN /
							  BITS_PER_BYTE, GFP_KERNEL);
			if (!q->hhf_valid_bits[i]) {
				/* Note: hhf_destroy() will be called
				 * by our caller.
				 */
				return -ENOMEM;
			}
		}

		/* Initialize Weighted DRR buckets. */
		for (i = 0; i < WDRR_BUCKET_CNT; i++) {
			struct wdrr_bucket *bucket = q->buckets + i;

			INIT_LIST_HEAD(&bucket->bucketchain);
		}
	}

	return 0;
}

static int hhf_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	struct nlattr *opts;

	opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
	if (opts == NULL)
		goto nla_put_failure;

	if (nla_put_u32(skb, TCA_HHF_BACKLOG_LIMIT, READ_ONCE(sch->limit)) ||
	    nla_put_u32(skb, TCA_HHF_QUANTUM, READ_ONCE(q->quantum)) ||
	    nla_put_u32(skb, TCA_HHF_HH_FLOWS_LIMIT,
			READ_ONCE(q->hh_flows_limit)) ||
	    nla_put_u32(skb, TCA_HHF_RESET_TIMEOUT,
			jiffies_to_usecs(READ_ONCE(q->hhf_reset_timeout))) ||
	    nla_put_u32(skb, TCA_HHF_ADMIT_BYTES,
			READ_ONCE(q->hhf_admit_bytes)) ||
	    nla_put_u32(skb, TCA_HHF_EVICT_TIMEOUT,
			jiffies_to_usecs(READ_ONCE(q->hhf_evict_timeout))) ||
	    nla_put_u32(skb, TCA_HHF_NON_HH_WEIGHT,
			READ_ONCE(q->hhf_non_hh_weight)))
		goto nla_put_failure;

	return nla_nest_end(skb, opts);

nla_put_failure:
	return -1;
}

static int hhf_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
	struct hhf_sched_data *q = qdisc_priv(sch);
	struct tc_hhf_xstats st = {
		.drop_overlimit = q->drop_overlimit,
		.hh_overlimit	= q->hh_flows_overlimit,
		.hh_tot_count	= q->hh_flows_total_cnt,
		.hh_cur_count	= q->hh_flows_current_cnt,
	};

	return gnet_stats_copy_app(d, &st, sizeof(st));
}

static struct Qdisc_ops hhf_qdisc_ops __read_mostly = {
	.id		=	"hhf",
	.priv_size	=	sizeof(struct hhf_sched_data),

	.enqueue	=	hhf_enqueue,
	.dequeue	=	hhf_dequeue,
	.peek		=	qdisc_peek_dequeued,
	.init		=	hhf_init,
	.reset		=	hhf_reset,
	.destroy	=	hhf_destroy,
	.change		=	hhf_change,
	.dump		=	hhf_dump,
	.dump_stats	=	hhf_dump_stats,
	.owner		=	THIS_MODULE,
};
MODULE_ALIAS_NET_SCH("hhf");

static int __init hhf_module_init(void)
{
	return register_qdisc(&hhf_qdisc_ops);
}

static void __exit hhf_module_exit(void)
{
	unregister_qdisc(&hhf_qdisc_ops);
}

module_init(hhf_module_init)
module_exit(hhf_module_exit)
MODULE_AUTHOR("Terry Lam");
MODULE_AUTHOR("Nandita Dukkipati");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Heavy-Hitter Filter (HHF)");