2 * net/sched/sch_sfq.c Stochastic Fairness Queueing discipline.
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version
7 * 2 of the License, or (at your option) any later version.
9 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
12 #include <linux/module.h>
13 #include <linux/types.h>
14 #include <linux/kernel.h>
15 #include <linux/jiffies.h>
16 #include <linux/string.h>
18 #include <linux/errno.h>
19 #include <linux/init.h>
20 #include <linux/ipv6.h>
21 #include <linux/skbuff.h>
22 #include <linux/jhash.h>
23 #include <linux/slab.h>
24 #include <linux/vmalloc.h>
26 #include <net/netlink.h>
27 #include <net/pkt_sched.h>
30 /* Stochastic Fairness Queuing algorithm.
31 =======================================
34 Paul E. McKenney "Stochastic Fairness Queuing",
35 IEEE INFOCOMM'90 Proceedings, San Francisco, 1990.
37 Paul E. McKenney "Stochastic Fairness Queuing",
38 "Interworking: Research and Experience", v.2, 1991, p.113-131.
42 M. Shreedhar and George Varghese "Efficient Fair
43 Queuing using Deficit Round Robin", Proc. SIGCOMM 95.
46 This is not the thing that is usually called (W)FQ nowadays.
47 It does not use any timestamp mechanism, but instead
48 processes queues in round-robin order.
52 - It is very cheap. Both CPU and memory requirements are minimal.
56 - "Stochastic" -> It is not 100% fair.
57 When hash collisions occur, several flows are considered as one.
59 - "Round-robin" -> It introduces larger delays than virtual clock
60 based schemes, and should not be used for isolating interactive
61 traffic from non-interactive. It means, that this scheduler
62 should be used as leaf of CBQ or P3, which put interactive traffic
63 to higher priority band.
65 We still need true WFQ for top level CSZ, but using WFQ
66 for the best effort traffic is absolutely pointless:
67 SFQ is superior for this purpose.
70 This implementation limits maximal queue length to 128;
71 max mtu to 2^18-1; max 128 flows, number of hash buckets to 1024.
72 The only goal of this restrictions was that all data
73 fit into one 4K page on 32bit arches.
75 It is easy to increase these values, but not in flight. */
77 #define SFQ_DEPTH 128 /* max number of packets per flow */
78 #define SFQ_SLOTS 128 /* max number of flows */
79 #define SFQ_EMPTY_SLOT 255
80 #define SFQ_DEFAULT_HASH_DIVISOR 1024
82 /* We use 16 bits to store allot, and want to handle packets up to 64K
83 * Scale allot by 8 (1<<3) so that no overflow occurs.
85 #define SFQ_ALLOT_SHIFT 3
86 #define SFQ_ALLOT_SIZE(X) DIV_ROUND_UP(X, 1 << SFQ_ALLOT_SHIFT)
88 /* This type should contain at least SFQ_DEPTH + SFQ_SLOTS values */
89 typedef unsigned char sfq_index;
92 * We dont use pointers to save space.
93 * Small indexes [0 ... SFQ_SLOTS - 1] are 'pointers' to slots[] array
94 * while following values [SFQ_SLOTS ... SFQ_SLOTS + SFQ_DEPTH - 1]
95 * are 'pointers' to dep[] array
103 struct sk_buff *skblist_next;
104 struct sk_buff *skblist_prev;
105 sfq_index qlen; /* number of skbs in skblist */
106 sfq_index next; /* next slot in sfq chain */
107 struct sfq_head dep; /* anchor in dep[] chains */
108 unsigned short hash; /* hash value (index in ht[]) */
109 short allot; /* credit for this slot */
112 struct sfq_sched_data {
115 unsigned int quantum; /* Allotment per round: MUST BE >= MTU */
117 unsigned int divisor; /* number of slots in hash table */
119 struct tcf_proto *filter_list;
120 struct timer_list perturb_timer;
122 sfq_index cur_depth; /* depth of longest slot */
123 unsigned short scaled_quantum; /* SFQ_ALLOT_SIZE(quantum) */
124 struct sfq_slot *tail; /* current slot in round */
125 sfq_index *ht; /* Hash table (divisor slots) */
126 struct sfq_slot slots[SFQ_SLOTS];
127 struct sfq_head dep[SFQ_DEPTH]; /* Linked list of slots, indexed by depth */
131 * sfq_head are either in a sfq_slot or in dep[] array
133 static inline struct sfq_head *sfq_dep_head(struct sfq_sched_data *q, sfq_index val)
136 return &q->slots[val].dep;
137 return &q->dep[val - SFQ_SLOTS];
140 static unsigned int sfq_fold_hash(struct sfq_sched_data *q, u32 h, u32 h1)
142 return jhash_2words(h, h1, q->perturbation) & (q->divisor - 1);
145 static unsigned int sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb)
149 switch (skb->protocol) {
150 case htons(ETH_P_IP):
152 const struct iphdr *iph;
155 if (!pskb_network_may_pull(skb, sizeof(*iph)))
158 h = (__force u32)iph->daddr;
159 h2 = (__force u32)iph->saddr ^ iph->protocol;
160 if (iph->frag_off & htons(IP_MF | IP_OFFSET))
162 poff = proto_ports_offset(iph->protocol);
164 pskb_network_may_pull(skb, iph->ihl * 4 + 4 + poff)) {
166 h2 ^= *(u32 *)((void *)iph + iph->ihl * 4 + poff);
170 case htons(ETH_P_IPV6):
175 if (!pskb_network_may_pull(skb, sizeof(*iph)))
178 h = (__force u32)iph->daddr.s6_addr32[3];
179 h2 = (__force u32)iph->saddr.s6_addr32[3] ^ iph->nexthdr;
180 poff = proto_ports_offset(iph->nexthdr);
182 pskb_network_may_pull(skb, sizeof(*iph) + 4 + poff)) {
184 h2 ^= *(u32 *)((void *)iph + sizeof(*iph) + poff);
190 h = (unsigned long)skb_dst(skb) ^ (__force u32)skb->protocol;
191 h2 = (unsigned long)skb->sk;
194 return sfq_fold_hash(q, h, h2);
197 static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
200 struct sfq_sched_data *q = qdisc_priv(sch);
201 struct tcf_result res;
204 if (TC_H_MAJ(skb->priority) == sch->handle &&
205 TC_H_MIN(skb->priority) > 0 &&
206 TC_H_MIN(skb->priority) <= q->divisor)
207 return TC_H_MIN(skb->priority);
210 return sfq_hash(q, skb) + 1;
212 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
213 result = tc_classify(skb, q->filter_list, &res);
215 #ifdef CONFIG_NET_CLS_ACT
219 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
224 if (TC_H_MIN(res.classid) <= q->divisor)
225 return TC_H_MIN(res.classid);
231 * x : slot number [0 .. SFQ_SLOTS - 1]
233 static inline void sfq_link(struct sfq_sched_data *q, sfq_index x)
236 int qlen = q->slots[x].qlen;
238 p = qlen + SFQ_SLOTS;
239 n = q->dep[qlen].next;
241 q->slots[x].dep.next = n;
242 q->slots[x].dep.prev = p;
244 q->dep[qlen].next = x; /* sfq_dep_head(q, p)->next = x */
245 sfq_dep_head(q, n)->prev = x;
248 #define sfq_unlink(q, x, n, p) \
249 n = q->slots[x].dep.next; \
250 p = q->slots[x].dep.prev; \
251 sfq_dep_head(q, p)->next = n; \
252 sfq_dep_head(q, n)->prev = p
255 static inline void sfq_dec(struct sfq_sched_data *q, sfq_index x)
260 sfq_unlink(q, x, n, p);
262 d = q->slots[x].qlen--;
263 if (n == p && q->cur_depth == d)
268 static inline void sfq_inc(struct sfq_sched_data *q, sfq_index x)
273 sfq_unlink(q, x, n, p);
275 d = ++q->slots[x].qlen;
276 if (q->cur_depth < d)
281 /* helper functions : might be changed when/if skb use a standard list_head */
283 /* remove one skb from tail of slot queue */
284 static inline struct sk_buff *slot_dequeue_tail(struct sfq_slot *slot)
286 struct sk_buff *skb = slot->skblist_prev;
288 slot->skblist_prev = skb->prev;
289 skb->prev->next = (struct sk_buff *)slot;
290 skb->next = skb->prev = NULL;
294 /* remove one skb from head of slot queue */
295 static inline struct sk_buff *slot_dequeue_head(struct sfq_slot *slot)
297 struct sk_buff *skb = slot->skblist_next;
299 slot->skblist_next = skb->next;
300 skb->next->prev = (struct sk_buff *)slot;
301 skb->next = skb->prev = NULL;
305 static inline void slot_queue_init(struct sfq_slot *slot)
307 slot->skblist_prev = slot->skblist_next = (struct sk_buff *)slot;
310 /* add skb to slot queue (tail add) */
311 static inline void slot_queue_add(struct sfq_slot *slot, struct sk_buff *skb)
313 skb->prev = slot->skblist_prev;
314 skb->next = (struct sk_buff *)slot;
315 slot->skblist_prev->next = skb;
316 slot->skblist_prev = skb;
319 #define slot_queue_walk(slot, skb) \
320 for (skb = slot->skblist_next; \
321 skb != (struct sk_buff *)slot; \
324 static unsigned int sfq_drop(struct Qdisc *sch)
326 struct sfq_sched_data *q = qdisc_priv(sch);
327 sfq_index x, d = q->cur_depth;
330 struct sfq_slot *slot;
332 /* Queue is full! Find the longest slot and drop tail packet from it */
337 skb = slot_dequeue_tail(slot);
338 len = qdisc_pkt_len(skb);
343 sch->qstats.backlog -= len;
348 /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */
351 q->tail->next = slot->next;
352 q->ht[slot->hash] = SFQ_EMPTY_SLOT;
360 sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
362 struct sfq_sched_data *q = qdisc_priv(sch);
365 struct sfq_slot *slot;
366 int uninitialized_var(ret);
368 hash = sfq_classify(skb, sch, &ret);
370 if (ret & __NET_XMIT_BYPASS)
379 if (x == SFQ_EMPTY_SLOT) {
380 x = q->dep[0].next; /* get a free slot */
386 /* If selected queue has length q->limit, do simple tail drop,
387 * i.e. drop _this_ packet.
389 if (slot->qlen >= q->limit)
390 return qdisc_drop(skb, sch);
392 sch->qstats.backlog += qdisc_pkt_len(skb);
393 slot_queue_add(slot, skb);
395 if (slot->qlen == 1) { /* The flow is new */
396 if (q->tail == NULL) { /* It is the first flow */
399 slot->next = q->tail->next;
403 slot->allot = q->scaled_quantum;
405 if (++sch->q.qlen <= q->limit) {
406 qdisc_bstats_update(sch, skb);
407 return NET_XMIT_SUCCESS;
414 static struct sk_buff *
415 sfq_peek(struct Qdisc *sch)
417 struct sfq_sched_data *q = qdisc_priv(sch);
419 /* No active slots */
423 return q->slots[q->tail->next].skblist_next;
426 static struct sk_buff *
427 sfq_dequeue(struct Qdisc *sch)
429 struct sfq_sched_data *q = qdisc_priv(sch);
432 struct sfq_slot *slot;
434 /* No active slots */
441 if (slot->allot <= 0) {
443 slot->allot += q->scaled_quantum;
446 skb = slot_dequeue_head(slot);
449 sch->qstats.backlog -= qdisc_pkt_len(skb);
451 /* Is the slot empty? */
452 if (slot->qlen == 0) {
453 q->ht[slot->hash] = SFQ_EMPTY_SLOT;
456 q->tail = NULL; /* no more active slots */
459 q->tail->next = next_a;
461 slot->allot -= SFQ_ALLOT_SIZE(qdisc_pkt_len(skb));
467 sfq_reset(struct Qdisc *sch)
471 while ((skb = sfq_dequeue(sch)) != NULL)
475 static void sfq_perturbation(unsigned long arg)
477 struct Qdisc *sch = (struct Qdisc *)arg;
478 struct sfq_sched_data *q = qdisc_priv(sch);
480 q->perturbation = net_random();
482 if (q->perturb_period)
483 mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
486 static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
488 struct sfq_sched_data *q = qdisc_priv(sch);
489 struct tc_sfq_qopt *ctl = nla_data(opt);
492 if (opt->nla_len < nla_attr_size(sizeof(*ctl)))
496 q->quantum = ctl->quantum ? : psched_mtu(qdisc_dev(sch));
497 q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
498 q->perturb_period = ctl->perturb_period * HZ;
500 q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1);
502 if (!is_power_of_2(ctl->divisor) || ctl->divisor > 65536)
504 q->divisor = ctl->divisor;
507 while (sch->q.qlen > q->limit)
509 qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);
511 del_timer(&q->perturb_timer);
512 if (q->perturb_period) {
513 mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
514 q->perturbation = net_random();
516 sch_tree_unlock(sch);
520 static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
522 struct sfq_sched_data *q = qdisc_priv(sch);
526 q->perturb_timer.function = sfq_perturbation;
527 q->perturb_timer.data = (unsigned long)sch;
528 init_timer_deferrable(&q->perturb_timer);
530 for (i = 0; i < SFQ_DEPTH; i++) {
531 q->dep[i].next = i + SFQ_SLOTS;
532 q->dep[i].prev = i + SFQ_SLOTS;
535 q->limit = SFQ_DEPTH - 1;
538 q->divisor = SFQ_DEFAULT_HASH_DIVISOR;
540 q->quantum = psched_mtu(qdisc_dev(sch));
541 q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
542 q->perturb_period = 0;
543 q->perturbation = net_random();
545 int err = sfq_change(sch, opt);
550 sz = sizeof(q->ht[0]) * q->divisor;
551 q->ht = kmalloc(sz, GFP_KERNEL);
552 if (!q->ht && sz > PAGE_SIZE)
556 for (i = 0; i < q->divisor; i++)
557 q->ht[i] = SFQ_EMPTY_SLOT;
559 for (i = 0; i < SFQ_SLOTS; i++) {
560 slot_queue_init(&q->slots[i]);
566 static void sfq_destroy(struct Qdisc *sch)
568 struct sfq_sched_data *q = qdisc_priv(sch);
570 tcf_destroy_chain(&q->filter_list);
571 q->perturb_period = 0;
572 del_timer_sync(&q->perturb_timer);
573 if (is_vmalloc_addr(q->ht))
579 static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb)
581 struct sfq_sched_data *q = qdisc_priv(sch);
582 unsigned char *b = skb_tail_pointer(skb);
583 struct tc_sfq_qopt opt;
585 opt.quantum = q->quantum;
586 opt.perturb_period = q->perturb_period / HZ;
588 opt.limit = q->limit;
589 opt.divisor = q->divisor;
590 opt.flows = q->limit;
592 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
601 static struct Qdisc *sfq_leaf(struct Qdisc *sch, unsigned long arg)
606 static unsigned long sfq_get(struct Qdisc *sch, u32 classid)
611 static unsigned long sfq_bind(struct Qdisc *sch, unsigned long parent,
617 static void sfq_put(struct Qdisc *q, unsigned long cl)
621 static struct tcf_proto **sfq_find_tcf(struct Qdisc *sch, unsigned long cl)
623 struct sfq_sched_data *q = qdisc_priv(sch);
627 return &q->filter_list;
630 static int sfq_dump_class(struct Qdisc *sch, unsigned long cl,
631 struct sk_buff *skb, struct tcmsg *tcm)
633 tcm->tcm_handle |= TC_H_MIN(cl);
637 static int sfq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
640 struct sfq_sched_data *q = qdisc_priv(sch);
641 sfq_index idx = q->ht[cl - 1];
642 struct gnet_stats_queue qs = { 0 };
643 struct tc_sfq_xstats xstats = { 0 };
646 if (idx != SFQ_EMPTY_SLOT) {
647 const struct sfq_slot *slot = &q->slots[idx];
649 xstats.allot = slot->allot << SFQ_ALLOT_SHIFT;
650 qs.qlen = slot->qlen;
651 slot_queue_walk(slot, skb)
652 qs.backlog += qdisc_pkt_len(skb);
654 if (gnet_stats_copy_queue(d, &qs) < 0)
656 return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
659 static void sfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
661 struct sfq_sched_data *q = qdisc_priv(sch);
667 for (i = 0; i < q->divisor; i++) {
668 if (q->ht[i] == SFQ_EMPTY_SLOT ||
669 arg->count < arg->skip) {
673 if (arg->fn(sch, i + 1, arg) < 0) {
681 static const struct Qdisc_class_ops sfq_class_ops = {
685 .tcf_chain = sfq_find_tcf,
686 .bind_tcf = sfq_bind,
687 .unbind_tcf = sfq_put,
688 .dump = sfq_dump_class,
689 .dump_stats = sfq_dump_class_stats,
693 static struct Qdisc_ops sfq_qdisc_ops __read_mostly = {
694 .cl_ops = &sfq_class_ops,
696 .priv_size = sizeof(struct sfq_sched_data),
697 .enqueue = sfq_enqueue,
698 .dequeue = sfq_dequeue,
703 .destroy = sfq_destroy,
706 .owner = THIS_MODULE,
709 static int __init sfq_module_init(void)
711 return register_qdisc(&sfq_qdisc_ops);
713 static void __exit sfq_module_exit(void)
715 unregister_qdisc(&sfq_qdisc_ops);
717 module_init(sfq_module_init)
718 module_exit(sfq_module_exit)
719 MODULE_LICENSE("GPL");