12504ba9fSThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only
2d4b36210SVijay Subramanian /* Copyright (C) 2013 Cisco Systems, Inc, 2013.
3d4b36210SVijay Subramanian *
4d4b36210SVijay Subramanian * Author: Vijay Subramanian <vijaynsu@cisco.com>
5d4b36210SVijay Subramanian * Author: Mythili Prabhu <mysuryan@cisco.com>
6d4b36210SVijay Subramanian *
7d4b36210SVijay Subramanian * ECN support is added by Naeem Khademi <naeemk@ifi.uio.no>
8d4b36210SVijay Subramanian * University of Oslo, Norway.
9219e288eSVijay Subramanian *
10219e288eSVijay Subramanian * References:
1124ed4900SLeslie Monis * RFC 8033: https://tools.ietf.org/html/rfc8033
12d4b36210SVijay Subramanian */
13d4b36210SVijay Subramanian
14d4b36210SVijay Subramanian #include <linux/module.h>
15d4b36210SVijay Subramanian #include <linux/slab.h>
16d4b36210SVijay Subramanian #include <linux/types.h>
17d4b36210SVijay Subramanian #include <linux/kernel.h>
18d4b36210SVijay Subramanian #include <linux/errno.h>
19d4b36210SVijay Subramanian #include <linux/skbuff.h>
20d4b36210SVijay Subramanian #include <net/pkt_sched.h>
21d4b36210SVijay Subramanian #include <net/inet_ecn.h>
2284bf557fSMohit P. Tahiliani #include <net/pie.h>
23d4b36210SVijay Subramanian
24d4b36210SVijay Subramanian /* private data for the Qdisc */
25d4b36210SVijay Subramanian struct pie_sched_data {
26d4b36210SVijay Subramanian struct pie_vars vars;
272dfb1952SMohit P. Tahiliani struct pie_params params;
28d4b36210SVijay Subramanian struct pie_stats stats;
29d4b36210SVijay Subramanian struct timer_list adapt_timer;
30cdeabbb8SKees Cook struct Qdisc *sch;
31d4b36210SVijay Subramanian };
32d4b36210SVijay Subramanian
pie_drop_early(struct Qdisc * sch,struct pie_params * params,struct pie_vars * vars,u32 backlog,u32 packet_size)335205ea00SMohit P. Tahiliani bool pie_drop_early(struct Qdisc *sch, struct pie_params *params,
3490baeb9dSLeslie Monis struct pie_vars *vars, u32 backlog, u32 packet_size)
35d4b36210SVijay Subramanian {
363f7ae5f3SMohit P. Tahiliani u64 rnd;
375205ea00SMohit P. Tahiliani u64 local_prob = vars->prob;
38d4b36210SVijay Subramanian u32 mtu = psched_mtu(qdisc_dev(sch));
39d4b36210SVijay Subramanian
40d4b36210SVijay Subramanian /* If there is still burst allowance left skip random early drop */
415205ea00SMohit P. Tahiliani if (vars->burst_time > 0)
42d4b36210SVijay Subramanian return false;
43d4b36210SVijay Subramanian
44d4b36210SVijay Subramanian /* If current delay is less than half of target, and
45d4b36210SVijay Subramanian * if drop prob is low already, disable early_drop
46d4b36210SVijay Subramanian */
475205ea00SMohit P. Tahiliani if ((vars->qdelay < params->target / 2) &&
485205ea00SMohit P. Tahiliani (vars->prob < MAX_PROB / 5))
49d4b36210SVijay Subramanian return false;
50d4b36210SVijay Subramanian
515205ea00SMohit P. Tahiliani /* If we have fewer than 2 mtu-sized packets, disable pie_drop_early,
52d4b36210SVijay Subramanian * similar to min_th in RED
53d4b36210SVijay Subramanian */
5490baeb9dSLeslie Monis if (backlog < 2 * mtu)
55d4b36210SVijay Subramanian return false;
56d4b36210SVijay Subramanian
57d4b36210SVijay Subramanian /* If bytemode is turned on, use packet size to compute new
58d4b36210SVijay Subramanian * probablity. Smaller packets will have lower drop prob in this case
59d4b36210SVijay Subramanian */
605205ea00SMohit P. Tahiliani if (params->bytemode && packet_size <= mtu)
613f7ae5f3SMohit P. Tahiliani local_prob = (u64)packet_size * div_u64(local_prob, mtu);
62d4b36210SVijay Subramanian else
635205ea00SMohit P. Tahiliani local_prob = vars->prob;
64d4b36210SVijay Subramanian
65105e808cSLeslie Monis if (local_prob == 0)
665205ea00SMohit P. Tahiliani vars->accu_prob = 0;
67105e808cSLeslie Monis else
685205ea00SMohit P. Tahiliani vars->accu_prob += local_prob;
6995400b97SMohit P. Tahiliani
70105e808cSLeslie Monis if (vars->accu_prob < (MAX_PROB / 100) * 85)
7195400b97SMohit P. Tahiliani return false;
72105e808cSLeslie Monis if (vars->accu_prob >= (MAX_PROB / 2) * 17)
73d4b36210SVijay Subramanian return true;
74d4b36210SVijay Subramanian
75197173dbSJason A. Donenfeld get_random_bytes(&rnd, 8);
76105e808cSLeslie Monis if ((rnd >> BITS_PER_BYTE) < local_prob) {
775205ea00SMohit P. Tahiliani vars->accu_prob = 0;
7895400b97SMohit P. Tahiliani return true;
7995400b97SMohit P. Tahiliani }
8095400b97SMohit P. Tahiliani
81d4b36210SVijay Subramanian return false;
82d4b36210SVijay Subramanian }
835205ea00SMohit P. Tahiliani EXPORT_SYMBOL_GPL(pie_drop_early);
84d4b36210SVijay Subramanian
pie_qdisc_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)85520ac30fSEric Dumazet static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
86520ac30fSEric Dumazet struct sk_buff **to_free)
87d4b36210SVijay Subramanian {
88d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
89d4b36210SVijay Subramanian bool enqueue = false;
90d4b36210SVijay Subramanian
91d4b36210SVijay Subramanian if (unlikely(qdisc_qlen(sch) >= sch->limit)) {
92d4b36210SVijay Subramanian q->stats.overlimit++;
93d4b36210SVijay Subramanian goto out;
94d4b36210SVijay Subramanian }
95d4b36210SVijay Subramanian
965205ea00SMohit P. Tahiliani if (!pie_drop_early(sch, &q->params, &q->vars, sch->qstats.backlog,
975205ea00SMohit P. Tahiliani skb->len)) {
98d4b36210SVijay Subramanian enqueue = true;
99d4b36210SVijay Subramanian } else if (q->params.ecn && (q->vars.prob <= MAX_PROB / 10) &&
100d4b36210SVijay Subramanian INET_ECN_set_ce(skb)) {
101d4b36210SVijay Subramanian /* If packet is ecn capable, mark it if drop probability
102d4b36210SVijay Subramanian * is lower than 10%, else drop it.
103d4b36210SVijay Subramanian */
104d4b36210SVijay Subramanian q->stats.ecn_mark++;
105d4b36210SVijay Subramanian enqueue = true;
106d4b36210SVijay Subramanian }
107d4b36210SVijay Subramanian
108d4b36210SVijay Subramanian /* we can enqueue the packet */
109d4b36210SVijay Subramanian if (enqueue) {
110cec2975fSGautam Ramakrishnan /* Set enqueue time only when dq_rate_estimator is disabled. */
111cec2975fSGautam Ramakrishnan if (!q->params.dq_rate_estimator)
112cec2975fSGautam Ramakrishnan pie_set_enqueue_time(skb);
113cec2975fSGautam Ramakrishnan
114d4b36210SVijay Subramanian q->stats.packets_in++;
115d4b36210SVijay Subramanian if (qdisc_qlen(sch) > q->stats.maxq)
116d4b36210SVijay Subramanian q->stats.maxq = qdisc_qlen(sch);
117d4b36210SVijay Subramanian
118d4b36210SVijay Subramanian return qdisc_enqueue_tail(skb, sch);
119d4b36210SVijay Subramanian }
120d4b36210SVijay Subramanian
121d4b36210SVijay Subramanian out:
122d4b36210SVijay Subramanian q->stats.dropped++;
12395400b97SMohit P. Tahiliani q->vars.accu_prob = 0;
124520ac30fSEric Dumazet return qdisc_drop(skb, sch, to_free);
125d4b36210SVijay Subramanian }
126d4b36210SVijay Subramanian
127d4b36210SVijay Subramanian static const struct nla_policy pie_policy[TCA_PIE_MAX + 1] = {
128d4b36210SVijay Subramanian [TCA_PIE_TARGET] = {.type = NLA_U32},
129d4b36210SVijay Subramanian [TCA_PIE_LIMIT] = {.type = NLA_U32},
130d4b36210SVijay Subramanian [TCA_PIE_TUPDATE] = {.type = NLA_U32},
131d4b36210SVijay Subramanian [TCA_PIE_ALPHA] = {.type = NLA_U32},
132d4b36210SVijay Subramanian [TCA_PIE_BETA] = {.type = NLA_U32},
133d4b36210SVijay Subramanian [TCA_PIE_ECN] = {.type = NLA_U32},
134d4b36210SVijay Subramanian [TCA_PIE_BYTEMODE] = {.type = NLA_U32},
135cec2975fSGautam Ramakrishnan [TCA_PIE_DQ_RATE_ESTIMATOR] = {.type = NLA_U32},
136d4b36210SVijay Subramanian };
137d4b36210SVijay Subramanian
pie_change(struct Qdisc * sch,struct nlattr * opt,struct netlink_ext_ack * extack)1382030721cSAlexander Aring static int pie_change(struct Qdisc *sch, struct nlattr *opt,
1392030721cSAlexander Aring struct netlink_ext_ack *extack)
140d4b36210SVijay Subramanian {
141d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
142d4b36210SVijay Subramanian struct nlattr *tb[TCA_PIE_MAX + 1];
1432ccccf5fSWANG Cong unsigned int qlen, dropped = 0;
144d4b36210SVijay Subramanian int err;
145d4b36210SVijay Subramanian
1468cb08174SJohannes Berg err = nla_parse_nested_deprecated(tb, TCA_PIE_MAX, opt, pie_policy,
1478cb08174SJohannes Berg NULL);
148d4b36210SVijay Subramanian if (err < 0)
149d4b36210SVijay Subramanian return err;
150d4b36210SVijay Subramanian
151d4b36210SVijay Subramanian sch_tree_lock(sch);
152d4b36210SVijay Subramanian
153d4b36210SVijay Subramanian /* convert from microseconds to pschedtime */
154d4b36210SVijay Subramanian if (tb[TCA_PIE_TARGET]) {
155d4b36210SVijay Subramanian /* target is in us */
156d4b36210SVijay Subramanian u32 target = nla_get_u32(tb[TCA_PIE_TARGET]);
157d4b36210SVijay Subramanian
158d4b36210SVijay Subramanian /* convert to pschedtime */
159*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.target,
160*6c00dc4fSEric Dumazet PSCHED_NS2TICKS((u64)target * NSEC_PER_USEC));
161d4b36210SVijay Subramanian }
162d4b36210SVijay Subramanian
163d4b36210SVijay Subramanian /* tupdate is in jiffies */
164d4b36210SVijay Subramanian if (tb[TCA_PIE_TUPDATE])
165*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.tupdate,
166*6c00dc4fSEric Dumazet usecs_to_jiffies(nla_get_u32(tb[TCA_PIE_TUPDATE])));
167d4b36210SVijay Subramanian
168d4b36210SVijay Subramanian if (tb[TCA_PIE_LIMIT]) {
169d4b36210SVijay Subramanian u32 limit = nla_get_u32(tb[TCA_PIE_LIMIT]);
170d4b36210SVijay Subramanian
171*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.limit, limit);
172*6c00dc4fSEric Dumazet WRITE_ONCE(sch->limit, limit);
173d4b36210SVijay Subramanian }
174d4b36210SVijay Subramanian
175d4b36210SVijay Subramanian if (tb[TCA_PIE_ALPHA])
176*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.alpha, nla_get_u32(tb[TCA_PIE_ALPHA]));
177d4b36210SVijay Subramanian
178d4b36210SVijay Subramanian if (tb[TCA_PIE_BETA])
179*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.beta, nla_get_u32(tb[TCA_PIE_BETA]));
180d4b36210SVijay Subramanian
181d4b36210SVijay Subramanian if (tb[TCA_PIE_ECN])
182*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.ecn, nla_get_u32(tb[TCA_PIE_ECN]));
183d4b36210SVijay Subramanian
184d4b36210SVijay Subramanian if (tb[TCA_PIE_BYTEMODE])
185*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.bytemode,
186*6c00dc4fSEric Dumazet nla_get_u32(tb[TCA_PIE_BYTEMODE]));
187d4b36210SVijay Subramanian
188cec2975fSGautam Ramakrishnan if (tb[TCA_PIE_DQ_RATE_ESTIMATOR])
189*6c00dc4fSEric Dumazet WRITE_ONCE(q->params.dq_rate_estimator,
190*6c00dc4fSEric Dumazet nla_get_u32(tb[TCA_PIE_DQ_RATE_ESTIMATOR]));
191cec2975fSGautam Ramakrishnan
192d4b36210SVijay Subramanian /* Drop excess packets if new limit is lower */
193d4b36210SVijay Subramanian qlen = sch->q.qlen;
194d4b36210SVijay Subramanian while (sch->q.qlen > sch->limit) {
195ed760cb8SFlorian Westphal struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
196d4b36210SVijay Subramanian
1972ccccf5fSWANG Cong dropped += qdisc_pkt_len(skb);
19825331d6cSJohn Fastabend qdisc_qstats_backlog_dec(sch, skb);
199db4879d9SEric Dumazet rtnl_qdisc_drop(skb, sch);
200d4b36210SVijay Subramanian }
2012ccccf5fSWANG Cong qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
202d4b36210SVijay Subramanian
203d4b36210SVijay Subramanian sch_tree_unlock(sch);
204d4b36210SVijay Subramanian return 0;
205d4b36210SVijay Subramanian }
206d4b36210SVijay Subramanian
pie_process_dequeue(struct sk_buff * skb,struct pie_params * params,struct pie_vars * vars,u32 backlog)2075205ea00SMohit P. Tahiliani void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params,
20890baeb9dSLeslie Monis struct pie_vars *vars, u32 backlog)
209d4b36210SVijay Subramanian {
210cec2975fSGautam Ramakrishnan psched_time_t now = psched_get_time();
211cec2975fSGautam Ramakrishnan u32 dtime = 0;
212cec2975fSGautam Ramakrishnan
213cec2975fSGautam Ramakrishnan /* If dq_rate_estimator is disabled, calculate qdelay using the
214cec2975fSGautam Ramakrishnan * packet timestamp.
215cec2975fSGautam Ramakrishnan */
2165205ea00SMohit P. Tahiliani if (!params->dq_rate_estimator) {
2175205ea00SMohit P. Tahiliani vars->qdelay = now - pie_get_enqueue_time(skb);
218cec2975fSGautam Ramakrishnan
2195205ea00SMohit P. Tahiliani if (vars->dq_tstamp != DTIME_INVALID)
2205205ea00SMohit P. Tahiliani dtime = now - vars->dq_tstamp;
221cec2975fSGautam Ramakrishnan
2225205ea00SMohit P. Tahiliani vars->dq_tstamp = now;
223cec2975fSGautam Ramakrishnan
22490baeb9dSLeslie Monis if (backlog == 0)
2255205ea00SMohit P. Tahiliani vars->qdelay = 0;
226cec2975fSGautam Ramakrishnan
227cec2975fSGautam Ramakrishnan if (dtime == 0)
228cec2975fSGautam Ramakrishnan return;
229cec2975fSGautam Ramakrishnan
230cec2975fSGautam Ramakrishnan goto burst_allowance_reduction;
231cec2975fSGautam Ramakrishnan }
232d4b36210SVijay Subramanian
233d4b36210SVijay Subramanian /* If current queue is about 10 packets or more and dq_count is unset
234d4b36210SVijay Subramanian * we have enough packets to calculate the drain rate. Save
235d4b36210SVijay Subramanian * current time as dq_tstamp and start measurement cycle.
236d4b36210SVijay Subramanian */
23790baeb9dSLeslie Monis if (backlog >= QUEUE_THRESHOLD && vars->dq_count == DQCOUNT_INVALID) {
2385205ea00SMohit P. Tahiliani vars->dq_tstamp = psched_get_time();
2395205ea00SMohit P. Tahiliani vars->dq_count = 0;
240d4b36210SVijay Subramanian }
241d4b36210SVijay Subramanian
242d4b36210SVijay Subramanian /* Calculate the average drain rate from this value. If queue length
243d4b36210SVijay Subramanian * has receded to a small value viz., <= QUEUE_THRESHOLD bytes, reset
244d4b36210SVijay Subramanian * the dq_count to -1 as we don't have enough packets to calculate the
24555f780c4SMohit P. Tahiliani * drain rate anymore. The following if block is entered only when we
246d4b36210SVijay Subramanian * have a substantial queue built up (QUEUE_THRESHOLD bytes or more)
247d4b36210SVijay Subramanian * and we calculate the drain rate for the threshold here. dq_count is
248d4b36210SVijay Subramanian * in bytes, time difference in psched_time, hence rate is in
249d4b36210SVijay Subramanian * bytes/psched_time.
250d4b36210SVijay Subramanian */
2515205ea00SMohit P. Tahiliani if (vars->dq_count != DQCOUNT_INVALID) {
2525205ea00SMohit P. Tahiliani vars->dq_count += skb->len;
253d4b36210SVijay Subramanian
2545205ea00SMohit P. Tahiliani if (vars->dq_count >= QUEUE_THRESHOLD) {
2555205ea00SMohit P. Tahiliani u32 count = vars->dq_count << PIE_SCALE;
256d4b36210SVijay Subramanian
2575205ea00SMohit P. Tahiliani dtime = now - vars->dq_tstamp;
258cec2975fSGautam Ramakrishnan
259d4b36210SVijay Subramanian if (dtime == 0)
260d4b36210SVijay Subramanian return;
261d4b36210SVijay Subramanian
262d4b36210SVijay Subramanian count = count / dtime;
263d4b36210SVijay Subramanian
2645205ea00SMohit P. Tahiliani if (vars->avg_dq_rate == 0)
2655205ea00SMohit P. Tahiliani vars->avg_dq_rate = count;
266d4b36210SVijay Subramanian else
2675205ea00SMohit P. Tahiliani vars->avg_dq_rate =
2685205ea00SMohit P. Tahiliani (vars->avg_dq_rate -
2695205ea00SMohit P. Tahiliani (vars->avg_dq_rate >> 3)) + (count >> 3);
270d4b36210SVijay Subramanian
271d4b36210SVijay Subramanian /* If the queue has receded below the threshold, we hold
272d4b36210SVijay Subramanian * on to the last drain rate calculated, else we reset
273d4b36210SVijay Subramanian * dq_count to 0 to re-enter the if block when the next
274d4b36210SVijay Subramanian * packet is dequeued
275d4b36210SVijay Subramanian */
27690baeb9dSLeslie Monis if (backlog < QUEUE_THRESHOLD) {
2775205ea00SMohit P. Tahiliani vars->dq_count = DQCOUNT_INVALID;
278ac4a02c5SLeslie Monis } else {
2795205ea00SMohit P. Tahiliani vars->dq_count = 0;
2805205ea00SMohit P. Tahiliani vars->dq_tstamp = psched_get_time();
281d4b36210SVijay Subramanian }
282d4b36210SVijay Subramanian
283cec2975fSGautam Ramakrishnan goto burst_allowance_reduction;
284cec2975fSGautam Ramakrishnan }
285cec2975fSGautam Ramakrishnan }
286cec2975fSGautam Ramakrishnan
287cec2975fSGautam Ramakrishnan return;
288cec2975fSGautam Ramakrishnan
289cec2975fSGautam Ramakrishnan burst_allowance_reduction:
2905205ea00SMohit P. Tahiliani if (vars->burst_time > 0) {
2915205ea00SMohit P. Tahiliani if (vars->burst_time > dtime)
2925205ea00SMohit P. Tahiliani vars->burst_time -= dtime;
293d4b36210SVijay Subramanian else
2945205ea00SMohit P. Tahiliani vars->burst_time = 0;
295d4b36210SVijay Subramanian }
296d4b36210SVijay Subramanian }
2975205ea00SMohit P. Tahiliani EXPORT_SYMBOL_GPL(pie_process_dequeue);
298d4b36210SVijay Subramanian
pie_calculate_probability(struct pie_params * params,struct pie_vars * vars,u32 backlog)2995205ea00SMohit P. Tahiliani void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars,
30090baeb9dSLeslie Monis u32 backlog)
301d4b36210SVijay Subramanian {
302d4b36210SVijay Subramanian psched_time_t qdelay = 0; /* in pschedtime */
303cec2975fSGautam Ramakrishnan psched_time_t qdelay_old = 0; /* in pschedtime */
3043f7ae5f3SMohit P. Tahiliani s64 delta = 0; /* determines the change in probability */
3053f7ae5f3SMohit P. Tahiliani u64 oldprob;
3063f7ae5f3SMohit P. Tahiliani u64 alpha, beta;
3073f7ae5f3SMohit P. Tahiliani u32 power;
308d4b36210SVijay Subramanian bool update_prob = true;
309d4b36210SVijay Subramanian
3105205ea00SMohit P. Tahiliani if (params->dq_rate_estimator) {
3115205ea00SMohit P. Tahiliani qdelay_old = vars->qdelay;
3125205ea00SMohit P. Tahiliani vars->qdelay_old = vars->qdelay;
313d4b36210SVijay Subramanian
3145205ea00SMohit P. Tahiliani if (vars->avg_dq_rate > 0)
31590baeb9dSLeslie Monis qdelay = (backlog << PIE_SCALE) / vars->avg_dq_rate;
316d4b36210SVijay Subramanian else
317d4b36210SVijay Subramanian qdelay = 0;
318cec2975fSGautam Ramakrishnan } else {
3195205ea00SMohit P. Tahiliani qdelay = vars->qdelay;
3205205ea00SMohit P. Tahiliani qdelay_old = vars->qdelay_old;
321cec2975fSGautam Ramakrishnan }
322d4b36210SVijay Subramanian
32390baeb9dSLeslie Monis /* If qdelay is zero and backlog is not, it means backlog is very small,
3244170f0efSTaichi Nishimura * so we do not update probability in this round.
325d4b36210SVijay Subramanian */
32690baeb9dSLeslie Monis if (qdelay == 0 && backlog != 0)
327d4b36210SVijay Subramanian update_prob = false;
328d4b36210SVijay Subramanian
329219e288eSVijay Subramanian /* In the algorithm, alpha and beta are between 0 and 2 with typical
330219e288eSVijay Subramanian * value for alpha as 0.125. In this implementation, we use values 0-32
331219e288eSVijay Subramanian * passed from user space to represent this. Also, alpha and beta have
332219e288eSVijay Subramanian * unit of HZ and need to be scaled before they can used to update
3333f7ae5f3SMohit P. Tahiliani * probability. alpha/beta are updated locally below by scaling down
3343f7ae5f3SMohit P. Tahiliani * by 16 to come to 0-2 range.
335d4b36210SVijay Subramanian */
3365205ea00SMohit P. Tahiliani alpha = ((u64)params->alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
3375205ea00SMohit P. Tahiliani beta = ((u64)params->beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
3383f7ae5f3SMohit P. Tahiliani
3393f7ae5f3SMohit P. Tahiliani /* We scale alpha and beta differently depending on how heavy the
3403f7ae5f3SMohit P. Tahiliani * congestion is. Please see RFC 8033 for details.
3413f7ae5f3SMohit P. Tahiliani */
3425205ea00SMohit P. Tahiliani if (vars->prob < MAX_PROB / 10) {
3433f7ae5f3SMohit P. Tahiliani alpha >>= 1;
3443f7ae5f3SMohit P. Tahiliani beta >>= 1;
3453f7ae5f3SMohit P. Tahiliani
3463f7ae5f3SMohit P. Tahiliani power = 100;
3475205ea00SMohit P. Tahiliani while (vars->prob < div_u64(MAX_PROB, power) &&
3483f7ae5f3SMohit P. Tahiliani power <= 1000000) {
3493f7ae5f3SMohit P. Tahiliani alpha >>= 2;
3503f7ae5f3SMohit P. Tahiliani beta >>= 2;
3513f7ae5f3SMohit P. Tahiliani power *= 10;
3523f7ae5f3SMohit P. Tahiliani }
353d4b36210SVijay Subramanian }
354d4b36210SVijay Subramanian
355d4b36210SVijay Subramanian /* alpha and beta should be between 0 and 32, in multiples of 1/16 */
356220d4ac7SLeslie Monis delta += alpha * (qdelay - params->target);
357220d4ac7SLeslie Monis delta += beta * (qdelay - qdelay_old);
358d4b36210SVijay Subramanian
3595205ea00SMohit P. Tahiliani oldprob = vars->prob;
360d4b36210SVijay Subramanian
361d4b36210SVijay Subramanian /* to ensure we increase probability in steps of no more than 2% */
3623f7ae5f3SMohit P. Tahiliani if (delta > (s64)(MAX_PROB / (100 / 2)) &&
3635205ea00SMohit P. Tahiliani vars->prob >= MAX_PROB / 10)
364d4b36210SVijay Subramanian delta = (MAX_PROB / 100) * 2;
365d4b36210SVijay Subramanian
366d4b36210SVijay Subramanian /* Non-linear drop:
367d4b36210SVijay Subramanian * Tune drop probability to increase quickly for high delays(>= 250ms)
368d4b36210SVijay Subramanian * 250ms is derived through experiments and provides error protection
369d4b36210SVijay Subramanian */
370d4b36210SVijay Subramanian
371d4b36210SVijay Subramanian if (qdelay > (PSCHED_NS2TICKS(250 * NSEC_PER_MSEC)))
372d4b36210SVijay Subramanian delta += MAX_PROB / (100 / 2);
373d4b36210SVijay Subramanian
3745205ea00SMohit P. Tahiliani vars->prob += delta;
375d4b36210SVijay Subramanian
376d4b36210SVijay Subramanian if (delta > 0) {
377d4b36210SVijay Subramanian /* prevent overflow */
3785205ea00SMohit P. Tahiliani if (vars->prob < oldprob) {
3795205ea00SMohit P. Tahiliani vars->prob = MAX_PROB;
380d4b36210SVijay Subramanian /* Prevent normalization error. If probability is at
381d4b36210SVijay Subramanian * maximum value already, we normalize it here, and
382d4b36210SVijay Subramanian * skip the check to do a non-linear drop in the next
383d4b36210SVijay Subramanian * section.
384d4b36210SVijay Subramanian */
385d4b36210SVijay Subramanian update_prob = false;
386d4b36210SVijay Subramanian }
387d4b36210SVijay Subramanian } else {
388d4b36210SVijay Subramanian /* prevent underflow */
3895205ea00SMohit P. Tahiliani if (vars->prob > oldprob)
3905205ea00SMohit P. Tahiliani vars->prob = 0;
391d4b36210SVijay Subramanian }
392d4b36210SVijay Subramanian
393d4b36210SVijay Subramanian /* Non-linear drop in probability: Reduce drop probability quickly if
394d4b36210SVijay Subramanian * delay is 0 for 2 consecutive Tupdate periods.
395d4b36210SVijay Subramanian */
396d4b36210SVijay Subramanian
397ac4a02c5SLeslie Monis if (qdelay == 0 && qdelay_old == 0 && update_prob)
3986c97da14SLeslie Monis /* Reduce drop probability to 98.4% */
3995205ea00SMohit P. Tahiliani vars->prob -= vars->prob / 64;
400d4b36210SVijay Subramanian
4015205ea00SMohit P. Tahiliani vars->qdelay = qdelay;
40290baeb9dSLeslie Monis vars->backlog_old = backlog;
403d4b36210SVijay Subramanian
404d4b36210SVijay Subramanian /* We restart the measurement cycle if the following conditions are met
405d4b36210SVijay Subramanian * 1. If the delay has been low for 2 consecutive Tupdate periods
406d4b36210SVijay Subramanian * 2. Calculated drop probability is zero
407cec2975fSGautam Ramakrishnan * 3. If average dq_rate_estimator is enabled, we have at least one
408cec2975fSGautam Ramakrishnan * estimate for the avg_dq_rate ie., is a non-zero value
409d4b36210SVijay Subramanian */
4105205ea00SMohit P. Tahiliani if ((vars->qdelay < params->target / 2) &&
4115205ea00SMohit P. Tahiliani (vars->qdelay_old < params->target / 2) &&
4125205ea00SMohit P. Tahiliani vars->prob == 0 &&
4135205ea00SMohit P. Tahiliani (!params->dq_rate_estimator || vars->avg_dq_rate > 0)) {
4145205ea00SMohit P. Tahiliani pie_vars_init(vars);
415d4b36210SVijay Subramanian }
416d4b36210SVijay Subramanian
4175205ea00SMohit P. Tahiliani if (!params->dq_rate_estimator)
4185205ea00SMohit P. Tahiliani vars->qdelay_old = qdelay;
419cec2975fSGautam Ramakrishnan }
4205205ea00SMohit P. Tahiliani EXPORT_SYMBOL_GPL(pie_calculate_probability);
421cec2975fSGautam Ramakrishnan
pie_timer(struct timer_list * t)422cdeabbb8SKees Cook static void pie_timer(struct timer_list *t)
423d4b36210SVijay Subramanian {
424cdeabbb8SKees Cook struct pie_sched_data *q = from_timer(q, t, adapt_timer);
425cdeabbb8SKees Cook struct Qdisc *sch = q->sch;
426d636fc5dSEric Dumazet spinlock_t *root_lock;
427d4b36210SVijay Subramanian
428d636fc5dSEric Dumazet rcu_read_lock();
429d636fc5dSEric Dumazet root_lock = qdisc_lock(qdisc_root_sleeping(sch));
430d4b36210SVijay Subramanian spin_lock(root_lock);
4315205ea00SMohit P. Tahiliani pie_calculate_probability(&q->params, &q->vars, sch->qstats.backlog);
432d4b36210SVijay Subramanian
433d4b36210SVijay Subramanian /* reset the timer to fire after 'tupdate'. tupdate is in jiffies. */
434d4b36210SVijay Subramanian if (q->params.tupdate)
435d4b36210SVijay Subramanian mod_timer(&q->adapt_timer, jiffies + q->params.tupdate);
436d4b36210SVijay Subramanian spin_unlock(root_lock);
437d636fc5dSEric Dumazet rcu_read_unlock();
438d4b36210SVijay Subramanian }
439d4b36210SVijay Subramanian
pie_init(struct Qdisc * sch,struct nlattr * opt,struct netlink_ext_ack * extack)440e63d7dfdSAlexander Aring static int pie_init(struct Qdisc *sch, struct nlattr *opt,
441e63d7dfdSAlexander Aring struct netlink_ext_ack *extack)
442d4b36210SVijay Subramanian {
443d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
444d4b36210SVijay Subramanian
445d4b36210SVijay Subramanian pie_params_init(&q->params);
446d4b36210SVijay Subramanian pie_vars_init(&q->vars);
447d4b36210SVijay Subramanian sch->limit = q->params.limit;
448d4b36210SVijay Subramanian
449cdeabbb8SKees Cook q->sch = sch;
450cdeabbb8SKees Cook timer_setup(&q->adapt_timer, pie_timer, 0);
451d4b36210SVijay Subramanian
452d4b36210SVijay Subramanian if (opt) {
4532030721cSAlexander Aring int err = pie_change(sch, opt, extack);
454d4b36210SVijay Subramanian
455d4b36210SVijay Subramanian if (err)
456d4b36210SVijay Subramanian return err;
457d4b36210SVijay Subramanian }
458d4b36210SVijay Subramanian
459d5610902SWANG Cong mod_timer(&q->adapt_timer, jiffies + HZ / 2);
460d4b36210SVijay Subramanian return 0;
461d4b36210SVijay Subramanian }
462d4b36210SVijay Subramanian
pie_dump(struct Qdisc * sch,struct sk_buff * skb)463d4b36210SVijay Subramanian static int pie_dump(struct Qdisc *sch, struct sk_buff *skb)
464d4b36210SVijay Subramanian {
465d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
466d4b36210SVijay Subramanian struct nlattr *opts;
467d4b36210SVijay Subramanian
468ae0be8deSMichal Kubecek opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
469ac4a02c5SLeslie Monis if (!opts)
470d4b36210SVijay Subramanian goto nla_put_failure;
471d4b36210SVijay Subramanian
472d4b36210SVijay Subramanian /* convert target from pschedtime to us */
473d4b36210SVijay Subramanian if (nla_put_u32(skb, TCA_PIE_TARGET,
474*6c00dc4fSEric Dumazet ((u32)PSCHED_TICKS2NS(READ_ONCE(q->params.target))) /
475d4b36210SVijay Subramanian NSEC_PER_USEC) ||
476*6c00dc4fSEric Dumazet nla_put_u32(skb, TCA_PIE_LIMIT, READ_ONCE(sch->limit)) ||
477ac4a02c5SLeslie Monis nla_put_u32(skb, TCA_PIE_TUPDATE,
478*6c00dc4fSEric Dumazet jiffies_to_usecs(READ_ONCE(q->params.tupdate))) ||
479*6c00dc4fSEric Dumazet nla_put_u32(skb, TCA_PIE_ALPHA, READ_ONCE(q->params.alpha)) ||
480*6c00dc4fSEric Dumazet nla_put_u32(skb, TCA_PIE_BETA, READ_ONCE(q->params.beta)) ||
481d4b36210SVijay Subramanian nla_put_u32(skb, TCA_PIE_ECN, q->params.ecn) ||
482*6c00dc4fSEric Dumazet nla_put_u32(skb, TCA_PIE_BYTEMODE,
483*6c00dc4fSEric Dumazet READ_ONCE(q->params.bytemode)) ||
484cec2975fSGautam Ramakrishnan nla_put_u32(skb, TCA_PIE_DQ_RATE_ESTIMATOR,
485*6c00dc4fSEric Dumazet READ_ONCE(q->params.dq_rate_estimator)))
486d4b36210SVijay Subramanian goto nla_put_failure;
487d4b36210SVijay Subramanian
488d4b36210SVijay Subramanian return nla_nest_end(skb, opts);
489d4b36210SVijay Subramanian
490d4b36210SVijay Subramanian nla_put_failure:
491d4b36210SVijay Subramanian nla_nest_cancel(skb, opts);
492d4b36210SVijay Subramanian return -1;
493d4b36210SVijay Subramanian }
494d4b36210SVijay Subramanian
pie_dump_stats(struct Qdisc * sch,struct gnet_dump * d)495d4b36210SVijay Subramanian static int pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
496d4b36210SVijay Subramanian {
497d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
498d4b36210SVijay Subramanian struct tc_pie_xstats st = {
4993f95f55eSLeslie Monis .prob = q->vars.prob << BITS_PER_BYTE,
500d4b36210SVijay Subramanian .delay = ((u32)PSCHED_TICKS2NS(q->vars.qdelay)) /
501d4b36210SVijay Subramanian NSEC_PER_USEC,
502d4b36210SVijay Subramanian .packets_in = q->stats.packets_in,
503d4b36210SVijay Subramanian .overlimit = q->stats.overlimit,
504d4b36210SVijay Subramanian .maxq = q->stats.maxq,
505d4b36210SVijay Subramanian .dropped = q->stats.dropped,
506d4b36210SVijay Subramanian .ecn_mark = q->stats.ecn_mark,
507d4b36210SVijay Subramanian };
508d4b36210SVijay Subramanian
509cec2975fSGautam Ramakrishnan /* avg_dq_rate is only valid if dq_rate_estimator is enabled */
510cec2975fSGautam Ramakrishnan st.dq_rate_estimating = q->params.dq_rate_estimator;
511cec2975fSGautam Ramakrishnan
512cec2975fSGautam Ramakrishnan /* unscale and return dq_rate in bytes per sec */
513cec2975fSGautam Ramakrishnan if (q->params.dq_rate_estimator)
514cec2975fSGautam Ramakrishnan st.avg_dq_rate = q->vars.avg_dq_rate *
515cec2975fSGautam Ramakrishnan (PSCHED_TICKS_PER_SEC) >> PIE_SCALE;
516cec2975fSGautam Ramakrishnan
517d4b36210SVijay Subramanian return gnet_stats_copy_app(d, &st, sizeof(st));
518d4b36210SVijay Subramanian }
519d4b36210SVijay Subramanian
pie_qdisc_dequeue(struct Qdisc * sch)520d4b36210SVijay Subramanian static struct sk_buff *pie_qdisc_dequeue(struct Qdisc *sch)
521d4b36210SVijay Subramanian {
5225205ea00SMohit P. Tahiliani struct pie_sched_data *q = qdisc_priv(sch);
523ac4a02c5SLeslie Monis struct sk_buff *skb = qdisc_dequeue_head(sch);
524d4b36210SVijay Subramanian
525d4b36210SVijay Subramanian if (!skb)
526d4b36210SVijay Subramanian return NULL;
527d4b36210SVijay Subramanian
5285205ea00SMohit P. Tahiliani pie_process_dequeue(skb, &q->params, &q->vars, sch->qstats.backlog);
529d4b36210SVijay Subramanian return skb;
530d4b36210SVijay Subramanian }
531d4b36210SVijay Subramanian
pie_reset(struct Qdisc * sch)532d4b36210SVijay Subramanian static void pie_reset(struct Qdisc *sch)
533d4b36210SVijay Subramanian {
534d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
535ac4a02c5SLeslie Monis
536d4b36210SVijay Subramanian qdisc_reset_queue(sch);
537d4b36210SVijay Subramanian pie_vars_init(&q->vars);
538d4b36210SVijay Subramanian }
539d4b36210SVijay Subramanian
pie_destroy(struct Qdisc * sch)540d4b36210SVijay Subramanian static void pie_destroy(struct Qdisc *sch)
541d4b36210SVijay Subramanian {
542d4b36210SVijay Subramanian struct pie_sched_data *q = qdisc_priv(sch);
543ac4a02c5SLeslie Monis
544d4b36210SVijay Subramanian q->params.tupdate = 0;
545d4b36210SVijay Subramanian del_timer_sync(&q->adapt_timer);
546d4b36210SVijay Subramanian }
547d4b36210SVijay Subramanian
548d4b36210SVijay Subramanian static struct Qdisc_ops pie_qdisc_ops __read_mostly = {
549d4b36210SVijay Subramanian .id = "pie",
550d4b36210SVijay Subramanian .priv_size = sizeof(struct pie_sched_data),
551d4b36210SVijay Subramanian .enqueue = pie_qdisc_enqueue,
552d4b36210SVijay Subramanian .dequeue = pie_qdisc_dequeue,
553d4b36210SVijay Subramanian .peek = qdisc_peek_dequeued,
554d4b36210SVijay Subramanian .init = pie_init,
555d4b36210SVijay Subramanian .destroy = pie_destroy,
556d4b36210SVijay Subramanian .reset = pie_reset,
557d4b36210SVijay Subramanian .change = pie_change,
558d4b36210SVijay Subramanian .dump = pie_dump,
559d4b36210SVijay Subramanian .dump_stats = pie_dump_stats,
560d4b36210SVijay Subramanian .owner = THIS_MODULE,
561d4b36210SVijay Subramanian };
562241a94abSMichal Koutný MODULE_ALIAS_NET_SCH("pie");
563d4b36210SVijay Subramanian
pie_module_init(void)564d4b36210SVijay Subramanian static int __init pie_module_init(void)
565d4b36210SVijay Subramanian {
566d4b36210SVijay Subramanian return register_qdisc(&pie_qdisc_ops);
567d4b36210SVijay Subramanian }
568d4b36210SVijay Subramanian
pie_module_exit(void)569d4b36210SVijay Subramanian static void __exit pie_module_exit(void)
570d4b36210SVijay Subramanian {
571d4b36210SVijay Subramanian unregister_qdisc(&pie_qdisc_ops);
572d4b36210SVijay Subramanian }
573d4b36210SVijay Subramanian
574d4b36210SVijay Subramanian module_init(pie_module_init);
575d4b36210SVijay Subramanian module_exit(pie_module_exit);
576d4b36210SVijay Subramanian
577d4b36210SVijay Subramanian MODULE_DESCRIPTION("Proportional Integral controller Enhanced (PIE) scheduler");
578d4b36210SVijay Subramanian MODULE_AUTHOR("Vijay Subramanian");
579d4b36210SVijay Subramanian MODULE_AUTHOR("Mythili Prabhu");
580d4b36210SVijay Subramanian MODULE_LICENSE("GPL");
581