v4.19.13 snapshot.
diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
new file mode 100644
index 0000000..18d30bb
--- /dev/null
+++ b/net/sched/sch_pie.c
@@ -0,0 +1,572 @@
+/* Copyright (C) 2013 Cisco Systems, Inc, 2013.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Author: Vijay Subramanian <vijaynsu@cisco.com>
+ * Author: Mythili Prabhu <mysuryan@cisco.com>
+ *
+ * ECN support is added by Naeem Khademi <naeemk@ifi.uio.no>
+ * University of Oslo, Norway.
+ *
+ * References:
+ * IETF draft submission: http://tools.ietf.org/html/draft-pan-aqm-pie-00
+ * IEEE Conference on High Performance Switching and Routing 2013 :
+ * "PIE: A * Lightweight Control Scheme to Address the Bufferbloat Problem"
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/pkt_sched.h>
+#include <net/inet_ecn.h>
+
+#define QUEUE_THRESHOLD 10000
+#define DQCOUNT_INVALID -1
+#define MAX_PROB 0xffffffff
+#define PIE_SCALE 8
+
+/* parameters used */
+struct pie_params {
+ psched_time_t target; /* user specified target delay in pschedtime */
+ u32 tupdate; /* timer frequency (in jiffies) */
+ u32 limit; /* number of packets that can be enqueued */
+ u32 alpha; /* alpha and beta are between 0 and 32 */
+ u32 beta; /* and are used for shift relative to 1 */
+ bool ecn; /* true if ecn is enabled */
+ bool bytemode; /* to scale drop early prob based on pkt size */
+};
+
+/* variables used */
+struct pie_vars {
+ u32 prob; /* probability but scaled by u32 limit. */
+ psched_time_t burst_time;
+ psched_time_t qdelay;
+ psched_time_t qdelay_old;
+ u64 dq_count; /* measured in bytes */
+ psched_time_t dq_tstamp; /* drain rate */
+ u32 avg_dq_rate; /* bytes per pschedtime tick,scaled */
+ u32 qlen_old; /* in bytes */
+};
+
+/* statistics gathering */
+struct pie_stats {
+ u32 packets_in; /* total number of packets enqueued */
+ u32 dropped; /* packets dropped due to pie_action */
+ u32 overlimit; /* dropped due to lack of space in queue */
+ u32 maxq; /* maximum queue size */
+ u32 ecn_mark; /* packets marked with ECN */
+};
+
+/* private data for the Qdisc */
+struct pie_sched_data {
+ struct pie_params params;
+ struct pie_vars vars;
+ struct pie_stats stats;
+ struct timer_list adapt_timer;
+ struct Qdisc *sch;
+};
+
+static void pie_params_init(struct pie_params *params)
+{
+ params->alpha = 2;
+ params->beta = 20;
+ params->tupdate = usecs_to_jiffies(30 * USEC_PER_MSEC); /* 30 ms */
+ params->limit = 1000; /* default of 1000 packets */
+ params->target = PSCHED_NS2TICKS(20 * NSEC_PER_MSEC); /* 20 ms */
+ params->ecn = false;
+ params->bytemode = false;
+}
+
+static void pie_vars_init(struct pie_vars *vars)
+{
+ vars->dq_count = DQCOUNT_INVALID;
+ vars->avg_dq_rate = 0;
+ /* default of 100 ms in pschedtime */
+ vars->burst_time = PSCHED_NS2TICKS(100 * NSEC_PER_MSEC);
+}
+
+static bool drop_early(struct Qdisc *sch, u32 packet_size)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ u32 rnd;
+ u32 local_prob = q->vars.prob;
+ u32 mtu = psched_mtu(qdisc_dev(sch));
+
+ /* If there is still burst allowance left skip random early drop */
+ if (q->vars.burst_time > 0)
+ return false;
+
+ /* If current delay is less than half of target, and
+ * if drop prob is low already, disable early_drop
+ */
+ if ((q->vars.qdelay < q->params.target / 2)
+ && (q->vars.prob < MAX_PROB / 5))
+ return false;
+
+ /* If we have fewer than 2 mtu-sized packets, disable drop_early,
+ * similar to min_th in RED
+ */
+ if (sch->qstats.backlog < 2 * mtu)
+ return false;
+
+ /* If bytemode is turned on, use packet size to compute new
+ * probablity. Smaller packets will have lower drop prob in this case
+ */
+ if (q->params.bytemode && packet_size <= mtu)
+ local_prob = (local_prob / mtu) * packet_size;
+ else
+ local_prob = q->vars.prob;
+
+ rnd = prandom_u32();
+ if (rnd < local_prob)
+ return true;
+
+ return false;
+}
+
+static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+ struct sk_buff **to_free)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ bool enqueue = false;
+
+ if (unlikely(qdisc_qlen(sch) >= sch->limit)) {
+ q->stats.overlimit++;
+ goto out;
+ }
+
+ if (!drop_early(sch, skb->len)) {
+ enqueue = true;
+ } else if (q->params.ecn && (q->vars.prob <= MAX_PROB / 10) &&
+ INET_ECN_set_ce(skb)) {
+ /* If packet is ecn capable, mark it if drop probability
+ * is lower than 10%, else drop it.
+ */
+ q->stats.ecn_mark++;
+ enqueue = true;
+ }
+
+ /* we can enqueue the packet */
+ if (enqueue) {
+ q->stats.packets_in++;
+ if (qdisc_qlen(sch) > q->stats.maxq)
+ q->stats.maxq = qdisc_qlen(sch);
+
+ return qdisc_enqueue_tail(skb, sch);
+ }
+
+out:
+ q->stats.dropped++;
+ return qdisc_drop(skb, sch, to_free);
+}
+
+static const struct nla_policy pie_policy[TCA_PIE_MAX + 1] = {
+ [TCA_PIE_TARGET] = {.type = NLA_U32},
+ [TCA_PIE_LIMIT] = {.type = NLA_U32},
+ [TCA_PIE_TUPDATE] = {.type = NLA_U32},
+ [TCA_PIE_ALPHA] = {.type = NLA_U32},
+ [TCA_PIE_BETA] = {.type = NLA_U32},
+ [TCA_PIE_ECN] = {.type = NLA_U32},
+ [TCA_PIE_BYTEMODE] = {.type = NLA_U32},
+};
+
+static int pie_change(struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ struct nlattr *tb[TCA_PIE_MAX + 1];
+ unsigned int qlen, dropped = 0;
+ int err;
+
+ if (!opt)
+ return -EINVAL;
+
+ err = nla_parse_nested(tb, TCA_PIE_MAX, opt, pie_policy, NULL);
+ if (err < 0)
+ return err;
+
+ sch_tree_lock(sch);
+
+ /* convert from microseconds to pschedtime */
+ if (tb[TCA_PIE_TARGET]) {
+ /* target is in us */
+ u32 target = nla_get_u32(tb[TCA_PIE_TARGET]);
+
+ /* convert to pschedtime */
+ q->params.target = PSCHED_NS2TICKS((u64)target * NSEC_PER_USEC);
+ }
+
+ /* tupdate is in jiffies */
+ if (tb[TCA_PIE_TUPDATE])
+ q->params.tupdate = usecs_to_jiffies(nla_get_u32(tb[TCA_PIE_TUPDATE]));
+
+ if (tb[TCA_PIE_LIMIT]) {
+ u32 limit = nla_get_u32(tb[TCA_PIE_LIMIT]);
+
+ q->params.limit = limit;
+ sch->limit = limit;
+ }
+
+ if (tb[TCA_PIE_ALPHA])
+ q->params.alpha = nla_get_u32(tb[TCA_PIE_ALPHA]);
+
+ if (tb[TCA_PIE_BETA])
+ q->params.beta = nla_get_u32(tb[TCA_PIE_BETA]);
+
+ if (tb[TCA_PIE_ECN])
+ q->params.ecn = nla_get_u32(tb[TCA_PIE_ECN]);
+
+ if (tb[TCA_PIE_BYTEMODE])
+ q->params.bytemode = nla_get_u32(tb[TCA_PIE_BYTEMODE]);
+
+ /* Drop excess packets if new limit is lower */
+ qlen = sch->q.qlen;
+ while (sch->q.qlen > sch->limit) {
+ struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
+
+ dropped += qdisc_pkt_len(skb);
+ qdisc_qstats_backlog_dec(sch, skb);
+ rtnl_qdisc_drop(skb, sch);
+ }
+ qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
+
+ sch_tree_unlock(sch);
+ return 0;
+}
+
+static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)
+{
+
+ struct pie_sched_data *q = qdisc_priv(sch);
+ int qlen = sch->qstats.backlog; /* current queue size in bytes */
+
+ /* If current queue is about 10 packets or more and dq_count is unset
+ * we have enough packets to calculate the drain rate. Save
+ * current time as dq_tstamp and start measurement cycle.
+ */
+ if (qlen >= QUEUE_THRESHOLD && q->vars.dq_count == DQCOUNT_INVALID) {
+ q->vars.dq_tstamp = psched_get_time();
+ q->vars.dq_count = 0;
+ }
+
+ /* Calculate the average drain rate from this value. If queue length
+ * has receded to a small value viz., <= QUEUE_THRESHOLD bytes,reset
+ * the dq_count to -1 as we don't have enough packets to calculate the
+ * drain rate anymore The following if block is entered only when we
+ * have a substantial queue built up (QUEUE_THRESHOLD bytes or more)
+ * and we calculate the drain rate for the threshold here. dq_count is
+ * in bytes, time difference in psched_time, hence rate is in
+ * bytes/psched_time.
+ */
+ if (q->vars.dq_count != DQCOUNT_INVALID) {
+ q->vars.dq_count += skb->len;
+
+ if (q->vars.dq_count >= QUEUE_THRESHOLD) {
+ psched_time_t now = psched_get_time();
+ u32 dtime = now - q->vars.dq_tstamp;
+ u32 count = q->vars.dq_count << PIE_SCALE;
+
+ if (dtime == 0)
+ return;
+
+ count = count / dtime;
+
+ if (q->vars.avg_dq_rate == 0)
+ q->vars.avg_dq_rate = count;
+ else
+ q->vars.avg_dq_rate =
+ (q->vars.avg_dq_rate -
+ (q->vars.avg_dq_rate >> 3)) + (count >> 3);
+
+ /* If the queue has receded below the threshold, we hold
+ * on to the last drain rate calculated, else we reset
+ * dq_count to 0 to re-enter the if block when the next
+ * packet is dequeued
+ */
+ if (qlen < QUEUE_THRESHOLD)
+ q->vars.dq_count = DQCOUNT_INVALID;
+ else {
+ q->vars.dq_count = 0;
+ q->vars.dq_tstamp = psched_get_time();
+ }
+
+ if (q->vars.burst_time > 0) {
+ if (q->vars.burst_time > dtime)
+ q->vars.burst_time -= dtime;
+ else
+ q->vars.burst_time = 0;
+ }
+ }
+ }
+}
+
+static void calculate_probability(struct Qdisc *sch)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ u32 qlen = sch->qstats.backlog; /* queue size in bytes */
+ psched_time_t qdelay = 0; /* in pschedtime */
+ psched_time_t qdelay_old = q->vars.qdelay; /* in pschedtime */
+ s32 delta = 0; /* determines the change in probability */
+ u32 oldprob;
+ u32 alpha, beta;
+ bool update_prob = true;
+
+ q->vars.qdelay_old = q->vars.qdelay;
+
+ if (q->vars.avg_dq_rate > 0)
+ qdelay = (qlen << PIE_SCALE) / q->vars.avg_dq_rate;
+ else
+ qdelay = 0;
+
+ /* If qdelay is zero and qlen is not, it means qlen is very small, less
+ * than dequeue_rate, so we do not update probabilty in this round
+ */
+ if (qdelay == 0 && qlen != 0)
+ update_prob = false;
+
+ /* In the algorithm, alpha and beta are between 0 and 2 with typical
+ * value for alpha as 0.125. In this implementation, we use values 0-32
+ * passed from user space to represent this. Also, alpha and beta have
+ * unit of HZ and need to be scaled before they can used to update
+ * probability. alpha/beta are updated locally below by 1) scaling them
+ * appropriately 2) scaling down by 16 to come to 0-2 range.
+ * Please see paper for details.
+ *
+ * We scale alpha and beta differently depending on whether we are in
+ * light, medium or high dropping mode.
+ */
+ if (q->vars.prob < MAX_PROB / 100) {
+ alpha =
+ (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
+ beta =
+ (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
+ } else if (q->vars.prob < MAX_PROB / 10) {
+ alpha =
+ (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 5;
+ beta =
+ (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 5;
+ } else {
+ alpha =
+ (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+ beta =
+ (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+ }
+
+ /* alpha and beta should be between 0 and 32, in multiples of 1/16 */
+ delta += alpha * ((qdelay - q->params.target));
+ delta += beta * ((qdelay - qdelay_old));
+
+ oldprob = q->vars.prob;
+
+ /* to ensure we increase probability in steps of no more than 2% */
+ if (delta > (s32) (MAX_PROB / (100 / 2)) &&
+ q->vars.prob >= MAX_PROB / 10)
+ delta = (MAX_PROB / 100) * 2;
+
+ /* Non-linear drop:
+ * Tune drop probability to increase quickly for high delays(>= 250ms)
+ * 250ms is derived through experiments and provides error protection
+ */
+
+ if (qdelay > (PSCHED_NS2TICKS(250 * NSEC_PER_MSEC)))
+ delta += MAX_PROB / (100 / 2);
+
+ q->vars.prob += delta;
+
+ if (delta > 0) {
+ /* prevent overflow */
+ if (q->vars.prob < oldprob) {
+ q->vars.prob = MAX_PROB;
+ /* Prevent normalization error. If probability is at
+ * maximum value already, we normalize it here, and
+ * skip the check to do a non-linear drop in the next
+ * section.
+ */
+ update_prob = false;
+ }
+ } else {
+ /* prevent underflow */
+ if (q->vars.prob > oldprob)
+ q->vars.prob = 0;
+ }
+
+ /* Non-linear drop in probability: Reduce drop probability quickly if
+ * delay is 0 for 2 consecutive Tupdate periods.
+ */
+
+ if ((qdelay == 0) && (qdelay_old == 0) && update_prob)
+ q->vars.prob = (q->vars.prob * 98) / 100;
+
+ q->vars.qdelay = qdelay;
+ q->vars.qlen_old = qlen;
+
+ /* We restart the measurement cycle if the following conditions are met
+ * 1. If the delay has been low for 2 consecutive Tupdate periods
+ * 2. Calculated drop probability is zero
+ * 3. We have atleast one estimate for the avg_dq_rate ie.,
+ * is a non-zero value
+ */
+ if ((q->vars.qdelay < q->params.target / 2) &&
+ (q->vars.qdelay_old < q->params.target / 2) &&
+ (q->vars.prob == 0) &&
+ (q->vars.avg_dq_rate > 0))
+ pie_vars_init(&q->vars);
+}
+
+static void pie_timer(struct timer_list *t)
+{
+ struct pie_sched_data *q = from_timer(q, t, adapt_timer);
+ struct Qdisc *sch = q->sch;
+ spinlock_t *root_lock = qdisc_lock(qdisc_root_sleeping(sch));
+
+ spin_lock(root_lock);
+ calculate_probability(sch);
+
+ /* reset the timer to fire after 'tupdate'. tupdate is in jiffies. */
+ if (q->params.tupdate)
+ mod_timer(&q->adapt_timer, jiffies + q->params.tupdate);
+ spin_unlock(root_lock);
+
+}
+
+static int pie_init(struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+
+ pie_params_init(&q->params);
+ pie_vars_init(&q->vars);
+ sch->limit = q->params.limit;
+
+ q->sch = sch;
+ timer_setup(&q->adapt_timer, pie_timer, 0);
+
+ if (opt) {
+ int err = pie_change(sch, opt, extack);
+
+ if (err)
+ return err;
+ }
+
+ mod_timer(&q->adapt_timer, jiffies + HZ / 2);
+ return 0;
+}
+
+static int pie_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ struct nlattr *opts;
+
+ opts = nla_nest_start(skb, TCA_OPTIONS);
+ if (opts == NULL)
+ goto nla_put_failure;
+
+ /* convert target from pschedtime to us */
+ if (nla_put_u32(skb, TCA_PIE_TARGET,
+ ((u32) PSCHED_TICKS2NS(q->params.target)) /
+ NSEC_PER_USEC) ||
+ nla_put_u32(skb, TCA_PIE_LIMIT, sch->limit) ||
+ nla_put_u32(skb, TCA_PIE_TUPDATE, jiffies_to_usecs(q->params.tupdate)) ||
+ nla_put_u32(skb, TCA_PIE_ALPHA, q->params.alpha) ||
+ nla_put_u32(skb, TCA_PIE_BETA, q->params.beta) ||
+ nla_put_u32(skb, TCA_PIE_ECN, q->params.ecn) ||
+ nla_put_u32(skb, TCA_PIE_BYTEMODE, q->params.bytemode))
+ goto nla_put_failure;
+
+ return nla_nest_end(skb, opts);
+
+nla_put_failure:
+ nla_nest_cancel(skb, opts);
+ return -1;
+
+}
+
+static int pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ struct tc_pie_xstats st = {
+ .prob = q->vars.prob,
+ .delay = ((u32) PSCHED_TICKS2NS(q->vars.qdelay)) /
+ NSEC_PER_USEC,
+ /* unscale and return dq_rate in bytes per sec */
+ .avg_dq_rate = q->vars.avg_dq_rate *
+ (PSCHED_TICKS_PER_SEC) >> PIE_SCALE,
+ .packets_in = q->stats.packets_in,
+ .overlimit = q->stats.overlimit,
+ .maxq = q->stats.maxq,
+ .dropped = q->stats.dropped,
+ .ecn_mark = q->stats.ecn_mark,
+ };
+
+ return gnet_stats_copy_app(d, &st, sizeof(st));
+}
+
+static struct sk_buff *pie_qdisc_dequeue(struct Qdisc *sch)
+{
+ struct sk_buff *skb;
+ skb = qdisc_dequeue_head(sch);
+
+ if (!skb)
+ return NULL;
+
+ pie_process_dequeue(sch, skb);
+ return skb;
+}
+
+static void pie_reset(struct Qdisc *sch)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ qdisc_reset_queue(sch);
+ pie_vars_init(&q->vars);
+}
+
+static void pie_destroy(struct Qdisc *sch)
+{
+ struct pie_sched_data *q = qdisc_priv(sch);
+ q->params.tupdate = 0;
+ del_timer_sync(&q->adapt_timer);
+}
+
+static struct Qdisc_ops pie_qdisc_ops __read_mostly = {
+ .id = "pie",
+ .priv_size = sizeof(struct pie_sched_data),
+ .enqueue = pie_qdisc_enqueue,
+ .dequeue = pie_qdisc_dequeue,
+ .peek = qdisc_peek_dequeued,
+ .init = pie_init,
+ .destroy = pie_destroy,
+ .reset = pie_reset,
+ .change = pie_change,
+ .dump = pie_dump,
+ .dump_stats = pie_dump_stats,
+ .owner = THIS_MODULE,
+};
+
+static int __init pie_module_init(void)
+{
+ return register_qdisc(&pie_qdisc_ops);
+}
+
+static void __exit pie_module_exit(void)
+{
+ unregister_qdisc(&pie_qdisc_ops);
+}
+
+module_init(pie_module_init);
+module_exit(pie_module_exit);
+
+MODULE_DESCRIPTION("Proportional Integral controller Enhanced (PIE) scheduler");
+MODULE_AUTHOR("Vijay Subramanian");
+MODULE_AUTHOR("Mythili Prabhu");
+MODULE_LICENSE("GPL");