1 files changed, 576 insertions, 0 deletions

diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
new file mode 100644
index 000000000..c65077f0c
--- /dev/null
+++ b/net/sched/sch_pie.c
@@ -0,0 +1,576 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (C) 2013 Cisco Systems, Inc, 2013.
+ *
+ * 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:
+ * RFC 8033: https://tools.ietf.org/html/rfc8033
+ */
+
+#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>
+#include <net/pie.h>
+
+/* private data for the Qdisc */
+struct pie_sched_data {
+	struct pie_vars vars;
+	struct pie_params params;
+	struct pie_stats stats;
+	struct timer_list adapt_timer;
+	struct Qdisc *sch;
+};
+
+bool pie_drop_early(struct Qdisc *sch, struct pie_params *params,
+		    struct pie_vars *vars, u32 backlog, u32 packet_size)
+{
+	u64 rnd;
+	u64 local_prob = vars->prob;
+	u32 mtu = psched_mtu(qdisc_dev(sch));
+
+	/* If there is still burst allowance left skip random early drop */
+	if (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 ((vars->qdelay < params->target / 2) &&
+	    (vars->prob < MAX_PROB / 5))
+		return false;
+
+	/* If we have fewer than 2 mtu-sized packets, disable pie_drop_early,
+	 * similar to min_th in RED
+	 */
+	if (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 (params->bytemode && packet_size <= mtu)
+		local_prob = (u64)packet_size * div_u64(local_prob, mtu);
+	else
+		local_prob = vars->prob;
+
+	if (local_prob == 0)
+		vars->accu_prob = 0;
+	else
+		vars->accu_prob += local_prob;
+
+	if (vars->accu_prob < (MAX_PROB / 100) * 85)
+		return false;
+	if (vars->accu_prob >= (MAX_PROB / 2) * 17)
+		return true;
+
+	prandom_bytes(&rnd, 8);
+	if ((rnd >> BITS_PER_BYTE) < local_prob) {
+		vars->accu_prob = 0;
+		return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(pie_drop_early);
+
+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 (!pie_drop_early(sch, &q->params, &q->vars, sch->qstats.backlog,
+			    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) {
+		/* Set enqueue time only when dq_rate_estimator is disabled. */
+		if (!q->params.dq_rate_estimator)
+			pie_set_enqueue_time(skb);
+
+		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++;
+	q->vars.accu_prob = 0;
+	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},
+	[TCA_PIE_DQ_RATE_ESTIMATOR]	= {.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_deprecated(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]);
+
+	if (tb[TCA_PIE_DQ_RATE_ESTIMATOR])
+		q->params.dq_rate_estimator =
+				nla_get_u32(tb[TCA_PIE_DQ_RATE_ESTIMATOR]);
+
+	/* 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;
+}
+
+void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params,
+			 struct pie_vars *vars, u32 backlog)
+{
+	psched_time_t now = psched_get_time();
+	u32 dtime = 0;
+
+	/* If dq_rate_estimator is disabled, calculate qdelay using the
+	 * packet timestamp.
+	 */
+	if (!params->dq_rate_estimator) {
+		vars->qdelay = now - pie_get_enqueue_time(skb);
+
+		if (vars->dq_tstamp != DTIME_INVALID)
+			dtime = now - vars->dq_tstamp;
+
+		vars->dq_tstamp = now;
+
+		if (backlog == 0)
+			vars->qdelay = 0;
+
+		if (dtime == 0)
+			return;
+
+		goto burst_allowance_reduction;
+	}
+
+	/* 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 (backlog >= QUEUE_THRESHOLD && vars->dq_count == DQCOUNT_INVALID) {
+		vars->dq_tstamp = psched_get_time();
+		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 (vars->dq_count != DQCOUNT_INVALID) {
+		vars->dq_count += skb->len;
+
+		if (vars->dq_count >= QUEUE_THRESHOLD) {
+			u32 count = vars->dq_count << PIE_SCALE;
+
+			dtime = now - vars->dq_tstamp;
+
+			if (dtime == 0)
+				return;
+
+			count = count / dtime;
+
+			if (vars->avg_dq_rate == 0)
+				vars->avg_dq_rate = count;
+			else
+				vars->avg_dq_rate =
+				    (vars->avg_dq_rate -
+				     (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 (backlog < QUEUE_THRESHOLD) {
+				vars->dq_count = DQCOUNT_INVALID;
+			} else {
+				vars->dq_count = 0;
+				vars->dq_tstamp = psched_get_time();
+			}
+
+			goto burst_allowance_reduction;
+		}
+	}
+
+	return;
+
+burst_allowance_reduction:
+	if (vars->burst_time > 0) {
+		if (vars->burst_time > dtime)
+			vars->burst_time -= dtime;
+		else
+			vars->burst_time = 0;
+	}
+}
+EXPORT_SYMBOL_GPL(pie_process_dequeue);
+
+void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars,
+			       u32 backlog)
+{
+	psched_time_t qdelay = 0;	/* in pschedtime */
+	psched_time_t qdelay_old = 0;	/* in pschedtime */
+	s64 delta = 0;		/* determines the change in probability */
+	u64 oldprob;
+	u64 alpha, beta;
+	u32 power;
+	bool update_prob = true;
+
+	if (params->dq_rate_estimator) {
+		qdelay_old = vars->qdelay;
+		vars->qdelay_old = vars->qdelay;
+
+		if (vars->avg_dq_rate > 0)
+			qdelay = (backlog << PIE_SCALE) / vars->avg_dq_rate;
+		else
+			qdelay = 0;
+	} else {
+		qdelay = vars->qdelay;
+		qdelay_old = vars->qdelay_old;
+	}
+
+	/* If qdelay is zero and backlog is not, it means backlog is very small,
+	 * so we do not update probabilty in this round.
+	 */
+	if (qdelay == 0 && backlog != 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 scaling down
+	 * by 16 to come to 0-2 range.
+	 */
+	alpha = ((u64)params->alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+	beta = ((u64)params->beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+
+	/* We scale alpha and beta differently depending on how heavy the
+	 * congestion is. Please see RFC 8033 for details.
+	 */
+	if (vars->prob < MAX_PROB / 10) {
+		alpha >>= 1;
+		beta >>= 1;
+
+		power = 100;
+		while (vars->prob < div_u64(MAX_PROB, power) &&
+		       power <= 1000000) {
+			alpha >>= 2;
+			beta >>= 2;
+			power *= 10;
+		}
+	}
+
+	/* alpha and beta should be between 0 and 32, in multiples of 1/16 */
+	delta += alpha * (qdelay - params->target);
+	delta += beta * (qdelay - qdelay_old);
+
+	oldprob = vars->prob;
+
+	/* to ensure we increase probability in steps of no more than 2% */
+	if (delta > (s64)(MAX_PROB / (100 / 2)) &&
+	    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);
+
+	vars->prob += delta;
+
+	if (delta > 0) {
+		/* prevent overflow */
+		if (vars->prob < oldprob) {
+			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 (vars->prob > oldprob)
+			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)
+		/* Reduce drop probability to 98.4% */
+		vars->prob -= vars->prob / 64;
+
+	vars->qdelay = qdelay;
+	vars->backlog_old = backlog;
+
+	/* 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. If average dq_rate_estimator is enabled, we have atleast one
+	 *    estimate for the avg_dq_rate ie., is a non-zero value
+	 */
+	if ((vars->qdelay < params->target / 2) &&
+	    (vars->qdelay_old < params->target / 2) &&
+	    vars->prob == 0 &&
+	    (!params->dq_rate_estimator || vars->avg_dq_rate > 0)) {
+		pie_vars_init(vars);
+	}
+
+	if (!params->dq_rate_estimator)
+		vars->qdelay_old = qdelay;
+}
+EXPORT_SYMBOL_GPL(pie_calculate_probability);
+
+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);
+	pie_calculate_probability(&q->params, &q->vars, sch->qstats.backlog);
+
+	/* 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_noflag(skb, TCA_OPTIONS);
+	if (!opts)
+		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) ||
+	    nla_put_u32(skb, TCA_PIE_DQ_RATE_ESTIMATOR,
+			q->params.dq_rate_estimator))
+		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 << BITS_PER_BYTE,
+		.delay		= ((u32)PSCHED_TICKS2NS(q->vars.qdelay)) /
+				   NSEC_PER_USEC,
+		.packets_in	= q->stats.packets_in,
+		.overlimit	= q->stats.overlimit,
+		.maxq		= q->stats.maxq,
+		.dropped	= q->stats.dropped,
+		.ecn_mark	= q->stats.ecn_mark,
+	};
+
+	/* avg_dq_rate is only valid if dq_rate_estimator is enabled */
+	st.dq_rate_estimating = q->params.dq_rate_estimator;
+
+	/* unscale and return dq_rate in bytes per sec */
+	if (q->params.dq_rate_estimator)
+		st.avg_dq_rate = q->vars.avg_dq_rate *
+				 (PSCHED_TICKS_PER_SEC) >> PIE_SCALE;
+
+	return gnet_stats_copy_app(d, &st, sizeof(st));
+}
+
+static struct sk_buff *pie_qdisc_dequeue(struct Qdisc *sch)
+{
+	struct pie_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb = qdisc_dequeue_head(sch);
+
+	if (!skb)
+		return NULL;
+
+	pie_process_dequeue(skb, &q->params, &q->vars, sch->qstats.backlog);
+	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");