1 files changed, 572 insertions, 0 deletions

diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
new file mode 100644
index 000000000..18d30bb86
--- /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");