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-rw-r--r--net/sched/sch_pie.c576
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 0000000000..2da6250ec3
--- /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;
+
+ get_random_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;
+
+ 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 probability 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 at least 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;
+
+ rcu_read_lock();
+ 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);
+ rcu_read_unlock();
+}
+
+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");