diff options
Diffstat (limited to 'net/sched/sch_pie.c')
-rw-r--r-- | net/sched/sch_pie.c | 576 |
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"); |