diff options
Diffstat (limited to 'net/sched/sch_dualpi2.c')
| -rw-r--r-- | net/sched/sch_dualpi2.c | 1175 |
1 files changed, 1175 insertions, 0 deletions
diff --git a/net/sched/sch_dualpi2.c b/net/sched/sch_dualpi2.c new file mode 100644 index 000000000000..845375ebd4ea --- /dev/null +++ b/net/sched/sch_dualpi2.c @@ -0,0 +1,1175 @@ +// SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause +/* Copyright (C) 2024 Nokia + * + * Author: Koen De Schepper <koen.de_schepper@nokia-bell-labs.com> + * Author: Olga Albisser <olga@albisser.org> + * Author: Henrik Steen <henrist@henrist.net> + * Author: Olivier Tilmans <olivier.tilmans@nokia.com> + * Author: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com> + * + * DualPI Improved with a Square (dualpi2): + * - Supports congestion controls that comply with the Prague requirements + * in RFC9331 (e.g. TCP-Prague) + * - Supports coupled dual-queue with PI2 as defined in RFC9332 + * - Supports ECN L4S-identifier (IP.ECN==0b*1) + * + * note: Although DCTCP and BBRv3 can use shallow-threshold ECN marks, + * they do not meet the 'Prague L4S Requirements' listed in RFC 9331 + * Section 4, so they can only be used with DualPI2 in a datacenter + * context. + * + * References: + * - RFC9332: https://datatracker.ietf.org/doc/html/rfc9332 + * - De Schepper, Koen, et al. "PI 2: A linearized AQM for both classic and + * scalable TCP." in proc. ACM CoNEXT'16, 2016. + */ + +#include <linux/errno.h> +#include <linux/hrtimer.h> +#include <linux/if_vlan.h> +#include <linux/kernel.h> +#include <linux/limits.h> +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/types.h> + +#include <net/gso.h> +#include <net/inet_ecn.h> +#include <net/pkt_cls.h> +#include <net/pkt_sched.h> + +/* 32b enable to support flows with windows up to ~8.6 * 1e9 packets + * i.e., twice the maximal snd_cwnd. + * MAX_PROB must be consistent with the RNG in dualpi2_roll(). + */ +#define MAX_PROB U32_MAX + +/* alpha/beta values exchanged over netlink are in units of 256ns */ +#define ALPHA_BETA_SHIFT 8 + +/* Scaled values of alpha/beta must fit in 32b to avoid overflow in later + * computations. Consequently (see and dualpi2_scale_alpha_beta()), their + * netlink-provided values can use at most 31b, i.e. be at most (2^23)-1 + * (~4MHz) as those are given in 1/256th. This enable to tune alpha/beta to + * control flows whose maximal RTTs can be in usec up to few secs. + */ +#define ALPHA_BETA_MAX ((1U << 31) - 1) + +/* Internal alpha/beta are in units of 64ns. + * This enables to use all alpha/beta values in the allowed range without loss + * of precision due to rounding when scaling them internally, e.g., + * scale_alpha_beta(1) will not round down to 0. + */ +#define ALPHA_BETA_GRANULARITY 6 + +#define ALPHA_BETA_SCALING (ALPHA_BETA_SHIFT - ALPHA_BETA_GRANULARITY) + +/* We express the weights (wc, wl) in %, i.e., wc + wl = 100 */ +#define MAX_WC 100 + +struct dualpi2_sched_data { + struct Qdisc *l_queue; /* The L4S Low latency queue (L-queue) */ + struct Qdisc *sch; /* The Classic queue (C-queue) */ + + /* Registered tc filters */ + struct tcf_proto __rcu *tcf_filters; + struct tcf_block *tcf_block; + + /* PI2 parameters */ + u64 pi2_target; /* Target delay in nanoseconds */ + u32 pi2_tupdate; /* Timer frequency in nanoseconds */ + u32 pi2_prob; /* Base PI probability */ + u32 pi2_alpha; /* Gain factor for the integral rate response */ + u32 pi2_beta; /* Gain factor for the proportional response */ + struct hrtimer pi2_timer; /* prob update timer */ + + /* Step AQM (L-queue only) parameters */ + u32 step_thresh; /* Step threshold */ + bool step_in_packets; /* Step thresh in packets (1) or time (0) */ + + /* C-queue starvation protection */ + s32 c_protection_credit; /* Credit (sign indicates which queue) */ + s32 c_protection_init; /* Reset value of the credit */ + u8 c_protection_wc; /* C-queue weight (between 0 and MAX_WC) */ + u8 c_protection_wl; /* L-queue weight (MAX_WC - wc) */ + + /* General dualQ parameters */ + u32 memory_limit; /* Memory limit of both queues */ + u8 coupling_factor;/* Coupling factor (k) between both queues */ + u8 ecn_mask; /* Mask to match packets into L-queue */ + u32 min_qlen_step; /* Minimum queue length to apply step thresh */ + bool drop_early; /* Drop at enqueue (1) instead of dequeue (0) */ + bool drop_overload; /* Drop (1) on overload, or overflow (0) */ + bool split_gso; /* Split aggregated skb (1) or leave as is (0) */ + + /* Statistics */ + u64 c_head_ts; /* Enqueue timestamp of the C-queue head */ + u64 l_head_ts; /* Enqueue timestamp of the L-queue head */ + u64 last_qdelay; /* Q delay val at the last probability update */ + u32 packets_in_c; /* Enqueue packet counter of the C-queue */ + u32 packets_in_l; /* Enqueue packet counter of the L-queue */ + u32 maxq; /* Maximum queue size of the C-queue */ + u32 ecn_mark; /* ECN mark pkt counter due to PI probability */ + u32 step_marks; /* ECN mark pkt counter due to step AQM */ + u32 memory_used; /* Memory used of both queues */ + u32 max_memory_used;/* Maximum used memory */ + + /* Deferred drop statistics */ + u32 deferred_drops_cnt; /* Packets dropped */ + u32 deferred_drops_len; /* Bytes dropped */ +}; + +struct dualpi2_skb_cb { + u64 ts; /* Timestamp at enqueue */ + u8 apply_step:1, /* Can we apply the step threshold */ + classified:2, /* Packet classification results */ + ect:2; /* Packet ECT codepoint */ +}; + +enum dualpi2_classification_results { + DUALPI2_C_CLASSIC = 0, /* C-queue */ + DUALPI2_C_L4S = 1, /* L-queue (scale mark/classic drop) */ + DUALPI2_C_LLLL = 2, /* L-queue (no drops/marks) */ + __DUALPI2_C_MAX /* Keep last*/ +}; + +static struct dualpi2_skb_cb *dualpi2_skb_cb(struct sk_buff *skb) +{ + qdisc_cb_private_validate(skb, sizeof(struct dualpi2_skb_cb)); + return (struct dualpi2_skb_cb *)qdisc_skb_cb(skb)->data; +} + +static u64 dualpi2_sojourn_time(struct sk_buff *skb, u64 reference) +{ + return reference - dualpi2_skb_cb(skb)->ts; +} + +static u64 head_enqueue_time(struct Qdisc *q) +{ + struct sk_buff *skb = qdisc_peek_head(q); + + return skb ? dualpi2_skb_cb(skb)->ts : 0; +} + +static u32 dualpi2_scale_alpha_beta(u32 param) +{ + u64 tmp = ((u64)param * MAX_PROB >> ALPHA_BETA_SCALING); + + do_div(tmp, NSEC_PER_SEC); + return tmp; +} + +static u32 dualpi2_unscale_alpha_beta(u32 param) +{ + u64 tmp = ((u64)param * NSEC_PER_SEC << ALPHA_BETA_SCALING); + + do_div(tmp, MAX_PROB); + return tmp; +} + +static ktime_t next_pi2_timeout(struct dualpi2_sched_data *q) +{ + return ktime_add_ns(ktime_get_ns(), q->pi2_tupdate); +} + +static bool skb_is_l4s(struct sk_buff *skb) +{ + return dualpi2_skb_cb(skb)->classified == DUALPI2_C_L4S; +} + +static bool skb_in_l_queue(struct sk_buff *skb) +{ + return dualpi2_skb_cb(skb)->classified != DUALPI2_C_CLASSIC; +} + +static bool skb_apply_step(struct sk_buff *skb, struct dualpi2_sched_data *q) +{ + return skb_is_l4s(skb) && qdisc_qlen(q->l_queue) >= q->min_qlen_step; +} + +static bool dualpi2_mark(struct dualpi2_sched_data *q, struct sk_buff *skb) +{ + if (INET_ECN_set_ce(skb)) { + q->ecn_mark++; + return true; + } + return false; +} + +static void dualpi2_reset_c_protection(struct dualpi2_sched_data *q) +{ + q->c_protection_credit = q->c_protection_init; +} + +/* This computes the initial credit value and WRR weight for the L queue (wl) + * from the weight of the C queue (wc). + * If wl > wc, the scheduler will start with the L queue when reset. + */ +static void dualpi2_calculate_c_protection(struct Qdisc *sch, + struct dualpi2_sched_data *q, u32 wc) +{ + q->c_protection_wc = wc; + q->c_protection_wl = MAX_WC - wc; + q->c_protection_init = (s32)psched_mtu(qdisc_dev(sch)) * + ((int)q->c_protection_wc - (int)q->c_protection_wl); + dualpi2_reset_c_protection(q); +} + +static bool dualpi2_roll(u32 prob) +{ + return get_random_u32() <= prob; +} + +/* Packets in the C-queue are subject to a marking probability pC, which is the + * square of the internal PI probability (i.e., have an overall lower mark/drop + * probability). If the qdisc is overloaded, ignore ECT values and only drop. + * + * Note that this marking scheme is also applied to L4S packets during overload. + * Return true if packet dropping is required in C queue + */ +static bool dualpi2_classic_marking(struct dualpi2_sched_data *q, + struct sk_buff *skb, u32 prob, + bool overload) +{ + if (dualpi2_roll(prob) && dualpi2_roll(prob)) { + if (overload || dualpi2_skb_cb(skb)->ect == INET_ECN_NOT_ECT) + return true; + dualpi2_mark(q, skb); + } + return false; +} + +/* Packets in the L-queue are subject to a marking probability pL given by the + * internal PI probability scaled by the coupling factor. + * + * On overload (i.e., @local_l_prob is >= 100%): + * - if the qdisc is configured to trade losses to preserve latency (i.e., + * @q->drop_overload), apply classic drops first before marking. + * - otherwise, preserve the "no loss" property of ECN at the cost of queueing + * delay, eventually resulting in taildrop behavior once sch->limit is + * reached. + * Return true if packet dropping is required in L queue + */ +static bool dualpi2_scalable_marking(struct dualpi2_sched_data *q, + struct sk_buff *skb, + u64 local_l_prob, u32 prob, + bool overload) +{ + if (overload) { + /* Apply classic drop */ + if (!q->drop_overload || + !(dualpi2_roll(prob) && dualpi2_roll(prob))) + goto mark; + return true; + } + + /* We can safely cut the upper 32b as overload==false */ + if (dualpi2_roll(local_l_prob)) { + /* Non-ECT packets could have classified as L4S by filters. */ + if (dualpi2_skb_cb(skb)->ect == INET_ECN_NOT_ECT) + return true; +mark: + dualpi2_mark(q, skb); + } + return false; +} + +/* Decide whether a given packet must be dropped (or marked if ECT), according + * to the PI2 probability. + * + * Never mark/drop if we have a standing queue of less than 2 MTUs. + */ +static bool must_drop(struct Qdisc *sch, struct dualpi2_sched_data *q, + struct sk_buff *skb) +{ + u64 local_l_prob; + bool overload; + u32 prob; + + if (sch->qstats.backlog < 2 * psched_mtu(qdisc_dev(sch))) + return false; + + prob = READ_ONCE(q->pi2_prob); + local_l_prob = (u64)prob * q->coupling_factor; + overload = local_l_prob > MAX_PROB; + + switch (dualpi2_skb_cb(skb)->classified) { + case DUALPI2_C_CLASSIC: + return dualpi2_classic_marking(q, skb, prob, overload); + case DUALPI2_C_L4S: + return dualpi2_scalable_marking(q, skb, local_l_prob, prob, + overload); + default: /* DUALPI2_C_LLLL */ + return false; + } +} + +static void dualpi2_read_ect(struct sk_buff *skb) +{ + struct dualpi2_skb_cb *cb = dualpi2_skb_cb(skb); + int wlen = skb_network_offset(skb); + + switch (skb_protocol(skb, true)) { + case htons(ETH_P_IP): + wlen += sizeof(struct iphdr); + if (!pskb_may_pull(skb, wlen) || + skb_try_make_writable(skb, wlen)) + goto not_ecn; + + cb->ect = ipv4_get_dsfield(ip_hdr(skb)) & INET_ECN_MASK; + break; + case htons(ETH_P_IPV6): + wlen += sizeof(struct ipv6hdr); + if (!pskb_may_pull(skb, wlen) || + skb_try_make_writable(skb, wlen)) + goto not_ecn; + + cb->ect = ipv6_get_dsfield(ipv6_hdr(skb)) & INET_ECN_MASK; + break; + default: + goto not_ecn; + } + return; + +not_ecn: + /* Non pullable/writable packets can only be dropped hence are + * classified as not ECT. + */ + cb->ect = INET_ECN_NOT_ECT; +} + +static int dualpi2_skb_classify(struct dualpi2_sched_data *q, + struct sk_buff *skb) +{ + struct dualpi2_skb_cb *cb = dualpi2_skb_cb(skb); + struct tcf_result res; + struct tcf_proto *fl; + int result; + + dualpi2_read_ect(skb); + if (cb->ect & q->ecn_mask) { + cb->classified = DUALPI2_C_L4S; + return NET_XMIT_SUCCESS; + } + + if (TC_H_MAJ(skb->priority) == q->sch->handle && + TC_H_MIN(skb->priority) < __DUALPI2_C_MAX) { + cb->classified = TC_H_MIN(skb->priority); + return NET_XMIT_SUCCESS; + } + + fl = rcu_dereference_bh(q->tcf_filters); + if (!fl) { + cb->classified = DUALPI2_C_CLASSIC; + return NET_XMIT_SUCCESS; + } + + result = tcf_classify(skb, NULL, fl, &res, false); + if (result >= 0) { +#ifdef CONFIG_NET_CLS_ACT + switch (result) { + case TC_ACT_STOLEN: + case TC_ACT_QUEUED: + case TC_ACT_TRAP: + return NET_XMIT_SUCCESS | __NET_XMIT_STOLEN; + case TC_ACT_SHOT: + return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; + } +#endif + cb->classified = TC_H_MIN(res.classid) < __DUALPI2_C_MAX ? + TC_H_MIN(res.classid) : DUALPI2_C_CLASSIC; + } + return NET_XMIT_SUCCESS; +} + +static int dualpi2_enqueue_skb(struct sk_buff *skb, struct Qdisc *sch, + struct sk_buff **to_free) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + struct dualpi2_skb_cb *cb; + + if (unlikely(qdisc_qlen(sch) >= sch->limit) || + unlikely((u64)q->memory_used + skb->truesize > q->memory_limit)) { + qdisc_qstats_overlimit(sch); + if (skb_in_l_queue(skb)) + qdisc_qstats_overlimit(q->l_queue); + return qdisc_drop_reason(skb, sch, to_free, + SKB_DROP_REASON_QDISC_OVERLIMIT); + } + + if (q->drop_early && must_drop(sch, q, skb)) { + qdisc_drop_reason(skb, sch, to_free, + SKB_DROP_REASON_QDISC_CONGESTED); + return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; + } + + cb = dualpi2_skb_cb(skb); + cb->ts = ktime_get_ns(); + q->memory_used += skb->truesize; + if (q->memory_used > q->max_memory_used) + q->max_memory_used = q->memory_used; + + if (qdisc_qlen(sch) > q->maxq) + q->maxq = qdisc_qlen(sch); + + if (skb_in_l_queue(skb)) { + /* Apply step thresh if skb is L4S && L-queue len >= min_qlen */ + dualpi2_skb_cb(skb)->apply_step = skb_apply_step(skb, q); + + /* Keep the overall qdisc stats consistent */ + ++sch->q.qlen; + qdisc_qstats_backlog_inc(sch, skb); + ++q->packets_in_l; + if (!q->l_head_ts) + q->l_head_ts = cb->ts; + return qdisc_enqueue_tail(skb, q->l_queue); + } + ++q->packets_in_c; + if (!q->c_head_ts) + q->c_head_ts = cb->ts; + return qdisc_enqueue_tail(skb, sch); +} + +/* By default, dualpi2 will split GSO skbs into independent skbs and enqueue + * each of those individually. This yields the following benefits, at the + * expense of CPU usage: + * - Finer-grained AQM actions as the sub-packets of a burst no longer share the + * same fate (e.g., the random mark/drop probability is applied individually) + * - Improved precision of the starvation protection/WRR scheduler at dequeue, + * as the size of the dequeued packets will be smaller. + */ +static int dualpi2_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, + struct sk_buff **to_free) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + int err; + + err = dualpi2_skb_classify(q, skb); + if (err != NET_XMIT_SUCCESS) { + if (err & __NET_XMIT_BYPASS) + qdisc_qstats_drop(sch); + __qdisc_drop(skb, to_free); + return err; + } + + if (q->split_gso && skb_is_gso(skb)) { + netdev_features_t features; + struct sk_buff *nskb, *next; + int cnt, byte_len, orig_len; + int err; + + features = netif_skb_features(skb); + nskb = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK); + if (IS_ERR_OR_NULL(nskb)) + return qdisc_drop(skb, sch, to_free); + + cnt = 1; + byte_len = 0; + orig_len = qdisc_pkt_len(skb); + skb_list_walk_safe(nskb, nskb, next) { + skb_mark_not_on_list(nskb); + + /* Iterate through GSO fragments of an skb: + * (1) Set pkt_len from the single GSO fragments + * (2) Copy classified and ect values of an skb + * (3) Enqueue fragment & set ts in dualpi2_enqueue_skb + */ + qdisc_skb_cb(nskb)->pkt_len = nskb->len; + dualpi2_skb_cb(nskb)->classified = + dualpi2_skb_cb(skb)->classified; + dualpi2_skb_cb(nskb)->ect = dualpi2_skb_cb(skb)->ect; + err = dualpi2_enqueue_skb(nskb, sch, to_free); + + if (err == NET_XMIT_SUCCESS) { + /* Compute the backlog adjustment that needs + * to be propagated in the qdisc tree to reflect + * all new skbs successfully enqueued. + */ + ++cnt; + byte_len += nskb->len; + } + } + if (cnt > 1) { + /* The caller will add the original skb stats to its + * backlog, compensate this if any nskb is enqueued. + */ + --cnt; + byte_len -= orig_len; + } + qdisc_tree_reduce_backlog(sch, -cnt, -byte_len); + consume_skb(skb); + return err; + } + return dualpi2_enqueue_skb(skb, sch, to_free); +} + +/* Select the queue from which the next packet can be dequeued, ensuring that + * neither queue can starve the other with a WRR scheduler. + * + * The sign of the WRR credit determines the next queue, while the size of + * the dequeued packet determines the magnitude of the WRR credit change. If + * either queue is empty, the WRR credit is kept unchanged. + * + * As the dequeued packet can be dropped later, the caller has to perform the + * qdisc_bstats_update() calls. + */ +static struct sk_buff *dequeue_packet(struct Qdisc *sch, + struct dualpi2_sched_data *q, + int *credit_change, + u64 now) +{ + struct sk_buff *skb = NULL; + int c_len; + + *credit_change = 0; + c_len = qdisc_qlen(sch) - qdisc_qlen(q->l_queue); + if (qdisc_qlen(q->l_queue) && (!c_len || q->c_protection_credit <= 0)) { + skb = __qdisc_dequeue_head(&q->l_queue->q); + WRITE_ONCE(q->l_head_ts, head_enqueue_time(q->l_queue)); + if (c_len) + *credit_change = q->c_protection_wc; + qdisc_qstats_backlog_dec(q->l_queue, skb); + + /* Keep the global queue size consistent */ + --sch->q.qlen; + q->memory_used -= skb->truesize; + } else if (c_len) { + skb = __qdisc_dequeue_head(&sch->q); + WRITE_ONCE(q->c_head_ts, head_enqueue_time(sch)); + if (qdisc_qlen(q->l_queue)) + *credit_change = ~((s32)q->c_protection_wl) + 1; + q->memory_used -= skb->truesize; + } else { + dualpi2_reset_c_protection(q); + return NULL; + } + *credit_change *= qdisc_pkt_len(skb); + qdisc_qstats_backlog_dec(sch, skb); + return skb; +} + +static int do_step_aqm(struct dualpi2_sched_data *q, struct sk_buff *skb, + u64 now) +{ + u64 qdelay = 0; + + if (q->step_in_packets) + qdelay = qdisc_qlen(q->l_queue); + else + qdelay = dualpi2_sojourn_time(skb, now); + + if (dualpi2_skb_cb(skb)->apply_step && qdelay > q->step_thresh) { + if (!dualpi2_skb_cb(skb)->ect) { + /* Drop this non-ECT packet */ + return 1; + } + + if (dualpi2_mark(q, skb)) + ++q->step_marks; + } + qdisc_bstats_update(q->l_queue, skb); + return 0; +} + +static void drop_and_retry(struct dualpi2_sched_data *q, struct sk_buff *skb, + struct Qdisc *sch, enum skb_drop_reason reason) +{ + ++q->deferred_drops_cnt; + q->deferred_drops_len += qdisc_pkt_len(skb); + kfree_skb_reason(skb, reason); + qdisc_qstats_drop(sch); +} + +static struct sk_buff *dualpi2_qdisc_dequeue(struct Qdisc *sch) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + struct sk_buff *skb; + int credit_change; + u64 now; + + now = ktime_get_ns(); + + while ((skb = dequeue_packet(sch, q, &credit_change, now))) { + if (!q->drop_early && must_drop(sch, q, skb)) { + drop_and_retry(q, skb, sch, + SKB_DROP_REASON_QDISC_CONGESTED); + continue; + } + + if (skb_in_l_queue(skb) && do_step_aqm(q, skb, now)) { + qdisc_qstats_drop(q->l_queue); + drop_and_retry(q, skb, sch, + SKB_DROP_REASON_DUALPI2_STEP_DROP); + continue; + } + + q->c_protection_credit += credit_change; + qdisc_bstats_update(sch, skb); + break; + } + + if (q->deferred_drops_cnt) { + qdisc_tree_reduce_backlog(sch, q->deferred_drops_cnt, + q->deferred_drops_len); + q->deferred_drops_cnt = 0; + q->deferred_drops_len = 0; + } + return skb; +} + +static s64 __scale_delta(u64 diff) +{ + do_div(diff, 1 << ALPHA_BETA_GRANULARITY); + return diff; +} + +static void get_queue_delays(struct dualpi2_sched_data *q, u64 *qdelay_c, + u64 *qdelay_l) +{ + u64 now, qc, ql; + + now = ktime_get_ns(); + qc = READ_ONCE(q->c_head_ts); + ql = READ_ONCE(q->l_head_ts); + + *qdelay_c = qc ? now - qc : 0; + *qdelay_l = ql ? now - ql : 0; +} + +static u32 calculate_probability(struct Qdisc *sch) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + u32 new_prob; + u64 qdelay_c; + u64 qdelay_l; + u64 qdelay; + s64 delta; + + get_queue_delays(q, &qdelay_c, &qdelay_l); + qdelay = max(qdelay_l, qdelay_c); + + /* Alpha and beta take at most 32b, i.e, the delay difference would + * overflow for queuing delay differences > ~4.2sec. + */ + delta = ((s64)qdelay - (s64)q->pi2_target) * q->pi2_alpha; + delta += ((s64)qdelay - (s64)q->last_qdelay) * q->pi2_beta; + q->last_qdelay = qdelay; + + /* Bound new_prob between 0 and MAX_PROB */ + if (delta > 0) { + new_prob = __scale_delta(delta) + q->pi2_prob; + if (new_prob < q->pi2_prob) + new_prob = MAX_PROB; + } else { + new_prob = q->pi2_prob - __scale_delta(~delta + 1); + if (new_prob > q->pi2_prob) + new_prob = 0; + } + + /* If we do not drop on overload, ensure we cap the L4S probability to + * 100% to keep window fairness when overflowing. + */ + if (!q->drop_overload) + return min_t(u32, new_prob, MAX_PROB / q->coupling_factor); + return new_prob; +} + +static u32 get_memory_limit(struct Qdisc *sch, u32 limit) +{ + /* Apply rule of thumb, i.e., doubling the packet length, + * to further include per packet overhead in memory_limit. + */ + u64 memlim = mul_u32_u32(limit, 2 * psched_mtu(qdisc_dev(sch))); + + if (upper_32_bits(memlim)) + return U32_MAX; + else + return lower_32_bits(memlim); +} + +static u32 convert_us_to_nsec(u32 us) +{ + u64 ns = mul_u32_u32(us, NSEC_PER_USEC); + + if (upper_32_bits(ns)) + return U32_MAX; + + return lower_32_bits(ns); +} + +static u32 convert_ns_to_usec(u64 ns) +{ + do_div(ns, NSEC_PER_USEC); + if (upper_32_bits(ns)) + return U32_MAX; + + return lower_32_bits(ns); +} + +static enum hrtimer_restart dualpi2_timer(struct hrtimer *timer) +{ + struct dualpi2_sched_data *q = timer_container_of(q, timer, pi2_timer); + struct Qdisc *sch = q->sch; + spinlock_t *root_lock; /* to lock qdisc for probability calculations */ + + rcu_read_lock(); + root_lock = qdisc_lock(qdisc_root_sleeping(sch)); + spin_lock(root_lock); + + WRITE_ONCE(q->pi2_prob, calculate_probability(sch)); + hrtimer_set_expires(&q->pi2_timer, next_pi2_timeout(q)); + + spin_unlock(root_lock); + rcu_read_unlock(); + return HRTIMER_RESTART; +} + +static struct netlink_range_validation dualpi2_alpha_beta_range = { + .min = 1, + .max = ALPHA_BETA_MAX, +}; + +static const struct nla_policy dualpi2_policy[TCA_DUALPI2_MAX + 1] = { + [TCA_DUALPI2_LIMIT] = NLA_POLICY_MIN(NLA_U32, 1), + [TCA_DUALPI2_MEMORY_LIMIT] = NLA_POLICY_MIN(NLA_U32, 1), + [TCA_DUALPI2_TARGET] = { .type = NLA_U32 }, + [TCA_DUALPI2_TUPDATE] = NLA_POLICY_MIN(NLA_U32, 1), + [TCA_DUALPI2_ALPHA] = + NLA_POLICY_FULL_RANGE(NLA_U32, &dualpi2_alpha_beta_range), + [TCA_DUALPI2_BETA] = + NLA_POLICY_FULL_RANGE(NLA_U32, &dualpi2_alpha_beta_range), + [TCA_DUALPI2_STEP_THRESH_PKTS] = { .type = NLA_U32 }, + [TCA_DUALPI2_STEP_THRESH_US] = { .type = NLA_U32 }, + [TCA_DUALPI2_MIN_QLEN_STEP] = { .type = NLA_U32 }, + [TCA_DUALPI2_COUPLING] = NLA_POLICY_MIN(NLA_U8, 1), + [TCA_DUALPI2_DROP_OVERLOAD] = + NLA_POLICY_MAX(NLA_U8, TCA_DUALPI2_DROP_OVERLOAD_MAX), + [TCA_DUALPI2_DROP_EARLY] = + NLA_POLICY_MAX(NLA_U8, TCA_DUALPI2_DROP_EARLY_MAX), + [TCA_DUALPI2_C_PROTECTION] = + NLA_POLICY_RANGE(NLA_U8, 0, MAX_WC), + [TCA_DUALPI2_ECN_MASK] = + NLA_POLICY_RANGE(NLA_U8, TC_DUALPI2_ECN_MASK_L4S_ECT, + TCA_DUALPI2_ECN_MASK_MAX), + [TCA_DUALPI2_SPLIT_GSO] = + NLA_POLICY_MAX(NLA_U8, TCA_DUALPI2_SPLIT_GSO_MAX), +}; + +static int dualpi2_change(struct Qdisc *sch, struct nlattr *opt, + struct netlink_ext_ack *extack) +{ + struct nlattr *tb[TCA_DUALPI2_MAX + 1]; + struct dualpi2_sched_data *q; + int old_backlog; + int old_qlen; + int err; + + if (!opt || !nla_len(opt)) { + NL_SET_ERR_MSG_MOD(extack, "Dualpi2 options are required"); + return -EINVAL; + } + err = nla_parse_nested(tb, TCA_DUALPI2_MAX, opt, dualpi2_policy, + extack); + if (err < 0) + return err; + if (tb[TCA_DUALPI2_STEP_THRESH_PKTS] && tb[TCA_DUALPI2_STEP_THRESH_US]) { + NL_SET_ERR_MSG_MOD(extack, "multiple step thresh attributes"); + return -EINVAL; + } + + q = qdisc_priv(sch); + sch_tree_lock(sch); + + if (tb[TCA_DUALPI2_LIMIT]) { + u32 limit = nla_get_u32(tb[TCA_DUALPI2_LIMIT]); + + WRITE_ONCE(sch->limit, limit); + WRITE_ONCE(q->memory_limit, get_memory_limit(sch, limit)); + } + + if (tb[TCA_DUALPI2_MEMORY_LIMIT]) + WRITE_ONCE(q->memory_limit, + nla_get_u32(tb[TCA_DUALPI2_MEMORY_LIMIT])); + + if (tb[TCA_DUALPI2_TARGET]) { + u64 target = nla_get_u32(tb[TCA_DUALPI2_TARGET]); + + WRITE_ONCE(q->pi2_target, target * NSEC_PER_USEC); + } + + if (tb[TCA_DUALPI2_TUPDATE]) { + u64 tupdate = nla_get_u32(tb[TCA_DUALPI2_TUPDATE]); + + WRITE_ONCE(q->pi2_tupdate, convert_us_to_nsec(tupdate)); + } + + if (tb[TCA_DUALPI2_ALPHA]) { + u32 alpha = nla_get_u32(tb[TCA_DUALPI2_ALPHA]); + + WRITE_ONCE(q->pi2_alpha, dualpi2_scale_alpha_beta(alpha)); + } + + if (tb[TCA_DUALPI2_BETA]) { + u32 beta = nla_get_u32(tb[TCA_DUALPI2_BETA]); + + WRITE_ONCE(q->pi2_beta, dualpi2_scale_alpha_beta(beta)); + } + + if (tb[TCA_DUALPI2_STEP_THRESH_PKTS]) { + u32 step_th = nla_get_u32(tb[TCA_DUALPI2_STEP_THRESH_PKTS]); + + WRITE_ONCE(q->step_in_packets, true); + WRITE_ONCE(q->step_thresh, step_th); + } else if (tb[TCA_DUALPI2_STEP_THRESH_US]) { + u32 step_th = nla_get_u32(tb[TCA_DUALPI2_STEP_THRESH_US]); + + WRITE_ONCE(q->step_in_packets, false); + WRITE_ONCE(q->step_thresh, convert_us_to_nsec(step_th)); + } + + if (tb[TCA_DUALPI2_MIN_QLEN_STEP]) + WRITE_ONCE(q->min_qlen_step, + nla_get_u32(tb[TCA_DUALPI2_MIN_QLEN_STEP])); + + if (tb[TCA_DUALPI2_COUPLING]) { + u8 coupling = nla_get_u8(tb[TCA_DUALPI2_COUPLING]); + + WRITE_ONCE(q->coupling_factor, coupling); + } + + if (tb[TCA_DUALPI2_DROP_OVERLOAD]) { + u8 drop_overload = nla_get_u8(tb[TCA_DUALPI2_DROP_OVERLOAD]); + + WRITE_ONCE(q->drop_overload, (bool)drop_overload); + } + + if (tb[TCA_DUALPI2_DROP_EARLY]) { + u8 drop_early = nla_get_u8(tb[TCA_DUALPI2_DROP_EARLY]); + + WRITE_ONCE(q->drop_early, (bool)drop_early); + } + + if (tb[TCA_DUALPI2_C_PROTECTION]) { + u8 wc = nla_get_u8(tb[TCA_DUALPI2_C_PROTECTION]); + + dualpi2_calculate_c_protection(sch, q, wc); + } + + if (tb[TCA_DUALPI2_ECN_MASK]) { + u8 ecn_mask = nla_get_u8(tb[TCA_DUALPI2_ECN_MASK]); + + WRITE_ONCE(q->ecn_mask, ecn_mask); + } + + if (tb[TCA_DUALPI2_SPLIT_GSO]) { + u8 split_gso = nla_get_u8(tb[TCA_DUALPI2_SPLIT_GSO]); + + WRITE_ONCE(q->split_gso, (bool)split_gso); + } + + old_qlen = qdisc_qlen(sch); + old_backlog = sch->qstats.backlog; + while (qdisc_qlen(sch) > sch->limit || + q->memory_used > q->memory_limit) { + struct sk_buff *skb = qdisc_dequeue_internal(sch, true); + + q->memory_used -= skb->truesize; + qdisc_qstats_backlog_dec(sch, skb); + rtnl_qdisc_drop(skb, sch); + } + qdisc_tree_reduce_backlog(sch, old_qlen - qdisc_qlen(sch), + old_backlog - sch->qstats.backlog); + + sch_tree_unlock(sch); + return 0; +} + +/* Default alpha/beta values give a 10dB stability margin with max_rtt=100ms. */ +static void dualpi2_reset_default(struct Qdisc *sch) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + + q->sch->limit = 10000; /* Max 125ms at 1Gbps */ + q->memory_limit = get_memory_limit(sch, q->sch->limit); + + q->pi2_target = 15 * NSEC_PER_MSEC; + q->pi2_tupdate = 16 * NSEC_PER_MSEC; + q->pi2_alpha = dualpi2_scale_alpha_beta(41); /* ~0.16 Hz * 256 */ + q->pi2_beta = dualpi2_scale_alpha_beta(819); /* ~3.20 Hz * 256 */ + + q->step_thresh = 1 * NSEC_PER_MSEC; + q->step_in_packets = false; + + dualpi2_calculate_c_protection(q->sch, q, 10); /* wc=10%, wl=90% */ + + q->ecn_mask = TC_DUALPI2_ECN_MASK_L4S_ECT; /* INET_ECN_ECT_1 */ + q->min_qlen_step = 0; /* Always apply step mark in L-queue */ + q->coupling_factor = 2; /* window fairness for equal RTTs */ + q->drop_overload = TC_DUALPI2_DROP_OVERLOAD_DROP; /* Drop overload */ + q->drop_early = TC_DUALPI2_DROP_EARLY_DROP_DEQUEUE; /* Drop dequeue */ + q->split_gso = TC_DUALPI2_SPLIT_GSO_SPLIT_GSO; /* Split GSO */ +} + +static int dualpi2_init(struct Qdisc *sch, struct nlattr *opt, + struct netlink_ext_ack *extack) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + int err; + + q->l_queue = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, + TC_H_MAKE(sch->handle, 1), extack); + if (!q->l_queue) + return -ENOMEM; + + err = tcf_block_get(&q->tcf_block, &q->tcf_filters, sch, extack); + if (err) + return err; + + q->sch = sch; + dualpi2_reset_default(sch); + hrtimer_setup(&q->pi2_timer, dualpi2_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); + + if (opt && nla_len(opt)) { + err = dualpi2_change(sch, opt, extack); + + if (err) + return err; + } + + hrtimer_start(&q->pi2_timer, next_pi2_timeout(q), + HRTIMER_MODE_ABS_PINNED); + return 0; +} + +static int dualpi2_dump(struct Qdisc *sch, struct sk_buff *skb) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + struct nlattr *opts; + bool step_in_pkts; + u32 step_th; + + step_in_pkts = READ_ONCE(q->step_in_packets); + step_th = READ_ONCE(q->step_thresh); + + opts = nla_nest_start_noflag(skb, TCA_OPTIONS); + if (!opts) + goto nla_put_failure; + + if (step_in_pkts && + (nla_put_u32(skb, TCA_DUALPI2_LIMIT, READ_ONCE(sch->limit)) || + nla_put_u32(skb, TCA_DUALPI2_MEMORY_LIMIT, + READ_ONCE(q->memory_limit)) || + nla_put_u32(skb, TCA_DUALPI2_TARGET, + convert_ns_to_usec(READ_ONCE(q->pi2_target))) || + nla_put_u32(skb, TCA_DUALPI2_TUPDATE, + convert_ns_to_usec(READ_ONCE(q->pi2_tupdate))) || + nla_put_u32(skb, TCA_DUALPI2_ALPHA, + dualpi2_unscale_alpha_beta(READ_ONCE(q->pi2_alpha))) || + nla_put_u32(skb, TCA_DUALPI2_BETA, + dualpi2_unscale_alpha_beta(READ_ONCE(q->pi2_beta))) || + nla_put_u32(skb, TCA_DUALPI2_STEP_THRESH_PKTS, step_th) || + nla_put_u32(skb, TCA_DUALPI2_MIN_QLEN_STEP, + READ_ONCE(q->min_qlen_step)) || + nla_put_u8(skb, TCA_DUALPI2_COUPLING, + READ_ONCE(q->coupling_factor)) || + nla_put_u8(skb, TCA_DUALPI2_DROP_OVERLOAD, + READ_ONCE(q->drop_overload)) || + nla_put_u8(skb, TCA_DUALPI2_DROP_EARLY, + READ_ONCE(q->drop_early)) || + nla_put_u8(skb, TCA_DUALPI2_C_PROTECTION, + READ_ONCE(q->c_protection_wc)) || + nla_put_u8(skb, TCA_DUALPI2_ECN_MASK, READ_ONCE(q->ecn_mask)) || + nla_put_u8(skb, TCA_DUALPI2_SPLIT_GSO, READ_ONCE(q->split_gso)))) + goto nla_put_failure; + + if (!step_in_pkts && + (nla_put_u32(skb, TCA_DUALPI2_LIMIT, READ_ONCE(sch->limit)) || + nla_put_u32(skb, TCA_DUALPI2_MEMORY_LIMIT, + READ_ONCE(q->memory_limit)) || + nla_put_u32(skb, TCA_DUALPI2_TARGET, + convert_ns_to_usec(READ_ONCE(q->pi2_target))) || + nla_put_u32(skb, TCA_DUALPI2_TUPDATE, + convert_ns_to_usec(READ_ONCE(q->pi2_tupdate))) || + nla_put_u32(skb, TCA_DUALPI2_ALPHA, + dualpi2_unscale_alpha_beta(READ_ONCE(q->pi2_alpha))) || + nla_put_u32(skb, TCA_DUALPI2_BETA, + dualpi2_unscale_alpha_beta(READ_ONCE(q->pi2_beta))) || + nla_put_u32(skb, TCA_DUALPI2_STEP_THRESH_US, + convert_ns_to_usec(step_th)) || + nla_put_u32(skb, TCA_DUALPI2_MIN_QLEN_STEP, + READ_ONCE(q->min_qlen_step)) || + nla_put_u8(skb, TCA_DUALPI2_COUPLING, + READ_ONCE(q->coupling_factor)) || + nla_put_u8(skb, TCA_DUALPI2_DROP_OVERLOAD, + READ_ONCE(q->drop_overload)) || + nla_put_u8(skb, TCA_DUALPI2_DROP_EARLY, + READ_ONCE(q->drop_early)) || + nla_put_u8(skb, TCA_DUALPI2_C_PROTECTION, + READ_ONCE(q->c_protection_wc)) || + nla_put_u8(skb, TCA_DUALPI2_ECN_MASK, READ_ONCE(q->ecn_mask)) || + nla_put_u8(skb, TCA_DUALPI2_SPLIT_GSO, READ_ONCE(q->split_gso)))) + goto nla_put_failure; + + return nla_nest_end(skb, opts); + +nla_put_failure: + nla_nest_cancel(skb, opts); + return -1; +} + +static int dualpi2_dump_stats(struct Qdisc *sch, struct gnet_dump *d) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + struct tc_dualpi2_xstats st = { + .prob = READ_ONCE(q->pi2_prob), + .packets_in_c = q->packets_in_c, + .packets_in_l = q->packets_in_l, + .maxq = q->maxq, + .ecn_mark = q->ecn_mark, + .credit = q->c_protection_credit, + .step_marks = q->step_marks, + .memory_used = q->memory_used, + .max_memory_used = q->max_memory_used, + .memory_limit = q->memory_limit, + }; + u64 qc, ql; + + get_queue_delays(q, &qc, &ql); + st.delay_l = convert_ns_to_usec(ql); + st.delay_c = convert_ns_to_usec(qc); + return gnet_stats_copy_app(d, &st, sizeof(st)); +} + +/* Reset both L-queue and C-queue, internal packet counters, PI probability, + * C-queue protection credit, and timestamps, while preserving current + * configuration of DUALPI2. + */ +static void dualpi2_reset(struct Qdisc *sch) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + + qdisc_reset_queue(sch); + qdisc_reset_queue(q->l_queue); + q->c_head_ts = 0; + q->l_head_ts = 0; + q->pi2_prob = 0; + q->packets_in_c = 0; + q->packets_in_l = 0; + q->maxq = 0; + q->ecn_mark = 0; + q->step_marks = 0; + q->memory_used = 0; + q->max_memory_used = 0; + dualpi2_reset_c_protection(q); +} + +static void dualpi2_destroy(struct Qdisc *sch) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + + q->pi2_tupdate = 0; + hrtimer_cancel(&q->pi2_timer); + if (q->l_queue) + qdisc_put(q->l_queue); + tcf_block_put(q->tcf_block); +} + +static struct Qdisc *dualpi2_leaf(struct Qdisc *sch, unsigned long arg) +{ + return NULL; +} + +static unsigned long dualpi2_find(struct Qdisc *sch, u32 classid) +{ + return 0; +} + +static unsigned long dualpi2_bind(struct Qdisc *sch, unsigned long parent, + u32 classid) +{ + return 0; +} + +static void dualpi2_unbind(struct Qdisc *q, unsigned long cl) +{ +} + +static struct tcf_block *dualpi2_tcf_block(struct Qdisc *sch, unsigned long cl, + struct netlink_ext_ack *extack) +{ + struct dualpi2_sched_data *q = qdisc_priv(sch); + + if (cl) + return NULL; + return q->tcf_block; +} + +static void dualpi2_walk(struct Qdisc *sch, struct qdisc_walker *arg) +{ + unsigned int i; + + if (arg->stop) + return; + + /* We statically define only 2 queues */ + for (i = 0; i < 2; i++) { + if (arg->count < arg->skip) { + arg->count++; + continue; + } + if (arg->fn(sch, i + 1, arg) < 0) { + arg->stop = 1; + break; + } + arg->count++; + } +} + +/* Minimal class support to handle tc filters */ +static const struct Qdisc_class_ops dualpi2_class_ops = { + .leaf = dualpi2_leaf, + .find = dualpi2_find, + .tcf_block = dualpi2_tcf_block, + .bind_tcf = dualpi2_bind, + .unbind_tcf = dualpi2_unbind, + .walk = dualpi2_walk, +}; + +static struct Qdisc_ops dualpi2_qdisc_ops __read_mostly = { + .id = "dualpi2", + .cl_ops = &dualpi2_class_ops, + .priv_size = sizeof(struct dualpi2_sched_data), + .enqueue = dualpi2_qdisc_enqueue, + .dequeue = dualpi2_qdisc_dequeue, + .peek = qdisc_peek_dequeued, + .init = dualpi2_init, + .destroy = dualpi2_destroy, + .reset = dualpi2_reset, + .change = dualpi2_change, + .dump = dualpi2_dump, + .dump_stats = dualpi2_dump_stats, + .owner = THIS_MODULE, +}; + +static int __init dualpi2_module_init(void) +{ + return register_qdisc(&dualpi2_qdisc_ops); +} + +static void __exit dualpi2_module_exit(void) +{ + unregister_qdisc(&dualpi2_qdisc_ops); +} + +module_init(dualpi2_module_init); +module_exit(dualpi2_module_exit); + +MODULE_DESCRIPTION("Dual Queue with Proportional Integral controller Improved with a Square (dualpi2) scheduler"); +MODULE_AUTHOR("Koen De Schepper <koen.de_schepper@nokia-bell-labs.com>"); +MODULE_AUTHOR("Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>"); +MODULE_AUTHOR("Olga Albisser <olga@albisser.org>"); +MODULE_AUTHOR("Henrik Steen <henrist@henrist.net>"); +MODULE_AUTHOR("Olivier Tilmans <olivier.tilmans@nokia.com>"); + +MODULE_LICENSE("Dual BSD/GPL"); +MODULE_VERSION("1.0"); |