From e72aeb9ee0e34c57dc90793d0bf82cab9624d64e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 14 Oct 2021 10:59:18 -0700 Subject: [PATCH] fq_codel: implement L4S style ce_threshold_ect1 marking Add TCA_FQ_CODEL_CE_THRESHOLD_ECT1 boolean option to select Low Latency, Low Loss, Scalable Throughput (L4S) style marking, along with ce_threshold. If enabled, only packets with ECT(1) can be transformed to CE if their sojourn time is above the ce_threshold. Note that this new option does not change rules for codel law. In particular, if TCA_FQ_CODEL_ECN is left enabled (this is the default when fq_codel qdisc is created), ECT(0) packets can still get CE if codel law (as governed by limit/target) decides so. Section 4.3.b of current draft [1] states: b. A scheduler with per-flow queues such as FQ-CoDel or FQ-PIE can be used for L4S. For instance within each queue of an FQ-CoDel system, as well as a CoDel AQM, there is typically also ECN marking at an immediate (unsmoothed) shallow threshold to support use in data centres (see Sec.5.2.7 of [RFC8290]). This can be modified so that the shallow threshold is solely applied to ECT(1) packets. Then if there is a flow of non-ECN or ECT(0) packets in the per-flow-queue, the Classic AQM (e.g. CoDel) is applied; while if there is a flow of ECT(1) packets in the queue, the shallower (typically sub-millisecond) threshold is applied. Tested: tc qd replace dev eth1 root fq_codel ce_threshold_ect1 50usec netperf ... -t TCP_STREAM -- K dctcp tc -s -d qd sh dev eth1 qdisc fq_codel 8022: root refcnt 32 limit 10240p flows 1024 quantum 9212 target 5ms ce_threshold_ect1 49us interval 100ms memory_limit 32Mb ecn drop_batch 64 Sent 14388596616 bytes 9543449 pkt (dropped 0, overlimits 0 requeues 152013) backlog 0b 0p requeues 152013 maxpacket 68130 drop_overlimit 0 new_flow_count 95678 ecn_mark 0 ce_mark 7639 new_flows_len 0 old_flows_len 0 [1] L4S current draft: https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-l4s-arch Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Ingemar Johansson S Cc: Tom Henderson Cc: Bob Briscoe Signed-off-by: David S. Miller --- include/net/codel.h | 2 ++ include/net/codel_impl.h | 18 +++++++++++++++--- include/uapi/linux/pkt_sched.h | 1 + net/mac80211/sta_info.c | 1 + net/sched/sch_fq_codel.c | 15 +++++++++++---- 5 files changed, 30 insertions(+), 7 deletions(-) diff --git a/include/net/codel.h b/include/net/codel.h index a6e428f80135..5e8b181b76b8 100644 --- a/include/net/codel.h +++ b/include/net/codel.h @@ -102,6 +102,7 @@ static inline u32 codel_time_to_us(codel_time_t val) * @interval: width of moving time window * @mtu: device mtu, or minimal queue backlog in bytes. * @ecn: is Explicit Congestion Notification enabled + * @ce_threshold_ect1: if ce_threshold only marks ECT(1) packets */ struct codel_params { codel_time_t target; @@ -109,6 +110,7 @@ struct codel_params { codel_time_t interval; u32 mtu; bool ecn; + bool ce_threshold_ect1; }; /** diff --git a/include/net/codel_impl.h b/include/net/codel_impl.h index d289b91dcd65..7af2c3eb3c43 100644 --- a/include/net/codel_impl.h +++ b/include/net/codel_impl.h @@ -54,6 +54,7 @@ static void codel_params_init(struct codel_params *params) params->interval = MS2TIME(100); params->target = MS2TIME(5); params->ce_threshold = CODEL_DISABLED_THRESHOLD; + params->ce_threshold_ect1 = false; params->ecn = false; } @@ -246,9 +247,20 @@ static struct sk_buff *codel_dequeue(void *ctx, vars->rec_inv_sqrt); } end: - if (skb && codel_time_after(vars->ldelay, params->ce_threshold) && - INET_ECN_set_ce(skb)) - stats->ce_mark++; + if (skb && codel_time_after(vars->ldelay, params->ce_threshold)) { + bool set_ce = true; + + if (params->ce_threshold_ect1) { + /* Note: if skb_get_dsfield() returns -1, following + * gives INET_ECN_MASK, which is != INET_ECN_ECT_1. + */ + u8 ecn = skb_get_dsfield(skb) & INET_ECN_MASK; + + set_ce = (ecn == INET_ECN_ECT_1); + } + if (set_ce && INET_ECN_set_ce(skb)) + stats->ce_mark++; + } return skb; } diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index ec88590b3198..6be9a84cccfa 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -840,6 +840,7 @@ enum { TCA_FQ_CODEL_CE_THRESHOLD, TCA_FQ_CODEL_DROP_BATCH_SIZE, TCA_FQ_CODEL_MEMORY_LIMIT, + TCA_FQ_CODEL_CE_THRESHOLD_ECT1, __TCA_FQ_CODEL_MAX }; diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c index 2b5acb37587f..a39830418434 100644 --- a/net/mac80211/sta_info.c +++ b/net/mac80211/sta_info.c @@ -513,6 +513,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata, sta->cparams.target = MS2TIME(20); sta->cparams.interval = MS2TIME(100); sta->cparams.ecn = true; + sta->cparams.ce_threshold_ect1 = false; sta_dbg(sdata, "Allocated STA %pM\n", sta->sta.addr); diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index bb0cd6d3d2c2..033d65d06eb1 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -362,6 +362,7 @@ static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = { [TCA_FQ_CODEL_CE_THRESHOLD] = { .type = NLA_U32 }, [TCA_FQ_CODEL_DROP_BATCH_SIZE] = { .type = NLA_U32 }, [TCA_FQ_CODEL_MEMORY_LIMIT] = { .type = NLA_U32 }, + [TCA_FQ_CODEL_CE_THRESHOLD_ECT1] = { .type = NLA_U8 }, }; static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt, @@ -408,6 +409,9 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt, q->cparams.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT; } + if (tb[TCA_FQ_CODEL_CE_THRESHOLD_ECT1]) + q->cparams.ce_threshold_ect1 = !!nla_get_u8(tb[TCA_FQ_CODEL_CE_THRESHOLD_ECT1]); + if (tb[TCA_FQ_CODEL_INTERVAL]) { u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]); @@ -544,10 +548,13 @@ static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb) q->flows_cnt)) goto nla_put_failure; - if (q->cparams.ce_threshold != CODEL_DISABLED_THRESHOLD && - nla_put_u32(skb, TCA_FQ_CODEL_CE_THRESHOLD, - codel_time_to_us(q->cparams.ce_threshold))) - goto nla_put_failure; + if (q->cparams.ce_threshold != CODEL_DISABLED_THRESHOLD) { + if (nla_put_u32(skb, TCA_FQ_CODEL_CE_THRESHOLD, + codel_time_to_us(q->cparams.ce_threshold))) + goto nla_put_failure; + if (nla_put_u8(skb, TCA_FQ_CODEL_CE_THRESHOLD_ECT1, q->cparams.ce_threshold_ect1)) + goto nla_put_failure; + } return nla_nest_end(skb, opts); -- 2.25.1