[PATCH net-next 2/2] fq_codel: implement L4S style ce_threshold_ect1 marking
From: Eric Dumazet <hidden>
Date: 2021-10-14 17:59:29
Subsystem:
mac80211, networking [general], tc subsystem, the rest · Maintainers:
Johannes Berg, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
From: Eric Dumazet <edumazet@google.com>
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 <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Ingemar Johansson S <redacted>
Cc: Tom Henderson <redacted>
Cc: Bob Briscoe <redacted>
---
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 a6e428f801350809322aaff08d92904e059c3b5a..5e8b181b76b829d6af3c57809d9bc5f0578dd112 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 d289b91dcd65ecdc96dc0c9bf85d4a4be6961022..7af2c3eb3c43c24364519120aad5be77522854a6 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 ec88590b3198441f18cc9def7bd40c48f0bc82a1..6be9a84cccfa79bace1f3f7123d02f484b67a25e 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 2b5acb37587f7068e2d11fe842ec963a556f1eb1..a39830418434d4bb74d238373f63a4858230fce5 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 bb0cd6d3d2c2749d54e26368fb2558beedea85c9..033d65d06eb136ff704cddd3ee950a5c3a5d9831 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);
--
2.33.0.1079.g6e70778dc9-goog