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Date: Thu, 14 Oct 2021 10:59:18 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Neal Cardwell <ncardwell@...gle.com>,
Ingemar Johansson S <ingemar.s.johansson@...csson.com>,
Tom Henderson <tomh@...h.org>, Bob Briscoe <in@...briscoe.net>
Subject: [PATCH net-next 2/2] fq_codel: implement L4S style ce_threshold_ect1 marking
From: Eric Dumazet <edumazet@...gle.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@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>
Cc: Ingemar Johansson S <ingemar.s.johansson@...csson.com>
Cc: Tom Henderson <tomh@...h.org>
Cc: Bob Briscoe <in@...briscoe.net>
---
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
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