[PATCH net-next v2 1/2] net/sched: sch_fq_pie: add per-flow statistics via class ops
flat view
STALE130d
SUPERSEDED
From: Hemendra M. Naik <hidden>
Date: 2026-06-14 12:50:51
Also in:
linux-kselftest, lkml
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
Revision v2 of 9 in this series.
Revisions (9)
FQ-PIE schedules independent PIE controllers per flow but exposes no
per-flow AQM state. Without class-level statistics there is no way to
observe the per-flow drop probability, queue delay, deficit or
dequeue rate from userspace.
Extend tc_fq_pie_xstats to support both qdisc and class-level
extended statistics.
- Add enum with QDISC and CLASS type discriminators.
- Add struct tc_fq_pie_cl_stats for per-flow metrics (prob,
delay, deficit, avg_dq_rate, dq_rate_estimating).
- Add empty struct tc_fq_pie_xqd_stats placeholder.
Wire up fq_pie_class_ops (.walk, .dump, .dump_stats) so that
'tc -s class show' against an fq_pie qdisc reports per-flow state:
prob per-flow PIE drop probability
delay per-flow queue sojourn time (microseconds)
deficit remaining DRR byte credits (signed integer)
avg_dq_rate dequeue rate estimate in bytes/second
(dq_rate_estimator mode only)
dq_rate_estimating flag indicating active delay estimation mode
Fix the 'delay' field comment in struct tc_pie_xstats from "in ms" to
"in microseconds" to match the kernel's
PSCHED_TICKS2NS / NSEC_PER_USEC conversion.
Also correct the avg_dq_rate comment in tc_pie_xstats from
"bits/pie_time" to "bytes/second" to match the actual kernel
conversion (avg_dq_rate * PSCHED_TICKS_PER_SEC >> PIE_SCALE).
Signed-off-by: Hemendra M. Naik <redacted>
Signed-off-by: Vishal Kamath <redacted>
Signed-off-by: Mohit P. Tahiliani <redacted>
---
Changelog:
v2: Addressed ABI backward compatibility issue for tc_fq_pie_xstats.
v1: https://lore.kernel.org/netdev/20260531125314.22492-2-hemendranaik@gmail.com (local)
---
include/uapi/linux/pkt_sched.h | 29 ++++++-
net/sched/sch_fq_pie.c | 118 +++++++++++++++++++++++++--
tools/include/uapi/linux/pkt_sched.h | 4 +-
3 files changed, 141 insertions(+), 10 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 66e8072f44df..fd4daad98abc 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h@@ -910,9 +910,9 @@ enum { struct tc_pie_xstats { __u64 prob; /* current probability */ - __u32 delay; /* current delay in ms */ + __u32 delay; /* current delay in microseconds */ __u32 avg_dq_rate; /* current average dq_rate in - * bits/pie_time + * bytes/second */ __u32 dq_rate_estimating; /* is avg_dq_rate being calculated? */ __u32 packets_in; /* total number of packets enqueued */
@@ -943,6 +943,25 @@ enum { }; #define TCA_FQ_PIE_MAX (__TCA_FQ_PIE_MAX - 1) +enum { + TCA_FQ_PIE_XSTATS_QDISC, + TCA_FQ_PIE_XSTATS_CLASS, +}; + +struct tc_fq_pie_cl_stats { + __u64 prob; /* current probability */ + __u32 delay; /* current delay in microseconds */ + __s32 deficit; /* number of remaining byte credits */ + __u32 avg_dq_rate; /* current average dq_rate in + * bytes/second + */ + __u32 dq_rate_estimating; /* is avg_dq_rate being calculated? */ +}; + +struct tc_fq_pie_xqd_stats { + /* placeholder for new qdisc-level stats */ +}; + struct tc_fq_pie_xstats { __u32 packets_in; /* total number of packets enqueued */ __u32 dropped; /* packets dropped due to fq_pie_action */
@@ -953,6 +972,12 @@ struct tc_fq_pie_xstats { __u32 new_flows_len; /* count of flows in new list */ __u32 old_flows_len; /* count of flows in old list */ __u32 memory_usage; /* total memory across all queues */ + __u32 type; + union { + struct tc_fq_pie_cl_stats class_stats; + struct tc_fq_pie_xqd_stats xqdisc_stats; + }; + }; /* CBS */
diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c
index 7becbf5362b3..2778d3cda956 100644
--- a/net/sched/sch_fq_pie.c
+++ b/net/sched/sch_fq_pie.c@@ -330,7 +330,7 @@ static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt, /* tupdate is in jiffies */ if (tb[TCA_FQ_PIE_TUPDATE]) WRITE_ONCE(q->p_params.tupdate, - usecs_to_jiffies(nla_get_u32(tb[TCA_FQ_PIE_TUPDATE]))); + usecs_to_jiffies(nla_get_u32(tb[TCA_FQ_PIE_TUPDATE]))); if (tb[TCA_FQ_PIE_ALPHA]) WRITE_ONCE(q->p_params.alpha,
@@ -509,7 +509,9 @@ static int fq_pie_dump(struct Qdisc *sch, struct sk_buff *skb) static int fq_pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d) { struct fq_pie_sched_data *q = qdisc_priv(sch); - struct tc_fq_pie_xstats st = { 0 }; + struct tc_fq_pie_xstats st = { + .type = TCA_FQ_PIE_XSTATS_QDISC, + }; struct list_head *pos; sch_tree_lock(sch);
@@ -517,10 +519,10 @@ static int fq_pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d) st.packets_in = q->stats.packets_in; st.overlimit = q->stats.overlimit; st.overmemory = q->overmemory; - st.dropped = q->stats.dropped; - st.ecn_mark = q->stats.ecn_mark; - st.new_flow_count = q->new_flow_count; - st.memory_usage = q->memory_usage; + st.dropped = q->stats.dropped; + st.ecn_mark = q->stats.ecn_mark; + st.new_flow_count = q->new_flow_count; + st.memory_usage = q->memory_usage; list_for_each(pos, &q->new_flows) st.new_flows_len++;
@@ -561,7 +563,111 @@ static void fq_pie_destroy(struct Qdisc *sch) kvfree(q->flows); } +static struct Qdisc *fq_pie_leaf(struct Qdisc *sch, unsigned long arg) +{ + return NULL; +} + +static unsigned long fq_pie_find(struct Qdisc *sch, u32 classid) +{ + return 0; +} + +static unsigned long fq_pie_bind(struct Qdisc *sch, unsigned long parent, + u32 classid) +{ + return 0; +} + +static void fq_pie_unbind(struct Qdisc *q, unsigned long cl) +{ +} + +static struct tcf_block *fq_pie_tcf_block(struct Qdisc *sch, unsigned long cl, + struct netlink_ext_ack *extack) +{ + struct fq_pie_sched_data *q = qdisc_priv(sch); + + if (cl) + return NULL; + return q->block; +} + +static int fq_pie_dump_class(struct Qdisc *sch, unsigned long cl, + struct sk_buff *skb, struct tcmsg *tcm) +{ + tcm->tcm_handle |= TC_H_MIN(cl); + return 0; +} + +static int fq_pie_dump_class_stats(struct Qdisc *sch, unsigned long cl, + struct gnet_dump *d) +{ + struct fq_pie_sched_data *q = qdisc_priv(sch); + struct gnet_stats_queue qs = { 0 }; + struct tc_fq_pie_xstats xstats; + u32 idx = cl - 1; + + if (idx < q->flows_cnt) { + const struct fq_pie_flow *flow = &q->flows[idx]; + + memset(&xstats, 0, sizeof(xstats)); + xstats.type = TCA_FQ_PIE_XSTATS_CLASS; + xstats.class_stats.prob = READ_ONCE(flow->vars.prob) << BITS_PER_BYTE; + xstats.class_stats.delay = + ((u32)PSCHED_TICKS2NS(READ_ONCE(flow->vars.qdelay))) / + NSEC_PER_USEC; + xstats.class_stats.deficit = READ_ONCE(flow->deficit); + xstats.class_stats.dq_rate_estimating = + READ_ONCE(q->p_params.dq_rate_estimator); + + if (xstats.class_stats.dq_rate_estimating) { + xstats.class_stats.avg_dq_rate = + READ_ONCE(flow->vars.avg_dq_rate) * + (PSCHED_TICKS_PER_SEC) >> PIE_SCALE; + } + + qs.qlen = READ_ONCE(flow->qlen); + qs.backlog = READ_ONCE(flow->backlog); + } + if (gnet_stats_copy_queue(d, NULL, &qs, qs.qlen) < 0) + return -1; + if (idx < q->flows_cnt) + return gnet_stats_copy_app(d, &xstats, sizeof(xstats)); + return 0; +} + +static void fq_pie_walk(struct Qdisc *sch, struct qdisc_walker *arg) +{ + struct fq_pie_sched_data *q = qdisc_priv(sch); + unsigned int i; + + if (arg->stop) + return; + + for (i = 0; i < q->flows_cnt; i++) { + if (list_empty(&q->flows[i].flowchain)) { + arg->count++; + continue; + } + if (!tc_qdisc_stats_dump(sch, i + 1, arg)) + break; + } +} + +static const struct Qdisc_class_ops fq_pie_class_ops = { + .leaf = fq_pie_leaf, + .find = fq_pie_find, + .tcf_block = fq_pie_tcf_block, + .bind_tcf = fq_pie_bind, + .unbind_tcf = fq_pie_unbind, + .dump = fq_pie_dump_class, + .dump_stats = fq_pie_dump_class_stats, + .walk = fq_pie_walk, +}; + static struct Qdisc_ops fq_pie_qdisc_ops __read_mostly = { + .cl_ops = &fq_pie_class_ops, .id = "fq_pie", .priv_size = sizeof(struct fq_pie_sched_data), .enqueue = fq_pie_qdisc_enqueue,
diff --git a/tools/include/uapi/linux/pkt_sched.h b/tools/include/uapi/linux/pkt_sched.h
index 587481a19433..45ea10026742 100644
--- a/tools/include/uapi/linux/pkt_sched.h
+++ b/tools/include/uapi/linux/pkt_sched.h@@ -847,8 +847,8 @@ enum { struct tc_pie_xstats { __u32 prob; /* current probability */ - __u32 delay; /* current delay in ms */ - __u32 avg_dq_rate; /* current average dq_rate in bits/pie_time */ + __u32 delay; /* current delay in micoseconds */ + __u32 avg_dq_rate; /* current average dq_rate in bytes/second */ __u32 packets_in; /* total number of packets enqueued */ __u32 dropped; /* packets dropped due to pie_action */ __u32 overlimit; /* dropped due to lack of space in queue */
--
2.34.1