* [PATCH net-next v6 1/3] net/sched: sch_fq_pie: add per-flow statistics via class ops
2026-09-17 20:42 [PATCH net-next v6 0/3] net/sched: sch_fq_pie: add per-flow class statistics Hemendra M. Naik
@ 2026-09-17 20:42 ` Hemendra M. Naik
2026-09-17 20:42 ` [PATCH net-next v6 2/3] selftests: tc-testing: add fq_pie per-flow class stats test Hemendra M. Naik
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Hemendra M. Naik @ 2026-09-17 20:42 UTC (permalink / raw)
To: netdev
Cc: davem, edumazet, kuba, pabeni, horms, jiri, jhs, shuah,
linux-kernel, linux-kselftest, vishy0777, tahiliani,
Hemendra M. Naik
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 with a type discriminator and tc_fq_pie_cl_stats
for per-flow metrics. The nine existing __u32 counters keep their
offsets, type is appended at offset 36 and class_stats follows it,
growing the structure from 36 to 64 bytes.
Wire up fq_pie_class_ops with walk, dump, and dump_stats only so that
'tc -s class show' reports per-flow state (prob, delay, deficit,
avg_dq_rate, dq_rate_estimating). Filter attachment callbacks
(.tcf_block, .bind_tcf, .unbind_tcf) are omitted on purpose.
Derive delay with div_u64() from the full 64-bit nanosecond value rather
than truncating to u32 before dividing, which wrapped for sojourn times
above ~4.295 s, and widen avg_dq_rate to u64 before scaling it by
PSCHED_TICKS_PER_SEC.
Signed-off-by: Hemendra M. Naik <hemendranaik@gmail.com>
Signed-off-by: Vishal Kamath <vishy0777@gmail.com>
Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
---
include/uapi/linux/pkt_sched.h | 16 +++++++
net/sched/sch_fq_pie.c | 86 +++++++++++++++++++++++++++++++++-
2 files changed, 101 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 490efd288526..9c0c9787f0c3 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -953,6 +953,20 @@ 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_xstats {
__u32 packets_in; /* total number of packets enqueued */
__u32 dropped; /* packets dropped due to fq_pie_action */
@@ -963,6 +977,8 @@ 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;
+ struct tc_fq_pie_cl_stats class_stats;
};
/* CBS */
diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c
index 5982847df8f8..675861f578b8 100644
--- a/net/sched/sch_fq_pie.c
+++ b/net/sched/sch_fq_pie.c
@@ -511,7 +511,9 @@ 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);
@@ -563,7 +565,89 @@ 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 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 =
+ div_u64(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 =
+ ((u64)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,
+ .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,
--
2.34.1
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH net-next v6 2/3] selftests: tc-testing: add fq_pie per-flow class stats test
2026-09-17 20:42 [PATCH net-next v6 0/3] net/sched: sch_fq_pie: add per-flow class statistics Hemendra M. Naik
2026-09-17 20:42 ` [PATCH net-next v6 1/3] net/sched: sch_fq_pie: add per-flow statistics via class ops Hemendra M. Naik
@ 2026-09-17 20:42 ` Hemendra M. Naik
2026-09-17 20:42 ` [PATCH net-next v6 3/3] net/sched: pie: correct tc_pie_xstats field documentation Hemendra M. Naik
2026-09-18 22:59 ` [PATCH net-next v6 0/3] net/sched: sch_fq_pie: add per-flow class statistics Jakub Kicinski
3 siblings, 0 replies; 6+ messages in thread
From: Hemendra M. Naik @ 2026-09-17 20:42 UTC (permalink / raw)
To: netdev
Cc: davem, edumazet, kuba, pabeni, horms, jiri, jhs, shuah,
linux-kernel, linux-kselftest, vishy0777, tahiliani,
Hemendra M. Naik
Add tc-testing case 83c0: build a TBF + fq_pie hierarchy on $DUMMY, push
traffic through it with ping, and verify that 'tc -s class show' reports
an fq_pie class.
The per-flow counters themselves (prob, delay, deficit) are printed only
after the companion iproute2 change, "tc: fq_pie: add support for printing
per-flow PIE statistics"
Signed-off-by: Hemendra M. Naik <hemendranaik@gmail.com>
Signed-off-by: Vishal Kamath <vishy0777@gmail.com>
Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
---
.../tc-testing/tc-tests/qdiscs/fq_pie.json | 27 +++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json
index 229fe1bf4a90..15b2667285eb 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json
@@ -40,5 +40,32 @@
"matchPattern": "qdisc fq_pie 1: root refcnt [0-9]+ limit 1p",
"matchCount": "1",
"teardown": ["$TC qdisc del dev $DEV1 handle 1: root"]
+ },
+ {
+ "id": "83c0",
+ "name": "FQ-PIE class stats accessible via tc class show",
+ "category": [
+ "qdisc",
+ "fq_pie"
+ ],
+ "plugins": {
+ "requires": "nsPlugin"
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc add dev $DUMMY parent 1:1 handle 2: fq_pie limit 100 flows 1",
+ "ping -c 50 -i 0.001 -W 0.01 -s 56 10.10.11.11 -I $DUMMY > /dev/null 2>&1 || true"
+ ],
+ "cmdUnderTest": "$TC -s class show dev $DUMMY",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s class show dev $DUMMY",
+ "matchPattern": "class fq_pie 2:[0-9]+ .*prob .*delay .*deficit",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root",
+ "$IP addr del 10.10.11.10/24 dev $DUMMY || true"
+ ]
}
]
--
2.34.1
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH net-next v6 3/3] net/sched: pie: correct tc_pie_xstats field documentation
2026-09-17 20:42 [PATCH net-next v6 0/3] net/sched: sch_fq_pie: add per-flow class statistics Hemendra M. Naik
2026-09-17 20:42 ` [PATCH net-next v6 1/3] net/sched: sch_fq_pie: add per-flow statistics via class ops Hemendra M. Naik
2026-09-17 20:42 ` [PATCH net-next v6 2/3] selftests: tc-testing: add fq_pie per-flow class stats test Hemendra M. Naik
@ 2026-09-17 20:42 ` Hemendra M. Naik
2026-09-18 22:59 ` [PATCH net-next v6 0/3] net/sched: sch_fq_pie: add per-flow class statistics Jakub Kicinski
3 siblings, 0 replies; 6+ messages in thread
From: Hemendra M. Naik @ 2026-09-17 20:42 UTC (permalink / raw)
To: netdev
Cc: davem, edumazet, kuba, pabeni, horms, jiri, jhs, shuah,
linux-kernel, linux-kselftest, vishy0777, tahiliani,
Hemendra M. Naik
The comments describing struct tc_pie_xstats do not match the values
exported by the kernel.
Update the delay field comment to microseconds (PSCHED_TICKS2NS() /
NSEC_PER_USEC). Update avg_dq_rate to bytes/second (avg_dq_rate *
PSCHED_TICKS_PER_SEC >> PIE_SCALE).
Documentation-only; no UAPI layout or runtime change. Touch
include/uapi/linux/pkt_sched.h only
Signed-off-by: Hemendra M. Naik <hemendranaik@gmail.com>
Signed-off-by: Vishal Kamath <vishy0777@gmail.com>
Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
---
include/uapi/linux/pkt_sched.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 9c0c9787f0c3..969fa30efae7 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -920,9 +920,9 @@ 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 */
--
2.34.1
^ permalink raw reply [flat|nested] 6+ messages in thread