* [PATCH net-next v4 1/3] net/sched: sch_fq_pie: add per-flow statistics via class ops
2026-07-27 16:40 [PATCH net-next v4 0/3] net/sched: sch_fq_pie: add per-flow class statistics Hemendra M. Naik
@ 2026-07-27 16:40 ` Hemendra M. Naik
2026-07-27 16:40 ` [PATCH net-next v4 2/3] selftests: tc-testing: add fq_pie per-flow class stats test Hemendra M. Naik
2026-07-27 16:40 ` [PATCH net-next v4 3/3] net/sched: pie: correct tc_pie_xstats field documentation Hemendra M. Naik
2 siblings, 0 replies; 4+ messages in thread
From: Hemendra M. Naik @ 2026-07-27 16:40 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 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 whether avg_dq_rate
is being calculated
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 | 25 ++++++++
net/sched/sch_fq_pie.c | 109 ++++++++++++++++++++++++++++++++-
2 files changed, 133 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 490efd288526..9a86fa4d6846 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -953,6 +953,25 @@ 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 */
@@ -963,6 +982,12 @@ 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 72f48fa4010b..664fef18568b 100644
--- a/net/sched/sch_fq_pie.c
+++ b/net/sched/sch_fq_pie.c
@@ -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);
@@ -561,7 +563,112 @@ 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,
--
2.34.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH net-next v4 2/3] selftests: tc-testing: add fq_pie per-flow class stats test
2026-07-27 16:40 [PATCH net-next v4 0/3] net/sched: sch_fq_pie: add per-flow class statistics Hemendra M. Naik
2026-07-27 16:40 ` [PATCH net-next v4 1/3] net/sched: sch_fq_pie: add per-flow statistics via class ops Hemendra M. Naik
@ 2026-07-27 16:40 ` Hemendra M. Naik
2026-07-27 16:40 ` [PATCH net-next v4 3/3] net/sched: pie: correct tc_pie_xstats field documentation Hemendra M. Naik
2 siblings, 0 replies; 4+ messages in thread
From: Hemendra M. Naik @ 2026-07-27 16:40 UTC (permalink / raw)
To: netdev
Cc: davem, edumazet, kuba, pabeni, horms, jiri, jhs, shuah,
linux-kernel, linux-kselftest, vishy0777, tahiliani,
Hemendra M. Naik
Add a tc-testing entry (id: 83c0) to verify the fq_pie class ops
wired up in the previous patch do not crash and integrate cleanly
with the tc class show path.
The test creates an fq_pie root qdisc on a dummy interface and runs
'tc -s class show'.
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 | 22 +++++++++++++++++++
1 file changed, 22 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..88139f429430 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 +40,27 @@
"matchPattern": "qdisc fq_pie 1: root refcnt [0-9]+ limit 1p",
"matchCount": "1",
"teardown": ["$TC qdisc del dev $DEV1 handle 1: root"]
+ },
+ {
+ "id": "83c0",
+ "name": "FQ-PIE class stats accessible via tc class show",
+ "category": [
+ "qdisc",
+ "fq_pie"
+ ],
+ "plugins": {
+ "requires": "nsPlugin"
+ },
+ "setup": [
+ "$TC qdisc add dev $DUMMY handle 1: root fq_pie"
+ ],
+ "cmdUnderTest": "$TC -s class show dev $DUMMY",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s class show dev $DUMMY",
+ "matchPattern": "class fq_pie",
+ "matchCount": "0",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
}
]
--
2.34.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH net-next v4 3/3] net/sched: pie: correct tc_pie_xstats field documentation
2026-07-27 16:40 [PATCH net-next v4 0/3] net/sched: sch_fq_pie: add per-flow class statistics Hemendra M. Naik
2026-07-27 16:40 ` [PATCH net-next v4 1/3] net/sched: sch_fq_pie: add per-flow statistics via class ops Hemendra M. Naik
2026-07-27 16:40 ` [PATCH net-next v4 2/3] selftests: tc-testing: add fq_pie per-flow class stats test Hemendra M. Naik
@ 2026-07-27 16:40 ` Hemendra M. Naik
2 siblings, 0 replies; 4+ messages in thread
From: Hemendra M. Naik @ 2026-07-27 16:40 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 indicate that the value is reported
in microseconds, matching the `PSCHED_TICKS2NS() / NSEC_PER_USEC`
conversion.
Similarly, update the `avg_dq_rate` field comment to indicate that the
value is reported in bytes/second, matching the conversion performed by
`avg_dq_rate * PSCHED_TICKS_PER_SEC >> PIE_SCALE`.
These are documentation-only changes and do not modify the UAPI layout
or runtime behavior.
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 ++--
tools/include/uapi/linux/pkt_sched.h | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 9a86fa4d6846..26b7e6964adb 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 */
diff --git a/tools/include/uapi/linux/pkt_sched.h b/tools/include/uapi/linux/pkt_sched.h
index 587481a19433..9bc190f0b3cf 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 microseconds */
+ __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
^ permalink raw reply related [flat|nested] 4+ messages in thread