[PATCH iproute2-next v4 1/3] tc: fq_pie: add support for printing per-flow PIE statistics
From: Hemendra M. Naik
Date: Mon Jul 27 2026 - 13:10:36 EST
`tc -s class show` for an fq_pie qdisc now prints the following
per-flow PIE statistics:
prob drop probability for the flow
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)
avg_dq_rate is formatted using tc_print_rate(), which converts the
kernel's bytes/second value to a human-readable bits/second string
(e.g. 3906Kbit), consistent with how other tc schedulers display
rate fields.
Update the UAPI header to mirror tc_fq_pie_cl_stats from the kernel.
Add `tc -s class show` examples to tc-fq_pie(8) demonstrating the new
per-flow statistics with and without dq_rate_estimator enabled.
Signed-off-by: Hemendra M. Naik <hemendranaik@xxxxxxxxx>
Signed-off-by: Vishal Kamath <vishy0777@xxxxxxxxx>
Signed-off-by: Mohit P. Tahiliani <tahiliani@xxxxxxxxxxx>
---
include/uapi/linux/pkt_sched.h | 25 ++++++++++++++
man/man8/tc-fq_pie.8 | 18 +++++++++++
tc/q_fq_pie.c | 59 +++++++++++++++++++++++-----------
3 files changed, 83 insertions(+), 19 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index d1f67ef8..b99312d2 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/man/man8/tc-fq_pie.8 b/man/man8/tc-fq_pie.8
index 457a56bb..8027783c 100644
--- a/man/man8/tc-fq_pie.8
+++ b/man/man8/tc-fq_pie.8
@@ -153,6 +153,24 @@ dq_rate_estimator
pkts_in 6082 overlimit 0 overmemory 0 dropped 4 ecn_mark 0
new_flow_count 94 new_flows_len 0 old_flows_len 8 memory_used 1157632
+# tc qdisc add dev eth0 parent 100:1 handle 200: fq_pie target 2ms flows 3
+.br
+# tc -s class show dev eth0
+.br
+class fq_pie 200:2 parent 200:
+ Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
+ backlog 22800b 2p requeues 0
+ prob 0.57679 delay 2.38ms deficit -52
+
+# tc qdisc add dev eth0 parent 100:1 handle 200: fq_pie target 2ms flows 3 dq_rate_estimator
+.br
+# tc -s class show dev eth0
+.br
+class fq_pie 200:2 parent 200:
+ Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
+ backlog 22800b 2p requeues 0
+ prob 0.57679 delay 2.38ms deficit -52 avg_dq_rate 10742Kbit
+
.SH SEE ALSO
.BR tc (8),
.BR tc-pie (8),
diff --git a/tc/q_fq_pie.c b/tc/q_fq_pie.c
index dc2710cd..1b89ee3a 100644
--- a/tc/q_fq_pie.c
+++ b/tc/q_fq_pie.c
@@ -274,6 +274,8 @@ static int fq_pie_print_xstats(const struct qdisc_util *qu, FILE *f,
{
struct tc_fq_pie_xstats _st = {}, *st;
+ SPRINT_BUF(b1);
+
if (xstats == NULL)
return 0;
@@ -283,25 +285,44 @@ static int fq_pie_print_xstats(const struct qdisc_util *qu, FILE *f,
st = &_st;
}
- print_uint(PRINT_ANY, "pkts_in", " pkts_in %u",
- st->packets_in);
- print_uint(PRINT_ANY, "overlimit", " overlimit %u",
- st->overlimit);
- print_uint(PRINT_ANY, "overmemory", " overmemory %u",
- st->overmemory);
- print_uint(PRINT_ANY, "dropped", " dropped %u",
- st->dropped);
- print_uint(PRINT_ANY, "ecn_mark", " ecn_mark %u",
- st->ecn_mark);
- print_nl();
- print_uint(PRINT_ANY, "new_flow_count", " new_flow_count %u",
- st->new_flow_count);
- print_uint(PRINT_ANY, "new_flows_len", " new_flows_len %u",
- st->new_flows_len);
- print_uint(PRINT_ANY, "old_flows_len", " old_flows_len %u",
- st->old_flows_len);
- print_uint(PRINT_ANY, "memory_used", " memory_used %u",
- st->memory_usage);
+ if (!st->type || st->type == TCA_FQ_PIE_XSTATS_QDISC) {
+ print_uint(PRINT_ANY, "pkts_in", " pkts_in %u",
+ st->packets_in);
+ print_uint(PRINT_ANY, "overlimit", " overlimit %u",
+ st->overlimit);
+ print_uint(PRINT_ANY, "overmemory", " overmemory %u",
+ st->overmemory);
+ print_uint(PRINT_ANY, "dropped", " dropped %u",
+ st->dropped);
+ print_uint(PRINT_ANY, "ecn_mark", " ecn_mark %u",
+ st->ecn_mark);
+ print_nl();
+ print_uint(PRINT_ANY, "new_flow_count", " new_flow_count %u",
+ st->new_flow_count);
+ print_uint(PRINT_ANY, "new_flows_len", " new_flows_len %u",
+ st->new_flows_len);
+ print_uint(PRINT_ANY, "old_flows_len", " old_flows_len %u",
+ st->old_flows_len);
+ print_uint(PRINT_ANY, "memory_used", " memory_used %u",
+ st->memory_usage);
+ print_nl();
+ }
+
+ if (st->type == TCA_FQ_PIE_XSTATS_CLASS) {
+ print_float(PRINT_ANY, "prob", " prob %lg",
+ (double)st->class_stats.prob / (double)UINT64_MAX);
+ print_uint(PRINT_JSON, "delay", NULL, st->class_stats.delay);
+ print_string(PRINT_FP, NULL, " delay %s",
+ sprint_time(st->class_stats.delay, b1));
+ print_int(PRINT_ANY, "deficit", " deficit %d",
+ st->class_stats.deficit);
+
+ if (st->class_stats.dq_rate_estimating) {
+ tc_print_rate(PRINT_ANY, "avg_dq_rate", " avg_dq_rate %s",
+ st->class_stats.avg_dq_rate);
+ }
+ print_nl();
+ }
return 0;
--
2.34.1