Re: [PATCH net-next] trace: tcp: Add tracepoint for tcp_cwnd_reduction()

From: Steven Rostedt
Date: Tue Feb 11 2025 - 12:05:39 EST


On Tue, 11 Feb 2025 16:19:54 +0100
Eric Dumazet <edumazet@xxxxxxxxxx> wrote:

> I can give my +2 on this patch, although I have no way of testing it.

If you want to test this, apply the below patch, enable
CONFIG_SAMPLE_TRACE_CUSTOM_EVENTS, and after you boot up, do the following:

# modprobe trace_custom_sched
# cd /sys/kernel/tracing
# echo 1 > events/custom/tcp_cwnd_reduction_tp/enable

[ do something to trigger it ]

# cat trace

-- Steve

diff --git a/samples/trace_events/trace_custom_sched.c b/samples/trace_events/trace_custom_sched.c
index dd409b704b35..35b3cfa6e91d 100644
--- a/samples/trace_events/trace_custom_sched.c
+++ b/samples/trace_events/trace_custom_sched.c
@@ -16,6 +16,7 @@
* from the C file, and not in the custom header file.
*/
#include <trace/events/sched.h>
+#include <trace/events/tcp.h>

/* Declare CREATE_CUSTOM_TRACE_EVENTS before including custom header */
#define CREATE_CUSTOM_TRACE_EVENTS
@@ -37,6 +38,7 @@
*/
static void fct(struct tracepoint *tp, void *priv)
{
+ trace_custom_event_tcp_cwnd_reduction_tp_update(tp);
trace_custom_event_sched_switch_update(tp);
trace_custom_event_sched_waking_update(tp);
}
diff --git a/samples/trace_events/trace_custom_sched.h b/samples/trace_events/trace_custom_sched.h
index 951388334a3f..339957d692c0 100644
--- a/samples/trace_events/trace_custom_sched.h
+++ b/samples/trace_events/trace_custom_sched.h
@@ -74,6 +74,33 @@ TRACE_CUSTOM_EVENT(sched_waking,

TP_printk("pid=%d prio=%d", __entry->pid, __entry->prio)
)
+
+struct sock;
+
+TRACE_CUSTOM_EVENT(tcp_cwnd_reduction_tp,
+
+ TP_PROTO(const struct sock *sk, int newly_acked_sacked,
+ int newly_lost, int flag),
+
+ TP_ARGS(sk, newly_acked_sacked, newly_lost, flag),
+
+ TP_STRUCT__entry(
+ __field( unsigned long, sk )
+ __field( int, ack )
+ __field( int, lost )
+ __field( int, flag )
+ ),
+
+ TP_fast_assign(
+ __entry->sk = (unsigned long)sk;
+ __entry->ack = newly_acked_sacked;
+ __entry->lost = newly_lost;
+ __entry->flag = flag;
+ ),
+
+ TP_printk("sk=%lx ack=%d lost=%d flag=%d", __entry->sk,
+ __entry->ack, __entry->lost, __entry->flag)
+)
#endif
/*
* Just like the headers that create TRACE_EVENTs, the below must