On Mon, Jan 20, 2025 at 9:02 PM Breno Leitao [off-list ref] wrote:

Hello Jason,

On Mon, Jan 20, 2025 at 08:08:52PM +0800, Jason Xing wrote:

quoted

On Mon, Jan 20, 2025 at 8:03 PM Breno Leitao [off-list ref] wrote:

quoted

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4811727b8a02258ec6fa1fd129beecf7cbb0f90e..fc88c511e81bc12ec57e8dc3e9185a920d1bd079 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c

@@ -2710,6 +2710,8 @@ void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost,
        if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd))
                return;

+       trace_tcp_cwnd_reduction(sk, newly_acked_sacked, newly_lost, flag);
+

Are there any other reasons why introducing a new tracepoint here?
AFAIK, it can be easily replaced by a bpf related program or script to
monitor in the above position.

In which position exactly?

I meant, in the position where you insert a one-line tracepoint, which
should be easily replaced with a bpf program (kprobe
tcp_cwnd_reduction with two checks like in the earlier if-statement).
It doesn't mean that I object to this new tracepoint, just curious if
you have other motivations.

Thanks,
Jason