linux-kernel - Re: [PATCH RFC net-next] trace: tcp: Add tracepoint for tcp_cwnd

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Message-ID: <20250120-panda-of-impressive-aptitude-2b714e@leitao>
Date: Mon, 20 Jan 2025 05:02:37 -0800
From: Breno Leitao <leitao@...ian.org>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, kernel-team@...a.com,
	Yonghong Song <yonghong.song@...ux.dev>, Song Liu <song@...nel.org>,
	Martin KaFai Lau <martin.lau@...nel.org>
Subject: Re: [PATCH RFC net-next] trace: tcp: Add tracepoint for
 tcp_cwnd_reduction()

Hello Jason,

On Mon, Jan 20, 2025 at 08:08:52PM +0800, Jason Xing wrote:
> On Mon, Jan 20, 2025 at 8:03 PM Breno Leitao <leitao@...ian.org> wrote:
> > 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?

Thank you,
--breno