linux-kernel - Re: [PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd

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Date:   Mon, 07 Aug 2023 20:51:00 +0800
From:   Manjusaka <me@...jusaka.me>
To:     "Eric Dumazet" <edumazet@...gle.com>
Cc:     mhiramat@...nel.org, rostedt@...dmis.org, davem@...emloft.net,
        dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

> Do not include code before variable declarations.
Sorry about that. I will update the code later.

> I would rather add a trace in tcp_ca_event(), this would be more generic ?

https://elixir.bootlin.com/linux/latest/source/net/ipv4/tcp_cong.c#L41

I think maybe we already have the tcp_ca_event but named tcp_cong_state_set?


On Mon, Aug 7, 2023, at 8:34 PM, Eric Dumazet wrote:
> On Sun, Aug 6, 2023 at 9:52 AM Manjusaka <me@...jusaka.me> wrote:
> >
> > The tcp_cwnd_restart function would be called if the user has enabled the
> > tcp_slow_start_after_idle configuration and would be triggered when the
> > connection is idle (like LONG RTO etc.). I think it would be great to
> > add a new trace event named 'tcp:tcp_cwnd_reset'; it would help people
> > to monitor the TCP state in a complicated network environment(like
> > overlay/underlay SDN in Kubernetes, etc)
> >
> > Signed-off-by: Manjusaka <me@...jusaka.me>
> > ---
> >  include/trace/events/tcp.h | 7 +++++++
> >  net/ipv4/tcp_output.c      | 1 +
> >  2 files changed, 8 insertions(+)
> >
> > diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> > index bf06db8d2046..fa44191cc609 100644
> > --- a/include/trace/events/tcp.h
> > +++ b/include/trace/events/tcp.h
> > @@ -187,6 +187,13 @@ DEFINE_EVENT(tcp_event_sk, tcp_rcv_space_adjust,
> >         TP_ARGS(sk)
> >  );
> >
> > +DEFINE_EVENT(tcp_event_sk, tcp_cwnd_restart,
> > +
> > +       TP_PROTO(struct sock *sk),
> > +
> > +       TP_ARGS(sk)
> > +);
> > +
> >  TRACE_EVENT(tcp_retransmit_synack,
> >
> >         TP_PROTO(const struct sock *sk, const struct request_sock *req),
> > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> > index 51d8638d4b4c..e902fa74303d 100644
> > --- a/net/ipv4/tcp_output.c
> > +++ b/net/ipv4/tcp_output.c
> > @@ -141,6 +141,7 @@ static __u16 tcp_advertise_mss(struct sock *sk)
> >   */
> >  void tcp_cwnd_restart(struct sock *sk, s32 delta)
> >  {
> > +       trace_tcp_cwnd_restart(sk);
> 
> Do not include code before variable declarations.
> 
> >         struct tcp_sock *tp = tcp_sk(sk);
> >         u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
> >         u32 cwnd = tcp_snd_cwnd(tp);
> > --
> > 2.34.1
> >
> 
> I would rather add a trace in tcp_ca_event(), this would be more generic ?
>