[PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[Manjusaka]

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@manjusaka.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);
 	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

Re: [PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[Eric Dumazet]

On Sun, Aug 6, 2023 at 9:52 AM Manjusaka <me@manjusaka.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@manjusaka.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 ?

Re: [PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[Manjusaka]

> 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@manjusaka.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@manjusaka.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 ?
> 

Re: [PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[Eric Dumazet]

On Mon, Aug 7, 2023 at 2:49 PM Manjusaka <me@manjusaka.me> wrote:
>
> > 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?

I am speaking of tcp_ca_event()...

For instance, tcp_cwnd_restart() calls tcp_ca_event(sk, CA_EVENT_CWND_RESTART);

tcp_set_ca_state() can only set icsk_ca_state to one value from enum
tcp_ca_state:
TCP_CA_Open, TCP_CA_Disorder, TCP_CA_CWR, TCP_CA_Recovery, TCP_CA_Loss

enum tcp_ca_event has instead:
CA_EVENT_TX_START, CA_EVENT_CWND_RESTART, CA_EVENT_COMPLETE_CWR,
CA_EVENT_LOSS, CA_EVENT_ECN_NO_CE, CA_EVENT_ECN_IS_CE

Re: [PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[Manjusaka]

Got you means! LGTM

I will make a patch later and make a try

On Mon, Aug 7, 2023, at 9:25 PM, Eric Dumazet wrote:
> On Mon, Aug 7, 2023 at 2:49 PM Manjusaka <me@manjusaka.me> wrote:
> >
> > > 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?
> 
> I am speaking of tcp_ca_event()...
> 
> For instance, tcp_cwnd_restart() calls tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
> 
> tcp_set_ca_state() can only set icsk_ca_state to one value from enum
> tcp_ca_state:
> TCP_CA_Open, TCP_CA_Disorder, TCP_CA_CWR, TCP_CA_Recovery, TCP_CA_Loss
> 
> enum tcp_ca_event has instead:
> CA_EVENT_TX_START, CA_EVENT_CWND_RESTART, CA_EVENT_COMPLETE_CWR,
> CA_EVENT_LOSS, CA_EVENT_ECN_NO_CE, CA_EVENT_ECN_IS_CE
>