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Date:      Mon, 7 Apr 2025 15:35:16 -0400
From:      jaeyong yoo <y.jaeyong@gmail.com>
To:        Cheng Cui <cc@freebsd.org>
Cc:        freebsd-net@freebsd.org, freebsd-transport@freebsd.org
Subject:   Re: HyStart availability in FreeBSD stack
Message-ID:  <CANud0TFNgzwUh9gq7BTGh8m9Jn8=5vkwhigttm1pQefVQOnCeQ@mail.gmail.com>
In-Reply-To: <CANud0TE8ta7psdoMMeMqK2PJa_SgBzOU-FrpVa6bdfFyhOEa8A@mail.gmail.com>
References:  <CANud0TGz-gG-9TSeWyQcUNXp5=KsNea8qA4vySy_UpsK6Qzv2g@mail.gmail.com> <D321CF65-424D-4397-8473-755D512AF373@freebsd.org> <CANud0TE8ta7psdoMMeMqK2PJa_SgBzOU-FrpVa6bdfFyhOEa8A@mail.gmail.com>

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I was taking a look into the code for rttsample and can we add calling
that rttsample callback at tcp_xmit_timer:
- https://github.com/freebsd/freebsd-src/blob/main/sys/netinet/tcp_input.c#=
L3682

Looks like that place is to calculate t_srtt for TCP stack for feeding
a new RTT from the recent ACK, which seems right for rttsample for
HyStart.

Thanks,
Jaeyong

2025=EB=85=84 3=EC=9B=94 24=EC=9D=BC (=EC=9B=94) =EC=98=A4=ED=9B=84 4:17, j=
aeyong yoo <y.jaeyong@gmail.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> Thanks Cheng,
>
> Yes it looks like it implements newround callback for HyStart.
> But shouldn't it also need for "rttsample" callback?
>
> Thanks,
> Jaeyong
>
> 2025=EB=85=84 3=EC=9B=94 24=EC=9D=BC (=EC=9B=94) =EC=98=A4=ED=9B=84 3:34,=
 Cheng Cui <cc@freebsd.org>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
> >
> >
> >
> > On Mar 20, 2025, at 16:14, jaeyong yoo <y.jaeyong@gmail.com> wrote:
> >
> > Hi net/transport,
> >
> > We are looking for using HyStart but looks like it is only implemented
> > in RACK stack but not in FreeBSD TCP Stack.
> > Is there a plan to support this in the near future?
> >
> > Thanks,
> > Jaeyong
> >
> >
> > Hi Jaeyong,
> >
> > Sorry for the delayed response. There is a patch to enable Hystart++ fo=
r the default TCP stack. If you can help test it, I think it would be very =
helpful to speed up its acceptance.
> >
> > https://reviews.freebsd.org/D46425
> >
> >
> > Best Regards,
> > Cheng Cui
> >
> >
> >



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