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From:   Eric Dumazet <edumazet@google.com>
Date:   Wed, 11 Oct 2023 20:57:18 +0200
Message-ID: <CANn89i+DWa-xbBToc2-Zr2YyZ_axbeo6poyLp9t-XqGr2EzOPA@mail.gmail.com>
Subject: Re: [PATCH net-next,v2] tcp: Set pingpong threshold via sysctl
To:     Haiyang Zhang <haiyangz@microsoft.com>
Cc:     Stephen Hemminger <stephen@networkplumber.org>,
        Yuchung Cheng <ycheng@google.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
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On Wed, Oct 11, 2023 at 8:49=E2=80=AFPM Haiyang Zhang <haiyangz@microsoft.c=
om> wrote:
>
>
>
> > -----Original Message-----
> > From: Stephen Hemminger <stephen@networkplumber.org>
> > Sent: Tuesday, October 10, 2023 10:16 PM
> > To: Haiyang Zhang <haiyangz@microsoft.com>
> > Cc: Yuchung Cheng <ycheng@google.com>; linux-hyperv@vger.kernel.org;
> > netdev@vger.kernel.org; KY Srinivasan <kys@microsoft.com>;
> > davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> > pabeni@redhat.com; corbet@lwn.net; dsahern@kernel.org;
> > ncardwell@google.com; kuniyu@amazon.com; morleyd@google.com;
> > mfreemon@cloudflare.com; mubashirq@google.com; linux-
> > doc@vger.kernel.org; weiwan@google.com; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH net-next,v2] tcp: Set pingpong threshold via sysctl
> >
> > On Tue, 10 Oct 2023 22:59:49 +0000
> > Haiyang Zhang <haiyangz@microsoft.com> wrote:
> >
> > > > > If this an application specific optimization, it should be in a s=
ocket option
> > > > > rather than system wide via sysctl.
> > > > Initially I had a similar comment but later decided a sysctl could
> > > > still be useful if
> > > > 1) the entire host (e.g. virtual machine) is dedicated to that appl=
ication
> > > > 2) that application is difficult to change
> > >
> > > Yes, the customer actually wants a global setting. But as suggested b=
y Neal,
> > > I changed it to be per-namespace to match other TCP tunables.
> >
> > Like congestion control choice, it could be both a sysctl and a socket =
option.
> > The reason is that delayed ack is already controlled by socket options.
>
> I see. I am updating the doc and variable location for this sysctl tunabl=
e patch
> as suggested by the reviewers, and will resubmit it.
>
> I will also work on a separate patch for the setsockopt option.
>
>

I am not sure about adding a socket option, and finding room in the
socket structure.

See our recent effort reshuffling fields in tcp socket for better
performance (stalled at this time).

I would rather experiment first with a sysctl.