linux-kernel - Re: [PATCH net-next,v2] tcp: Set pingpong threshold via sysctl

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Message-ID: <CANn89i+DWa-xbBToc2-Zr2YyZ_axbeo6poyLp9t-XqGr2EzOPA@mail.gmail.com>
Date:   Wed, 11 Oct 2023 20:57:18 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "dsahern@...nel.org" <dsahern@...nel.org>,
        "ncardwell@...gle.com" <ncardwell@...gle.com>,
        "kuniyu@...zon.com" <kuniyu@...zon.com>,
        "morleyd@...gle.com" <morleyd@...gle.com>,
        "mfreemon@...udflare.com" <mfreemon@...udflare.com>,
        "mubashirq@...gle.com" <mubashirq@...gle.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "weiwan@...gle.com" <weiwan@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next,v2] tcp: Set pingpong threshold via sysctl

On Wed, Oct 11, 2023 at 8:49 PM Haiyang Zhang <haiyangz@...rosoft.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Stephen Hemminger <stephen@...workplumber.org>
> > Sent: Tuesday, October 10, 2023 10:16 PM
> > To: Haiyang Zhang <haiyangz@...rosoft.com>
> > Cc: Yuchung Cheng <ycheng@...gle.com>; linux-hyperv@...r.kernel.org;
> > netdev@...r.kernel.org; KY Srinivasan <kys@...rosoft.com>;
> > davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> > pabeni@...hat.com; corbet@....net; dsahern@...nel.org;
> > ncardwell@...gle.com; kuniyu@...zon.com; morleyd@...gle.com;
> > mfreemon@...udflare.com; mubashirq@...gle.com; linux-
> > doc@...r.kernel.org; weiwan@...gle.com; linux-kernel@...r.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@...rosoft.com> wrote:
> >
> > > > > If this an application specific optimization, it should be in a socket 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 application
> > > > 2) that application is difficult to change
> > >
> > > Yes, the customer actually wants a global setting. But as suggested by 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 tunable 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.