netdev - Re: [RFC PATCH] tcp: correct srtt and mdev

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Message-ID: <20221211090456.652eda22@hermes.local>
Date:   Sun, 11 Dec 2022 09:04:56 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Jakub Sitnicki <jakub@...udflare.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Weiping Zhang <zhangweiping@...iglobal.com>,
        davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        zwp10758@...il.com
Subject: Re: [RFC PATCH] tcp: correct srtt and mdev_us calculation

On Sat, 10 Dec 2022 18:45:56 +0100
Eric Dumazet <edumazet@...gle.com> wrote:

> On Tue, Dec 6, 2022 at 10:29 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
> 
> 
> > Nifty. And it's documented.
> >
> > struct tcp_sock {
> >         …
> >         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
> >
> > Thanks for the hint.  
> 
> The >> 3 is all over the place... So even without a formal comment,
> anyone familiar with TCP stack would spot this...

And it should be in every text book already and is in BSD as well.
Maybe a link to the SIGCOMM paper would be good for those
google deprived people?