netdev - Re: [PATCH 1/3] Add TX sending hardware timestamp.

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Message-ID: <CA+FuTScWkYn0Ur+aSuz1cREbQJO0fB6powOm8PFxze4v8JwBaw@mail.gmail.com>
Date:   Wed, 9 Dec 2020 09:48:53 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Erez Geva <erez.geva.ext@...mens.com>
Cc:     Network Development <netdev@...r.kernel.org>,
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        Erez Geva <ErezGeva2@...il.com>
Subject: Re: [PATCH 1/3] Add TX sending hardware timestamp.

On Wed, Dec 9, 2020 at 9:37 AM Erez Geva <erez.geva.ext@...mens.com> wrote:
>
> Configure and send TX sending hardware timestamp from
>  user space application to the socket layer,
>  to provide to the TC ETC Qdisc, and pass it to
>  the interface network driver.
>
>  - New flag for the SO_TXTIME socket option.
>  - New access auxiliary data header to pass the
>    TX sending hardware timestamp.
>  - Add the hardware timestamp to the socket cookie.
>  - Copy the TX sending hardware timestamp to the socket cookie.
>
> Signed-off-by: Erez Geva <erez.geva.ext@...mens.com>

Hardware offload of pacing is definitely useful.

I don't think this needs a new separate h/w variant of SO_TXTIME.

Indeed, we want pacing offload to work for existing applications.

It only requires that pacing qdiscs, both sch_etf and sch_fq,
optionally skip queuing in their .enqueue callback and instead allow
the skb to pass to the device driver as is, with skb->tstamp set. Only
to devices that advertise support for h/w pacing offload.