netdev - Re: [PATCH net-next v2 6/6] tcp: SOF_TIMESTAMPING_OPT_STATS option for SO

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Date:   Mon, 28 Nov 2016 12:26:32 -0500
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Yuchung Cheng <ycheng@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        francisyyan@...il.com, Netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next v2 6/6] tcp: SOF_TIMESTAMPING_OPT_STATS option
 for SO_TIMESTAMPING

On Mon, Nov 28, 2016 at 2:07 AM, Yuchung Cheng <ycheng@...gle.com> wrote:
> From: Francis Yan <francisyyan@...il.com>
>
> This patch exports the sender chronograph stats via the socket
> SO_TIMESTAMPING channel. Currently we can instrument how long a
> particular application unit of data was queued in TCP by tracking
> SOF_TIMESTAMPING_TX_SOFTWARE and SOF_TIMESTAMPING_TX_SCHED. Having
> these sender chronograph stats exported simultaneously along with
> these timestamps allow further breaking down the various sender
> limitation.  For example, a video server can tell if a particular
> chunk of video on a connection takes a long time to deliver because
> TCP was experiencing small receive window. It is not possible to
> tell before this patch without packet traces.
>
> To prepare these stats, the user needs to set
> SOF_TIMESTAMPING_OPT_STATS and SOF_TIMESTAMPING_OPT_TSONLY flags
> while requesting other SOF_TIMESTAMPING TX timestamps. When the
> timestamps are available in the error queue, the stats are returned
> in a separate control message of type SCM_TIMESTAMPING_OPT_STATS,
> in a list of TLVs (struct nlattr) of types: TCP_NLA_BUSY_TIME,
> TCP_NLA_RWND_LIMITED, TCP_NLA_SNDBUF_LIMITED. Unit is microsecond.
>
> Signed-off-by: Francis Yan <francisyyan@...il.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> ---

Acked-by: Neal Cardwell <ncardwell@...gle.com>

neal