netdev - Re: [PATCH net-next v2 4/6] tcp: instrument how long TCP is limited by insufficient send buffer

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Message-ID: <CADVnQy=VhKubFx4yLwYAbYUieB57rB4sr27jhrKtnjgwxqzMig@mail.gmail.com>
Date:   Mon, 28 Nov 2016 12:25:36 -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 4/6] tcp: instrument how long TCP is limited
 by insufficient send buffer

On Mon, Nov 28, 2016 at 2:07 AM, Yuchung Cheng <ycheng@...gle.com> wrote:
> From: Francis Yan <francisyyan@...il.com>
>
> This patch measures the amount of time when TCP runs out of new data
> to send to the network due to insufficient send buffer, while TCP
> is still busy delivering (i.e. write queue is not empty). The goal
> is to indicate either the send buffer autotuning or user SO_SNDBUF
> setting has resulted network under-utilization.
>
> The measurement starts conservatively by checking various conditions
> to minimize false claims (i.e. under-estimation is more likely).
> The measurement stops when the SOCK_NOSPACE flag is cleared. But it
> does not account the time elapsed till the next application write.
> Also the measurement only starts if the sender is still busy sending
> data, s.t. the limit accounted is part of the total busy time.
>
> 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