netdev - Re: [PATCH net-next] tcp: tso: allow deferring under reordering state

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Message-ID: <CADVnQynorgXVLwfqHL+3vmLjVk_CriX8ob+GZHwS9BqpKsA8Uw@mail.gmail.com>
Date:	Sun, 26 Jul 2015 11:43:39 -0400
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH net-next] tcp: tso: allow deferring under reordering state

On Sun, Jul 26, 2015 at 3:45 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> While doing experiments with reordering resilience, we found
> linux senders were not able to send at full speed under reordering,
> because every incoming SACK was releasing one MSS.
>
> This patch removes the limitation, as we did for CWR state
> in commit a0ea700e409 ("tcp: tso: allow CA_CWR state in
> tcp_tso_should_defer()")
>
> Neal Cardwell had a concern about limited transmit so
> Yuchung conducted experiments on GFE and found nothing
> worth adding an extra check on fast path :
>
>   if (icsk->icsk_ca_state == TCP_CA_Disorder &&
>       tcp_sk(sk)->reordering == sysctl_tcp_reordering)
>           goto send_now;
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Cc: Neal Cardwell <ncardwell@...gle.com>

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

Looks good to me. Thanks, Eric. And thanks, Yuchung, for running the experiment!

neal
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