netdev - Re: [PATCH net-next] tcp: refine tcp_prune_ofo

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Message-ID: <CADVnQy=OVOL_Ffe7UYkvh2fgcXwLQuz40M=+ZVyX-HqCUzQZhg@mail.gmail.com>
Date:   Thu, 18 Aug 2016 15:08:36 -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>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        "C. Stephen Gun" <csg@...gle.com>, Van Jacobson <vanj@...gle.com>
Subject: Re: [PATCH net-next] tcp: refine tcp_prune_ofo_queue() to not drop
 all packets

On Wed, Aug 17, 2016 at 5:17 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> From: Eric Dumazet <edumazet@...gle.com>
>
> Over the years, TCP BDP has increased a lot, and is typically
> in the order of ~10 Mbytes with help of clever Congestion Control
> modules.
>
> In presence of packet losses, TCP stores incoming packets into an out of
> order queue, and number of skbs sitting there waiting for the missing
> packets to be received can match the BDP (~10 Mbytes)
>
> In some cases, TCP needs to make room for incoming skbs, and current
> strategy can simply remove all skbs in the out of order queue as a last
> resort, incurring a huge penalty, both for receiver and sender.
>
> Unfortunately these 'last resort events' are quite frequent, forcing
> sender to send all packets again, stalling the flow and wasting a lot of
> resources.
>
> This patch cleans only a part of the out of order queue in order
> to meet the memory constraints.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Neal Cardwell <ncardwell@...gle.com>
> Cc: Yuchung Cheng <ycheng@...gle.com>
> Cc: Soheil Hassas Yeganeh <soheil@...gle.com>
> Cc: C. Stephen Gun <csg@...gle.com>
> Cc: Van Jacobson <vanj@...gle.com>
> ---

Nice.

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

neal