Re: [PATCH net-next] tcp: refine tcp_prune_ofo_queue() to not drop all packets

[David Miller <davem@davemloft.net>]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 17 Aug 2016 14:17:09 -0700

> From: Eric Dumazet <edumazet@google.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@google.com>

Looks great, applied.