From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] tcp: refine tcp_prune_ofo_queue() to not drop all packets Date: Thu, 18 Aug 2016 23:36:43 -0700 (PDT) Message-ID: <20160818.233643.732250691565806768.davem@davemloft.net> References: <1471468629.29842.39.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, soheil@google.com, ncardwell@google.com, ycheng@google.com, csg@google.com, vanj@google.com To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:42454 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753413AbcHSGhR (ORCPT ); Fri, 19 Aug 2016 02:37:17 -0400 In-Reply-To: <1471468629.29842.39.camel@edumazet-glaptop3.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Wed, 17 Aug 2016 14:17:09 -0700 > From: Eric Dumazet > > 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 Looks great, applied.