From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net 2/2] tcp: fix reordering SNMP under-counting Date: Wed, 05 Apr 2017 18:42:01 -0700 (PDT) Message-ID: <20170405.184201.2156445090158367134.davem@davemloft.net> References: <20170404211540.47887-1-ycheng@google.com> <20170404211540.47887-2-ycheng@google.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, ncardwell@google.com, edumazet@google.com, soheil@google.com To: ycheng@google.com Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:49016 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756315AbdDFBmC (ORCPT ); Wed, 5 Apr 2017 21:42:02 -0400 In-Reply-To: <20170404211540.47887-2-ycheng@google.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Yuchung Cheng Date: Tue, 4 Apr 2017 14:15:40 -0700 > Currently the reordering SNMP counters only increase if a connection > sees a higher degree then it has previously seen. It ignores if the > reordering degree is not greater than the default system threshold. > This significantly under-counts the number of reordering events > and falsely convey that reordering is rare on the network. > > This patch properly and faithfully records the number of reordering > events detected by the TCP stack, just like the comment says "this > exciting event is worth to be remembered". Note that even so TCP > still under-estimate the actual reordering events because TCP > requires TS options or certain packet sequences to detect reordering > (i.e. ACKing never-retransmitted sequence in recovery or disordered > state). > > Signed-off-by: Yuchung Cheng > Signed-off-by: Eric Dumazet > Signed-off-by: Neal Cardwell > Signed-off-by: Soheil Hassas Yeganeh Applied.