From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] tcp: switch snt_synack back to measuring transmit time of first SYNACK Date: Mon, 07 Jul 2014 19:26:52 -0700 (PDT) Message-ID: <20140707.192652.2078847253054450980.davem@davemloft.net> References: <1404155389-22927-1-git-send-email-ncardwell@google.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, ycheng@google.com, octavian.purdila@intel.com, hkchu@google.com To: ncardwell@google.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:48302 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752230AbaGHC0x (ORCPT ); Mon, 7 Jul 2014 22:26:53 -0400 In-Reply-To: <1404155389-22927-1-git-send-email-ncardwell@google.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Neal Cardwell Date: Mon, 30 Jun 2014 15:09:49 -0400 > Always store in snt_synack the time at which the server received the > first client SYN and attempted to send the first SYNACK. > > Recent commit aa27fc501 ("tcp: tcp_v[46]_conn_request: fix snt_synack > initialization") resolved an inconsistency between IPv4 and IPv6 in > the initialization of snt_synack. This commit brings back the idea > from 843f4a55e (tcp: use tcp_v4_send_synack on first SYN-ACK), which > was going for the original behavior of snt_synack from the commit > where it was added in 9ad7c049f0f79 ("tcp: RFC2988bis + taking RTT > sample from 3WHS for the passive open side") in v3.1. > > In addition to being simpler (and probably a tiny bit faster), > unconditionally storing the time of the first SYNACK attempt has been > useful because it allows calculating a performance metric quantifying > how long it took to establish a passive TCP connection. > > Signed-off-by: Neal Cardwell > Signed-off-by: Yuchung Cheng Applied, thanks.