From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: Re: [PATCH net-next 1/2] tcp_cubic: add SNMP counters to track how effective is Hystart Date: Fri, 5 Dec 2014 01:17:54 +0100 Message-ID: <20141205001754.GG16959@breakpoint.cc> References: <1417738403.22424.28.camel@edumazet-glaptop2.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , netdev , Nandita Dukkipati , Neal Cardwell , Yuchung Cheng , Sangtae Ha To: Eric Dumazet Return-path: Received: from Chamillionaire.breakpoint.cc ([80.244.247.6]:39880 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752093AbaLEAR5 (ORCPT ); Thu, 4 Dec 2014 19:17:57 -0500 Content-Disposition: inline In-Reply-To: <1417738403.22424.28.camel@edumazet-glaptop2.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: Eric Dumazet wrote: > When deploying FQ pacing, one thing we noticed is that CUBIC Hystart > triggers too soon. > > Having SNMP counters to have an idea of how often the various Hystart > methods trigger is useful prior to any modifications. > > This patch adds SNMP counters tracking, how many time "ack train" or > "Delay" based Hystart triggers, and cumulative sum of cwnd at the time > Hystart decided to end SS (Slow Start) > > myhost:~# nstat -a | grep Hystart > TcpExtTCPHystartTrainDetect 9 0.0 > TcpExtTCPHystartTrainCwnd 20650 0.0 > TcpExtTCPHystartDelayDetect 10 0.0 > TcpExtTCPHystartDelayCwnd 360 0.0 > > -> > Train detection was triggered 9 times, and average cwnd was > 20650/9=2294, > Delay detection was triggered 10 times and average cwnd was 36 Alternatively we could add INET_DIAG_CUBICINFO and export such info via ss tool.