From owner-freebsd-net@FreeBSD.ORG Tue Apr 10 22:39:46 2012 Return-Path: Delivered-To: net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 81B201065674; Tue, 10 Apr 2012 22:39:46 +0000 (UTC) (envelope-from julian@freebsd.org) Received: from vps1.elischer.org (vps1.elischer.org [204.109.63.16]) by mx1.freebsd.org (Postfix) with ESMTP id 5C96C8FC0A; Tue, 10 Apr 2012 22:39:46 +0000 (UTC) Received: from julian-mac.elischer.org (c-67-180-24-15.hsd1.ca.comcast.net [67.180.24.15]) (authenticated bits=0) by vps1.elischer.org (8.14.5/8.14.5) with ESMTP id q3AMdcnO035453 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Tue, 10 Apr 2012 15:39:40 -0700 (PDT) (envelope-from julian@freebsd.org) Message-ID: <4F84B6DB.5040904@freebsd.org> Date: Tue, 10 Apr 2012 15:40:27 -0700 From: Julian Elischer User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10.4; en-US; rv:1.9.2.28) Gecko/20120306 Thunderbird/3.1.20 MIME-Version: 1.0 To: Luigi Rizzo References: <20120410225257.GB53350@onelab2.iet.unipi.it> In-Reply-To: <20120410225257.GB53350@onelab2.iet.unipi.it> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: current@freebsd.org, net@freebsd.org Subject: Re: strange ping response times... X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Apr 2012 22:39:46 -0000 On 4/10/12 3:52 PM, Luigi Rizzo wrote: > I noticed this first on a 10G interface, but now there seems > to be a similar issue on the loopback. > > Apparently a ping -f has a much lower RTT than one with non-zero > delay between transmissions. Part of the story could be that > the flood version invokes a non-blocking select. > On the other hand, pinging on the loopback should make > the response available right away, so what could be the reason > for the additional 3..10us in the ping response time ? > > The following are numbers on an i7-2600k at 3400 MHz + turboboost, > running stable/9 amd64. Note how the min ping time significantly > increases moving from flood to 10ms to 1s. > On an Intel 10G interface i am seeing a min of 14-16us with > a ping flood, and up to 33-35us with the standard 1s interval > (using -q probably trims another 2..5us) I'd suggest some ktr points around the loopback path.. > > sudo ping -c 1000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.003/0.012/0.001 ms > > sudo ping -c 1000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.002/0.013/0.001 ms > > sudo ping -c 1000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.002/0.013/0.001 ms > > sudo ping -c 10000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.002/0.011/0.001 ms > > > sudo ping -c 1000 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.005/0.012/0.017/0.001 ms > > sudo ping -c 1000 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.004/0.012/0.016/0.001 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.012/0.017/0.002 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.005/0.012/0.018/0.002 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.009/0.012/0.020/0.002 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.006/0.012/0.016/0.001 ms > > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.014/0.020/0.001 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.006/0.014/0.019/0.002 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.014/0.021/0.001 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.014/0.020/0.001 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.006/0.014/0.021/0.002 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.010/0.014/0.022/0.001 ms > > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.013/0.018/0.022/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.012/0.018/0.021/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.009/0.017/0.018/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.011/0.017/0.021/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.010/0.017/0.020/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.009/0.017/0.028/0.004 ms > > cheers > luigi > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >