From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: problems achieving decent throughput with latency. Date: Sat, 01 Feb 2003 14:13:01 -0800 Sender: netdev-bounce@oss.sgi.com Message-ID: <3E3C466D.7030602@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: "'netdev@oss.sgi.com'" Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org I am testing my latency-insertion tool, and I notice that tcp will not use all of the available bandwidth if there is any significant amount of latency on the wire. For example, with 25ms latency in both directions, I see about 8Mbps bi-directional throughput. If I lower that to 15ms, I see 12Mbps bi-directional throughput. I see 27Mbps at 5ms. Here is the /proc/net/tcp output at 5ms latency. machine demo2 13: 050302AC:80EB 070302AC:80EB 01 0005900C:0002012E 01:00000016 00000000 0 0 578943 3 c6628a80 22 4 1 45 -1 machine demo1 11: 070302AC:80EB 050302AC:80EB 01 00010DDB:00000000 01:00000014 00000000 0 0 513094 3 c62c5080 21 4 1 45 -1 Any ideas why it is so slow at the higher latencies? Any other info I can gather to help determine the cause? (UDP does not experience this slowdown, so I believe my latency insertion tool is working as designed, but it's always possible it is to blame...) -- Ben Greear President of Candela Technologies Inc http://www.candelatech.com ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear