From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: TCP connection stops after high load. Date: Wed, 11 Apr 2007 14:06:31 -0700 Message-ID: <461D4DD7.7020207@candelatech.com> References: <461D2DEA.4010806@candelatech.com> <461D447C.4070408@candelatech.com> <20070411.134804.50594117.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from ns2.lanforge.com ([66.165.47.211]:45405 "EHLO ns2.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752689AbXDKVGe (ORCPT ); Wed, 11 Apr 2007 17:06:34 -0400 In-Reply-To: <20070411.134804.50594117.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org David Miller wrote: > From: Ben Greear > Date: Wed, 11 Apr 2007 13:26:36 -0700 > >> Interestingly, I found this page mentioning a SACK problem in Linux: >> http://www-didc.lbl.gov/TCP-tuning/linux.html > > Don't read that page, it is the last place in the world your should > take hints and advice from, most of the problems they speak of there > have been fixed years ago. Much of their memory and buffer settings are similar to what I've seen elsewhere..and what I use, but it could be we're all getting the same info from the same faulty source. Suggestions of a proper site for tuning TCP for high speed/high latency links are welcome. > Please start instrumenting the TCP code instead of "poking around" > hoping you'll hit the grand jackpot by manipulating some sysctl > setting. > > It doesn't help us and it won't help you, start reading and > understanding the TCP code, add debugging printk's, anything to get > more information about this. > > And please don't report anything here until you have some solid piece > of debugging information, else I'll just sit here replying and > prodding you along ever so slowly. :( Does the CWND == 1 count as solid? Any idea how/why this would go to 1 in conjunction with the dup acks? For the dup acks, I see nothing *but* dup acks on the wire...going in both directions interestingly, at greater than 100,000 packets per second. I don't mind adding printks...and I've started reading through the code, but there is a lot of it, and indiscriminate printks will likely just hide the problem because it will slow down performance so much. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com