From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mitchell Erblich Subject: Re: TCP not triggering a fast retransmit? Date: Wed, 30 Jun 2010 13:43:41 -0700 Message-ID: <65D4D5A1-78E9-4479-97AF-D2BE598564FD@earthlink.net> References: <9E73042B-BF54-48FD-8755-C215FD03C9AE@earthlink.net> Mime-Version: 1.0 (Apple Message framework v1081) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jmatthews@greenplum.com, Tim Heath To: Ivan Novick Return-path: Received: from elasmtp-scoter.atl.sa.earthlink.net ([209.86.89.67]:43966 "EHLO elasmtp-scoter.atl.sa.earthlink.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753592Ab0F3Uns (ORCPT ); Wed, 30 Jun 2010 16:43:48 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Jun 30, 2010, at 1:14 PM, Ivan Novick wrote: > On Wed, Jun 30, 2010 at 1:06 PM, Mitchell Erblich > wrote: >> On Jun 30, 2010, at 11:04 AM, Ivan Novick wrote: > ... snip ... >> Sometimes, adding tracing within the tcps, can identify if. >> the tcp flow has periods of idleness, >> the tcp flow is/has been application limited versus network limited, >> whether the flow is in SS or CA? >> CA normally has DELayed ACks, which reduces the number >> of ACKs to 1/2 or more, >> Whether Fast re-xmit is triggered by 2 or 3 DupAcks. >> whether any burst avoidance has occured, >> etc, > > Hi Mitchell, > > When you say adding tracing within the tcps... what method are you > referring to, to add this tracing? Is it some tool or setting or are > you talking about adding custom debugging output to the kernel? > > Cheers, > Ivan Ivan, Custom debug code that was added into the fast-path when extensive tcp flow analysis is desired. Uses a runtime /proc var to not effect the fast-path that by default is dis-abled. Mitchell Erblich