Date: Tue, 2 Aug 2011 14:36:35 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Jack Vogel" <jfvogel@gmail.com> Cc: freebsd-net@freebsd.org, Kevin Oberman <kob6558@gmail.com> Subject: Re: igb enable_aim or flow_control causing tcp stalls? Message-ID: <8F1656993CD14870B678FCF7CF71C113@multiplay.co.uk> References: <379885BA631F4C7787C24E00A174B429@multiplay.co.uk><CAN6yY1s=o=Fd5mgkjrPPqeKmtCXVeDbFrEUqJZk85ccBBa2X4Q@mail.gmail.com><CEE01EEE7538428F8CB9A764CF0EFFFA@multiplay.co.uk><CAFOYbc=2RyTM_SbQt_v96HL_bSwFPmiJqW--tWJUx1x_jM3ffQ@mail.gmail.com> <00F86D895BEA493E8FB82F0CDF42AA04@multiplay.co.uk>
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Wanted to update this thread to confirm, as Jack suspected, the issue we where seeing was something much more ingrained that a driver issue. It turned out this problem in the tcp reassembly code which is likely due to insufficient size of net.inet.tcp.reass.maxsegments. The result is even with just 2 decent sized tcp streams a single lost packet can cause an unrecoverable situation resulting in the session stalling and eventually ~60 seconds later being reset by the sender. Increasing nmbclusters which in turn increases maxsegments eliminated the problem e.g. sysctl kern.ipc.nmbclusters=262144 kern.ipc.nmbclusters: 25600 -> 262144 For more information see the thread:- tcp failing to recover from a packet loss under 8.2-RELEASE? http://lists.freebsd.org/pipermail/freebsd-net/2011-August/029491.html Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.
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