Date: Thu, 24 Nov 2011 22:22:11 -0600 From: Kris Bauer <kristoph.bauer@gmail.com> To: Lawrence Stewart <lstewart@freebsd.org> Cc: "freebsd-stable@freebsd.org List" <freebsd-stable@freebsd.org> Subject: Re: TCP Reassembly Issues Message-ID: <CAPNZ-WorCriYj8eO5iXyEmSjY1AVKhxCynNxDQOghkuVwqsAVA@mail.gmail.com> In-Reply-To: <4ECF1796.2060107@freebsd.org> References: <CAPNZ-Wq38=F3o2hYuYF_unBj3SZQ52XhVhdcwQ8PE_vU9xc2YA@mail.gmail.com> <CABLqceRyohFFYtdnW%2Bt%2B63kwk00cbkJVz3oXWqrR=xijkg14CA@mail.gmail.com> <4ECE9914.6020502@turing.b2n.org> <CAPNZ-WrQdjFEErt6K1uEndSc082q8Q48VHvtbP=5cNXFw7H7Rg@mail.gmail.com> <1A5B3A48-7DF3-4018-A244-152BDE96299A@lassitu.de> <CAJ-VmokMrJipptQWjuhY5-41p=-P2-xc3ze1p4JKTXWz3MgtzA@mail.gmail.com> <CAPNZ-Wr8r%2Bz7u%2BT3xgY3dfwhEZkN27NebrXzaXmXmneWpMw8xA@mail.gmail.com> <20111125020004.GA36109@icarus.home.lan> <CAPNZ-WraZo9FyvxRyuJ%2BnM2GPoSsqM99L--jOOX=h2VBrPFbHQ@mail.gmail.com> <4ECF1796.2060107@freebsd.org>
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On Thu, Nov 24, 2011 at 10:20 PM, Lawrence Stewart <lstewart@freebsd.org>wrote: > On 11/25/11 14:19, Kris Bauer wrote: > >> On Thu, Nov 24, 2011 at 8:00 PM, Jeremy Chadwick >> <freebsd@jdc.parodius.com>wrote: >> >> On Thu, Nov 24, 2011 at 07:13:39PM -0600, Kris Bauer wrote: >>> >>>> On Thu, Nov 24, 2011 at 5:35 PM, Adrian Chadd<adrian@freebsd.org> >>>> >>> wrote: >>> >>>> >>>> Have you tried disabling the tcp offload features of your NIC? >>>>> >>>>> >>>>> Adrian >>>>> >>>>> >>>> To test this, I added net.inet.tcp.tso=0 to sysctl.conf and restarted >>>> the >>>> box; it didn't work. net.inet.tcp.reass.cursegments immediately started >>>> climbing up and were exhausted within an hour. >>>> >>> >>> I think Adrian was referring to RXCSUM and TXCSUM on your NIC; TSO is >>> another offloading feature. >>> >>> See ifconfig(8) for how to disable those. >>> >>> Be aware that disabling them in real-time (e.g. ifconfig xxx -rxcsum >>> -txcsum) may cause problems; there are some NIC drivers on FreeBSD which >>> do not like you doing this once the NIC has established link (meaning >>> "reloading the driver" (for lack of better term) results in wonky >>> behaviour). So you may instead want to add those hyphen-options to your >>> ifconfig_XXX lines in /etc/rc.conf and reboot the box. >>> >>> If none of this solves the problem, then I consider this a priority 0 >>> blocker (read: "all hands on deck") issue with the IP stack in FreeBSD >>> 9.x and will need immediate attention. >>> >>> I would strongly recommend a developer or clueful end-user begin >>> tracking down who committed all of these bits and CC them into the >>> thread. I would start by looking who implemented the >>> net.inet.tcp.reass.cursegments sysctl, because that isn't in RELENG_8 at >>> all. >>> >>> >> I have added -rxcsum -txcsum -tso to rc.conf and rebooted the box. This >> has not solved the problem. After a half-hour usage, I'm already up to >> reass.cursegments=2182 and it keeps climbing. >> > > This is pretty much guaranteed to be an accounting problem in the TCP > reassembly code (netinet/tcp_reass.c), not a driver related issue. I would > not expect any amount of tweaking, tuning or driver option twiddling to > change the outcome (but if you do find something which alleviates it, do > let us know). > > Kris, are you in a position to test kernel patches on the machine which is > experiencing this problem? > > Cheers, > Lawrence > I'd be happy to test kernel patches with this machine. Thanks, Kris
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