Date: Tue, 27 Mar 2018 14:48:29 +0000 From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: "Kristof Provost" <kristof@sigsegv.be> Cc: "Reshad Patuck" <reshad@patuck.net>, "FreeBSD Net" <freebsd-net@freebsd.org> Subject: Re: [vnet] [epair] epair interface stops working after some time Message-ID: <2D15ABDE-0C25-4C97-AEA6-0098459A2795@lists.zabbadoz.net> In-Reply-To: <7202AFF2-A314-41FE-BD13-C4C77A95E106@sigsegv.be> References: <CADaJeD2LZy=RU0vtqD7%2BdkZkUs0GKW%2B7duGDQkZ19GR-_cS=MQ@mail.gmail.com> <71B1A1BD-6FCF-47BB-9523-CCAAC03799A5@sigsegv.be> <1563563.7DUcjoHYMp@reshadlaptop.patuck.net> <C162AFB2-FF80-4640-BDC8-23B30CC22873@sigsegv.be> <1D6101CD-BCB4-4206-838B-1A75152ACCC4@sigsegv.be> <AB52ED81-F97F-471B-A1BA-F3221152A586@patuck.net> <F382A5B4-6941-43C0-9686-4B108034EBF1@patuck.net> <FDCE9FAA-1289-4E15-9239-1B6FD98B589C@sigsegv.be> <38C78C2B-87D2-4225-8F4B-A5EA48BA5D17@patuck.net> <5803CAA2-DC4A-4E49-B715-6DE472088DDD@sigsegv.be> <9CAB4522-0B0A-42BF-B9A4-BF36AFC60286@patuck.net> <7202AFF2-A314-41FE-BD13-C4C77A95E106@sigsegv.be>
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On 27 Mar 2018, at 14:40, Kristof Provost wrote: > (Re-cc freebsd-net, because this is useful information) > > On 27 Mar 2018, at 13:07, Reshad Patuck wrote: >> The epair crash occurred again today running the epair module code >> with the added dtrace sdt providers. >> >> Running the same command as last time, 'dtrace -n ::epair\*:' returns >> the following: >> ``` >> CPU ID FUNCTION:NAME > … >> 0 66499 epair_transmit_locked:enqueued >> ``` > >> Looks like its filled up a queue somewhere and is dropping >> connections post that. >> >> The value of the 'error' is 55 I can see both the ifp and m structs >> but don't know what to look for in them. >> > That’s useful. Error 55 is ENOBUFS, which in IFQ_ENQUEUE() means > we’re hitting _IF_QFULL(). > There don’t seem to be counters for that drop though, so that makes > it hard to diagnose without these extra probe points. > It also explains why you don’t really see any drop counters > incrementing. > > The fact that this queue is full presumably means that the other side > is not reading packets off it any more. > That’s supposed to happen in epair_start_locked() (Look for the > IFQ_DEQUEUE() calls). > > It’s not at all clear to my how, but it looks like the receive side > is not doing its work. > > It looks like the IFQ code is already a fallback for when the netisr > queue is full. > That code might be broken, or there might be a different issue that > will just mean you’ll always end up in the same situation, > regardless of queue size. > > It’s probably worth trying to play with > ‘net.route.netisr_maxqlen’. I’d recommend *lowering* it, to see > if the problem happens more frequently that way. If it does it’ll be > helpful in reproducing and trying to fix this. If it doesn’t the > full queues is probably a consequence rather than a cause/trigger. > (Of course, once you’ve confirmed that lowering the netisr_maxqlen > makes the problem more frequent go ahead and increase it.) netstat -Q will be useful
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