8 Replies Latest reply: Jul 24, 2013 3:48 AM by Velile
r.d Level 1 Level 1 (0 points)

Hi, I have a Mac Mini (2GHz Core 2 Duo, 4GB ram and Lion 10.7.3) that I'm using as a server and home theater pc. I leave it running 24 hours a day and it hosts a Plex server, Transmission (Bit Torrent client) and time machine backups. I also run an Air Video server and Mobile Mouse Pro server (for control using my iPhone). Lately the machine has slowed to a crawl making it completely unusable until I reboot. After a reboot, it will run fine for a few days then slow again. In activity moniter, I can see syslogd using 100% of the cpu. From what I understand, syslogd is the error reporting function in the console. When I check the console, I see this message spamming 500+ times every second:


1/28/12 2:06:35.025 PM mDNSResponder: mDNS_Deregister_internal:   21 6.8.0.E.D.5.E.F.F.F.A.C.5.5.A. PTR Apple-TV-2116.local. already marked kDNSRecordTypeDeregistering

1/28/12 2:06:35.025 PM mDNSResponder: *** process 14 exceeded 500 log message per second limit  -  remaining messages this second discarded ***



From what I understand, mDNSResponder is related to Bonjour and can be disabled but this is the one machine on the network that I actually want Bonjour enabled (screen sharing and transmission web ui). I have four other Macs on the network and this is the only one having this problem. I also have a jailbroken AppleTV on the network that runs a Plex client to watch my content on the other TV in the house. If I unplug the AppleTV during the slow down, it doesn't stop the spamming. I also wonder about calling it "Apple-TV-2116.local" in the console because when I ssh into the AppleTV to update apps, it's address is simply "Apple-TV.local".


I disabled sleep on the AppleTV because I thought it was getting a new address/ip everytime it woke but that hasn't stopped the issue. I googled the error and only found one other forum post regarding the issue and there was no solution. I'm tempted to take the AppleTV off the network for a week to see if that resolves the issue but it does get used fairly often and none of the other macs on the network are having problems so I think it's something specific to my mac mini.




  • 1. Re: syslogd using 100% CPU logging mDNSResponder error
    Linc Davis Level 10 Level 10 (117,840 points)

    Remove the jailbreak on the ATV, or turn it off. Same problem?

  • 2. Re: syslogd using 100% CPU logging mDNSResponder error
    jonhughes1 Level 1 Level 1 (0 points)

    I have the same issue - Apple TV isn't jailbroken though.


    Apple TV 1080p

    Macbook Pro (mid 2009 - MacbookPro5,3) running Lion, all updates installed

    Airport Extreme running firmware 7.6.1


    Also on the network:

    Mac mini (mid 2010 - Macmini4,1) - also up to date on Lion (NOT having the mDNSresponder CPU issue)

    iPhone 4S & iPad 2, both running iOS 5.1

    Drobo FS

    Cable TV box

  • 3. Re: syslogd using 100% CPU logging mDNSResponder error
    metaxis Level 1 Level 1 (0 points)

    I am also seeing this problem, as of installing the brand new Apple TV.  My mac mini running 10.7 gets rate limited syslog entries, with each of mDNSresponder and syslogd taking a core, hummm....


    2012.04.14 11:50:33.024 AM mDNSResponder: mDNS_Deregister_internal:   <ipv6addr>.ip6.arpa. PTR Apple-TV-578.local. already marked kDNSRecordTypeDeregistering


    Killing off mDNSResponder stops it, for a while.  I don't know what causes it to start up again.  I'd love a solution, as it looks like a bug with mDNSResponder itself, rather than a configuration issue with my mac, apple tv, or network.


    Both are very plain vanilla from a config and software standpoint (no jail breaking, haxoring, etc) and updated to current versions of soft/firmware.


    I don't want to disable Bonjour, I use it.  Obviously the problem is related to the Apple TV device, but according to the message above, there is some sort of internal argument about whether or not an IP v6 addr is in the correct state/workflow.  Whatevs.  I could probably disable ipv6 and forget it, but that's not really a fix, more of a field dressing.  At this point, IPv6 needs to work, bonjour needs to work, even with a misbehaving device.


    Looking at the responses I'm not seeing that a community response is likely on this obscure little corner of tech.  So, what next?

  • 4. Re: syslogd using 100% CPU logging mDNSResponder error
    mvogiatzis Level 1 Level 1 (0 points)


    This happens very frequently. I return home after many hours, and sometimes find my laptop's fans screaming !!!! Apple should fix that !!!! 10.7.4 13" macbook pro 2012 (2.8 i7). Also, the problem can be reproduced if I am connected for a long time to vpn connection. In general, this happens when the system fails to sleep after the threshold of time that I have configured inside power settings.... What may cause this problem ?

  • 5. Re: syslogd using 100% CPU logging mDNSResponder error
    ahuisman Level 1 Level 1 (0 points)

    Having exactly the same issue, MacBook Pro (early 2011) running Mac OS X Lion 10.7.4 (and all other patches and firmware updates that are available), also having an Apple TV (2nd generation also running the latest iOS version).


    There's also an iPad, 2 iPhones, a Time Capsule (latest 1 TB model) and a MacBook from 2008 on the network (still running 10.6 with the latest updates installed). This laptop isn't experiencing any mDNSResponder CPU issue at all.


    Rebooted the Apple TV yesterday but that didn't help.


    When I use my laptop at home the CPU goes up to 100% for mDNSResponder quite some times a day (even when the laptop is closed and thus standby). Killing it helps.


    When I use my laptop in the office it doesn't happen at all, so it's apparently a combination of Lion in combination with my home network or devices on it (router is a Fritz!Box 7390, the Time Capsule is only being used for backups).

  • 6. Re: syslogd using 100% CPU logging mDNSResponder error
    r.d Level 1 Level 1 (0 points)

    I fixed this problem a few weeks after my original post by reinstalling the OS on the machine. Not the best solution but it was pretty quick because the computer is used as a homeserver/media center so it only took a few hours to reconfigure.


    One thing I tried before reinstalling was unplugging my AppleTV, restarting my mac mini and seeing if the problem reappeared. It did. I don't really understand the issue, it seems like most of us have a network with mutliple macs (one with a syslogd problem) and an AppleTV.


    I was using a Belkin router unlike some of the other people so I don't think it is related to the router -at least the brand anyway.


    Good luck guys, I hope you find a simpler solution than I did.

  • 7. Re: syslogd using 100% CPU logging mDNSResponder error
    mvogiatzis Level 1 Level 1 (0 points)

    Well my experience for the above screenshot, has nothing to do with wireless. When this appears, the laptop is connected using ethernet over the internet, and internet sharing tethering to other portable devices is switched off.

  • 8. Re: syslogd using 100% CPU logging mDNSResponder error
    Velile Level 1 Level 1 (0 points)

    I have the same issue:  mDNS runs up to 90% cpu, fans are screaming, internet stops working.  The temp solution is to kill the mDNS process via ACTIVITY MONITOR .  When I look at CONSOLE I see following error message over and over again:


    mDNSResponder: ip6 mDNS_Deregister_internal PTR Apple-TV-27336.local. already marked kDNSRecordTypeDeregistering


    So it seems to be something to do with Apple TV when I am at home.  But this also happens when I am travelling.  I'll check what error message I get then and post it.

    I also flush the mDNS cache with


    sudo killall -HUP mDNSResponder

    but that doesn't stop  mDNS from overloading again.

    I'd appreciate help on getting mDNS to behave normally.