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zinch Level 1 (0 points)

I bought my MacBook Air a few days ago and am very pleased at how well it runs... except when it doesn't. In the course of using the computer, all of a sudden things will get very slow and the mouse and keyboard will barely respond. The mouse moves erratically and keypresses take a while to show up.

Opening up Activity Monitor shows that kernel_task is taking up 50%+ of the CPU. I've tried to isolate any programs that may be doing it. Shutting down iTunes now seemed to have bring kernel_task back down and the system responsive. But other times it doesn't.

Is this is a known bug? Can someone point me in the direction of a solution?

MacBook Air, Mac OS X (10.5.2), None
  • zinch Level 1 (0 points)
    Looking through the forum this is not unusual but I can't see a solution - anyone?!
  • nrhnrh Level 1 (0 points)
    I have the same problem.
    I've noticed that the computer drops down to one core when this happens.
  • Rhyd Level 3 (795 points)
    Open Console from utilities folder and check both the console log and the system log to see what has been happening. Activity Monitor and console together should give you a better picture of what is happening and has happened.
  • noaml Level 1 (0 points)
    Same thing happens to me. Usually starts happening when I copy something to the drive or start installing something. Basically renders the machine unusable.
  • ralphjjr Level 1 (0 points)
    I've been having the exact same problem and have been testing a variety of configurations to pinpoint what the issue could be. Besides "using" the MBA, is there anything special about what you are doing?
    For exampe, are you using a bluetooth keyboard and/or mouse? Are you using the USB Ethernet Adapter and/or a mini-DVI plug going to a monitor?

    As a side note, check out this question: Performance "throttle back" problem
    Brian Caslis' response: +"Yes, it's true if it gets really hot one core shuts off to reduce temperature."+
    This may very well be what is happening. One core gets shut off and the system just doesn't know how to handle itself with a single core. That's a lame explanation, I know, but it does explain the issue. Although, there has to be something we can do, short of purchasing a notebook cooler, that will not cause this to happen every single time we are doing "a lot" of work.
  • ralphjjr Level 1 (0 points)
    I'm going to roll with my own explanation, it sounded lame at first, but I think I can verbalize it better.

    I'm going to run with the theory that temperature is causing this issue. Heavy processing can cause the temperature of the machine to rise and thus, in an effort to save the core(s) the MBA shuts off one of the cores. This is a normal thing for CPUs, if a CPU gets "too" hot it must save itself from utter damage and shut itself off. This, unfortunately, seems to cause a vicious cycle: the shutting off of one core forces all the work on the remaining core, this means the temperature will not get back to normal on its own. The user is forced to close I/O or CPU intensive applications, this slowly brings the temperature down and allows the core that shut off to be turned back on.

    Improper heat dissipation may add to the problem. If your MBA is closed (because you are using an external keyboard and bluetooth keyboard and mouse), heat cannot dissipate properly. The heat vents are on the bottom, in the rear of the MBA, perhaps they are blocked by something and thus adding to poor heat dissipation.

    This is totally a theory. Any thoughts?
  • nrhnrh Level 1 (0 points)
    that's what I thought too, but when it gets in this state the cooling fan is not running, which makes me think it's something else.

    also, i've noticed that shutting the lid/inducing sleep and restarting immediately fixes this issue.
  • blindmull Level 1 (0 points)
    i can confirm kernel_task taking up almost 50% cpu on my powerbook, running 10.5.2, making the pb VERY slow. it happened while i was checking e-mail...
    after rebooting everything's back to normal, kernel_task taking taking up between 1,5 to 3 % of cpu.
  • ausapple2008 Level 1 (0 points)
    So, i'm stuck in the same situation: the air gets too slow to even keep up with keystrokes or mouse movements. Great!

    One thing I have seen in the console is that syslog / launchd mysteriously fail on various tasks. See the log below:

    Feb 24 10:35:09 personal-macbook-air[1] ([17]): Exited abnormally: Bus error
    Feb 24 10:35:38 personal-macbook-air[1] ([345]): Exited abnormally: Bus error
    Feb 24 10:41:08 personal-macbook-air[351]: syslogd(351,0xa0978fa0) malloc: * mmap(size=3606249472) failed (error code=12)
    Feb 24 10:41:08 personal-macbook-air[351]: * error: can't allocate region
    Feb 24 10:41:08 personal-macbook-air[351]: * set a breakpoint in mallocerrorbreak to debug
    Feb 24 10:41:41 personal-macbook-air[351]: syslogd(351,0xa0978fa0) malloc: * mmap(size=3606249472) failed (error code=12)
    Feb 24 10:41:41 personal-macbook-air[351]: * error: can't allocate region
    Feb 24 10:41:41 personal-macbook-air[351]: * set a breakpoint in mallocerrorbreak to debug

    Anyone else seen this? thoughts? The fact that the debug output calls for a true debugging session by apple engineers is worrying.
  • ausapple2008 Level 1 (0 points)
    Does anyone in this thread use an external monitor with their Air?
  • zinch Level 1 (0 points)

    I can confirm I'm using an external monitor most of the time - but I'm on the road at the moment without one and it's still happening. I'm also without my usual bluetooth keyboard and mouse.

    I liked the temperature theory so I installed a piece of software that monitors the temperature of the CPUs - while it gets high when the kernel_task process goes crazy, it's just as high at other times when the computer runs perfectly.

    Apple, please help! There are quite a few people reporting this issue now.
  • Paul Stamatiou Level 1 (10 points)
    I use a 24-inch external monitor with my MBA most of the time. I also have this kernel_task problem and it's annoying! I think i've narrowed down the cause to network issues. I almost always get it when interacting with my NAS/xferring files and sometimes when saving files to FTP. Maybe it comes down to a buggy Wi-Fi driver kernel extension?
  • Cottonwood1162 Level 1 (0 points)
    I had the same problem on my MBA this morning. I had been using a 24" external monitor, but had disconnected it. Also, I was using the USB-EtherNet adapter. Sometime later, the kernel_task went to over 70% and the MBA was running on one CPU; it was almost unusable. I tried rebooting (took a while) and the problem persisted. After reading these posts, I unplugged the USB-EtherNet adapter and the kernel_task usage immediately dropped to normal, and the MBA started using both CPUs again. I turned on Airport, no problem, then turned it off, no problem, then plugged the USB-EtherNet adapter back in, no problem.

    At this point, I cannot recreate the problem, but unplugging the USB-EtherNet adapter seems to have stopped it.
  • zinch Level 1 (0 points)
    Right, some more information - I can confirm that when the performance degredation happens it's indeed followed by the stoppage of one of the cores (in Activity Monitor the bottom CPU usage box is black with no activity). Closing the lid and reopening it fixes the problem immediately.

    The temperature monitor software has the temperature at around 65c the entire time, and the fans are not spinning much harder than normal.

    Apple, please acknowledge this issue and do something about it! It happens a lot when time machine kicks in during normal operation.
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