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Kernel_task on a new MacBook Air

Hi,

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

Posted on Feb 14, 2008 4:42 AM

Reply
209 replies

Feb 19, 2008 1:49 PM in response to zinch

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.

Feb 19, 2008 2:02 PM in response to ralphjjr

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?

Feb 23, 2008 3:56 PM in response to zinch

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

Anyone else seen this? thoughts? The fact that the debug output calls for a true debugging session by apple engineers is worrying.

Mar 6, 2008 10:01 AM in response to ausapple2008

Hi,

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.

Mar 8, 2008 1:54 AM in response to ausapple2008

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?

Mar 11, 2008 8:06 AM in response to Paul Stamatiou

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.

Mar 12, 2008 4:34 AM in response to nrhnrh

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.

Mar 15, 2008 9:35 AM in response to zinch

ok... this issue was getting so irritating i had to search for a forum so i could rant & rave for a bit... my Air shut down about 3 times during the install of windows XP onto the parallel and once after while i was doing multi DL's (adobe illustrator / adobe photoshop & firefox on the XP os).... too much of a work load im assuming... plus the fact that the MBA was SITTING ON THE BED with the rear fans blocking "proper" ventilation could be playing a very large role here.... so the theorys of the core shutting down once they get too hot sounds like something logical... any other thoughts from apple would be best here....
thx for reading

Kernel_task on a new MacBook Air

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