Skip navigation

kernel_task on CPU, MacPro

439 Views 8 Replies Latest reply: Mar 3, 2013 8:34 PM by Linc Davis RSS
lundman Level 1 Level 1 (0 points)
Currently Being Moderated
Jan 7, 2013 4:15 PM

Plenty of threads on the kernel_task issue, even here. But most of them are on MacBooks, and seem to think it is heat related. I see this issue twice a month or so, on a MacPro.




# top -u


kernel_task  400.7 109 hrs  91/12 073725M0B 1018M
54170  top      21.5  00:00.63 1/1   024+36+3056K+ 220K-  3812K+
22871  seamonkey12.1  05:40:20 31/1  3363-   18285- 754M-  156M-  1176M-
50207- iTerm    9.9   18:26:24 8/2   4171-   383-   36M-   28M-   65M-



Brendans hotkernel say:


mach_kernel`pmap_remove_range                           8   0.1%
mach_kernel`0xffffff801a921080                         10   0.1%
mach_kernel`lck_mtx_lock                               22   0.2%
mach_kernel`pmap_flush_tlbs                            37   0.4%
mach_kernel`_rtc_nanotime_read                         55   0.6%
mach_kernel`machine_idle                             4182  42.3%
mach_kernel`ml_set_interrupts_enabled                5408  54.7%
  • XENiCraft Level 2 Level 2 (210 points)
    Currently Being Moderated
    Jan 7, 2013 4:33 PM (in response to lundman)

    Could you please provide a screenshot of where you see this in activity monitor?

  • Linc Davis Level 10 Level 10 (108,150 points)
    Currently Being Moderated
    Jan 7, 2013 6:26 PM (in response to lundman)

    The kernel is using excessive processor cycles. Below is a partial list of causes for this condition.

    Thermal overload

    This can be due to accumulation of dust, high ambient temperature, or to the malfunction of a cooling fan or temperature sensor. The kernel tries to compensate by throttling back the CPU's. You might see messages like the following in the Console window:

    SMC::smcHandleInterruptEvent WARNING status=0x0 (0x40 not set) notif=0x0

    The timestamps of those messages (if any) indicate the times, since the log was last cleared, when a processor was being throttled because of high temperature.

    Note that if the problem is caused by a faulty sensor that reads too high, there may be no actual overheating.

    The Apple Hardware Test, though not very reliable, is sometimes able to detect a bad fan or temperature sensor.

    Using Apple Hardware Test



    Transferring large amounts of data to or from an encrypted disk image or FileVault volume puts an extra load on the kernel. If both the source and the destination are encrypted, the load may be doubled. If you transfer data from an encrypted disk image on an encrypted partition to another such image on another encrypted partition, the load may be quadrupled.

    This issue probably doesn't affect late-model Macs with an Intel i-series, recent Xeon, or later processor. Those processors support hardware-accelerated encryption. You can determine what kind of processor you have by selectingAbout This Mac from the Apple menu in the menu bar.

    Installed software

    User-installed software that includes a device driver or other kernel code may thrash the kernel. Some system-monitoring applications, such as "iStat," can also contribute to the problem. You can test for this possibility bycompletely disabling or removing the software according to the developer's instructions, or booting in safe mode (with the shift key held down at the startup chime.) Note, however, that disabling a system modification without removing it or booting in safe mode may not be as easy as you think it is.

    Corrupt NVRAM or SMC data

    In some cases the issue has reportedly been resolved by resetting the NVRAM or the SMC.

  • Linc Davis Level 10 Level 10 (108,150 points)
    Currently Being Moderated
    Mar 3, 2013 8:03 PM (in response to lundman)

    You have at least two system modifications that could be contributing to the problem: VirtualBox and Viscosity.

  • Linc Davis Level 10 Level 10 (108,150 points)
    Currently Being Moderated
    Mar 3, 2013 8:25 PM (in response to lundman)

    You're in a better position to solve this problem than I am. You can quit Viscosity and see whether the CPU usage drops.

  • Linc Davis Level 10 Level 10 (108,150 points)
    Currently Being Moderated
    Mar 3, 2013 8:34 PM (in response to lundman)

    I have never seen the problem you describe on any of my Macs running ML. And you haven't made a report to Apple by posting here. If you feel you've found a bug, report it on the developer site. But unless you can specify a way to reproduce on a clean installation of OS X, without third-party kernel extensions, you'll be wasting your time.


More Like This

  • Retrieving data ...

Related Articles

Bookmarked By (0)


  • This solved my question - 10 points
  • This helped me - 5 points
This site contains user submitted content, comments and opinions and is for informational purposes only. Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site. All postings and use of the content on this site are subject to the Apple Support Communities Terms of Use.