Too Cool for Internet Explorer

Sunday, April 4, 2004

What Is ‘kernel_task’ and Why Is It So RAM Hungry?

Every so often, I see MemoryStick reporting a lot of pageable RAM is being used. I checked out Activity Monitor and sorted by what was using the most memory. I found process 0 named kernel_task being run by root. It’s using little to no CPU at any given time, but has 36 threads and is using anywhere from 75 to 78 megabytes of real RAM and a little more than 745 megabytes of virtual RAM. The only thing I’ve been able to find by searching is old comments referencing certain HP drivers, USB ports, and OS X version 10.2.2. I don’t use any HP products, nothing is currently plugged into my USB ports, and I’m running OS X 10.3.2.

Please chime in if you know what’s going on here.

» Posted by ALBj at 09:42 PM (ET)
Category: Housekeeping, Mac


To the best of my knowledge, kernal_task is the kernel of your system (hence, process 0). It is the heart of your OS and is uber-important to the functioning of your system. Kernel extensions, like drivers to talk to printers, mice etc. are loaded wia kernel extensions. That’s why you found that old info. s Early in MacOS X’s days (!), badly behaved kernel extensions caused kernal panics (the Mac equivalent of the Blue Screen of Death). It is run as root because of it’s importance, and power - it IS your system’s heartbeat.

Any UNIX gurus should feel free to correct me here. ;)

» Posted by Ryan
April 5, 2004 11:23 PM

Ahh yes, as Mac OS catches up with Windows, you will see this more and more. OSs use the kernel tasks to run things below the GUI to ensure the tasks get top priority and are harder to screw with. The downside is that if a kernel task has a bug, it can often take out your whole system. Windows has suffered with this for years and only recently has been able to drastically reduce this problem by reorganizing the way kernel operations are handled.

The other issue with this is that kernel tasks are often unnamed more or less because they are started by the OS itself and thus get labeled with a generic “kernel task” type of label. So unless the OS provides you with a driver diagnostics (All versions of Windows do), it can be very difficult to track down which driver is causing a certain problem.

The point to this story is, you are stuck with kernel tasks, and before too many more versions, you will start seeing other similiar “generic” OS labels in your task list. I’m not certain of what is available now, but one can only hope the the Unix/Linux crowd learns from Microsoft’s mistake and provides better kernel level diagnostic tools early on.

» Posted by Queue
April 6, 2004 02:13 AM

Mac OS catching up with windows? I’d say it’s the other way round.

kernel_task uses 200mb+ of my precious ram - i’m using OS 10.3 with 768mb ram and after a reboot i only have 100mb free. the rest is being used by the OS (windowserver = 120mb, finder = 70mb etc.)

» Posted by Rob
May 18, 2004 12:34 PM

While I can certainly appreciate the responses thus far, I don’t see any real answers to the original question.

Surely there is something that can be done to relax my activity monitor and allow my Powerbook to run effectively once again?

I’m working at half the capacity I was a few weeks ago….and it really sucks!


» Posted by streamingbob
June 20, 2004 11:31 AM

for what it’s worth, ever since upgrading to OS X 10.3.4, i’ve not seen the same behavior.

» Posted by Lee Bennett
June 20, 2004 04:08 PM

I’m having a similar problem. I’m running 10.3.4 on a G4/500, 1GB RAM, IBM 60GB 7200 hard drive. I even tried a 1.5GHZ Mercury Extreme processor upgrade, but that didn’t help. After I boot, everything seems fine for a couple minutes and then the big slow down begins. I do have a USB 2.0 card installed and I use a LaCie FW DVD-RW drive, but I removed both and that didn’t help. The “kernel_task” isn’t using much real memory, but it’s hogging 90-95% of the processor. Any ideas?

» Posted by kms
July 14, 2004 01:01 PM

I seem to be having the same problem as kms on a G4 powerbook with 10.3.5. Occasionally, particularly after long wireless/ethernet connection times, kernel_task goes nuts and uses about 95% of the processor. That kind of use typically results in processor temperatures of ~145 F. Putting the machine to sleep is a fix only as long as it’s asleep, but restarting clears things up. I run one program at startup and there seems to be no correlation between number of running apps and the kernel_task problem; if anything, it seems more common with few apps running.

» Posted by Steve
August 23, 2004 05:35 AM

Well i have been experiencing similar problems, but the real issue, for me, is that this kernel task uses 3.5 Gb of Virtual memory (right after restart!) which is all that’s left on my boot drive, and eventually causes freezes.
No fix so far :-[

» Posted by dojob
September 9, 2004 07:03 AM

I am having similar Problems. I have a Quicksilver dual 1 gig with 2gig of ram and I have had the Activity monitor on my dock for weeks and today I noticed that one of the processors is always runnig at full! I have restarted, updated, everything and I can’t fix the problem! HELP!

» Posted by Ben Hosterman
September 9, 2004 02:52 PM

I think this is happening to me too. I have an iBook G4 with 648mb of RAM. The kernel task never dips below 50MB. Is this normal? The only time I really notice the slowdown is while using apps like Fireworks or Deck.
I’m not sure if the problem is the kernel task or if I just need more horsepower to run these apps. I don’t remember them being that slow until a couple of weeks ago.

» Posted by Garrett
September 12, 2004 02:42 PM

i think this started to heppen more in 10.3.5
i have a dual 2.5 with 4.5 gb of ram and currently kernel is using 1-14% of cpu, 330mb of ram and 1.3 gb of virtual ram.
i’ve been told that downgrading to 10.3.4 releases some tension on teh memory and cpu usage of teh kernel.

» Posted by Bla
October 22, 2004 03:35 AM

i have this same problem with 10.4.1. right now, kernel task is using about 900mb’s of virtual memory.

» Posted by Robert
May 29, 2005 11:44 PM

With nothing but Safari open, my kernel is using 40mb real memory, and 477mb of virtual memory. That seems a little high, that’s more than Photoshop!

» Posted by Brad Schiff
June 14, 2005 12:48 AM

I’m having the same problem under 10.4.2. Please help!

» Posted by Rob 2
July 19, 2005 04:13 PM

10.4.2 - never had the problem before. (Did a clean install of Tiger on my G4 iBook) right now its taking 41 threads, 67 megs of real memory and 735 megs of virtual memory. Have to restart a few times every day otherwise I run out of drive space!

» Posted by Justin
July 20, 2005 10:45 AM

Same problem… would someone be kind enough to email me if a solution is found?

Wes Jackson

» Posted by Wes
August 21, 2005 09:31 AM

I just upgraded to tiger, as soon as I did the same thing has happened to me, computer sooo slow, and freezes, I am hoping it wont whilst I search for help. I am using powerbook G4. Any solutions, I to have a Lacie DVD drive attached.

» Posted by tom
August 28, 2005 11:09 AM

Help on this please - I am having the same problem on a powerbook G4 12”. 47 threads, 58,46 megs real memory and 828,70 megs virtual memory being used.

» Posted by charlie Cain
September 1, 2005 04:46 PM

This problem sounds to me like there is a background process hogging both memory and processor usage. More than likely, it is a driver of some sort. I’m a little unsure as to what tools are available to do this for Mac OS, but my suggestions would be to turn off as many drivers as possible, then bring them back in one by one, rebooting between each inclusion, until you find the problem child. I know this sounds tedious and time consuming, but unless you have some really good kernel tools to tell you usage on an individual driver level, you’re probably not going to find this easily.

Another possibility that comes to mind is to check any scheduling that may be set up. It could be that the kernel is busy performing some scheduled task. This would be made more obvious if you left the computer running and it sped up some time later, possibly hours later.

» Posted by Queue
September 6, 2005 11:17 AM

I have the same problem. I just bought a new iBook G4 w/ 1.5 gig of RAM and Tiger 10.4.2.
I have noticed that when using Acquisition(p2p) the kernel task goes crazy jumping around, using 10-70% of the processor.
I have also noticed that my Airport Extreme card will just disconnect from my Linksys and a restart is the only way to connect to the internet again.
Also the kernel task will use just over a gig of virtual memory when the iBook first starts up.
A side affect of the kernel task problem is that my mouse lags heavily. To “fix” the mouse lag I turn off the Airport Card. But I use the internet a lot so this doesn’t really do anything for me except to free up the mouse lag.
I did try to turn on the Airport Card but it just won’t connect saying that there is a problem with the connection. Hope this helps guide someone in the right direction for a solution. - Mouton

» Posted by Mouton
September 18, 2005 04:49 AM

Are you guys running an HP printer or scanner on your macs? I am, and that thing has caused me no end of trouble in terms of hogging resources. The HP device seems to cause some sort of polling of the USB ports, running up the kernel_task memory requirements. Try searching for an HP Communication or some sort of HP scan activity and quitting it. The kernel_task memory might not drop down immediately, but I think you’ll notice system response is snappy once again.

» Posted by Matthew
September 23, 2005 09:01 AM

I have the same type of problem with Tiger. It is a huge resource hog. I have 1.5 G of a RAM and it is now about 75% slower than with panther. Kernel_task uses about 100 mb of RAM. Windows explorer (main part of user interface in xp) only uses about 20 MB. Good Job Mac!

» Posted by ryan
October 3, 2005 10:12 AM

i checked out and there was a thread about the very same problem.

install sidetrack for your trackpad and it should bring kernel_task down to <3%

» Posted by chris Weis
October 17, 2005 04:51 AM

Kernel_task gives me the lolly-pop all the time! Can’t use apps or put her to sleep or force quit or anything.
Here’s what I’ve got:
iBook G4 768MB 60GB OSX.3.9
Here’s what I’ve tried:
reformatting in UNIX and Mac
reinstalling (5 times)
installing updates (or not)
repairing permissions
toggling journaling
reseting PRAM
reseting power management
removing the battery

There are ZERO third-party apps on this machine. I’m running OSX only with it’s most basic components. I’ve called Apple Care and they were NO USE. What is wrong with kernel_task, Apple?

» Posted by Thomas Ryan
December 2, 2005 12:09 AM

Same issue here. When i turn off the airport it brings the kernel_task down to a very small percentage of the cpu. But turning the airport back on screws it up again, plus the connection is dead.

» Posted by jessie
December 14, 2005 08:16 PM

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