kernel task

[rstilley]

I have a problem with my install of OS X. I installed it on my Lombard Powerbook, and about five months ago the backside cache failed on my card.

After this happened I re-installed OS X several times, and if I do something intensive with the system, like copy a large file from the server, the system will slow down. If I type top -u in the Terminal, a process named kernel_tas(k) (PID 0) has taken over the system, and is grabbing over 50% of the CPU cycles. The only way I can get it to stop is to restart.

I attributed it to the cache problem, but today I received my PowerLogix G4 upgrade for this Powerbook. The speed is great, and it works normally, but the kernel task problem still appears. I really thought it would go away. Also, I have not seen this problem on a couple of G4 towers that have OS X installed on them.

Does anyone have any idea what could be causing this? Also, should I re-install OS X? Does the system get built specifically for a particular CPU? Would my system work better with the new G4 if it were re-installed?

Thanks for any help you can give me.

Regards,

--R

[Craig R. Arko]

Quote: Originally posted by rstilley If I type top -u in the Terminal, a process named kernel_tas(k) (PID 0) has taken over the system, and is grabbing over 50% of the CPU cycles. The only way I can get it to stop is to restart. Does anyone have any idea what could be causing this? Also, should I re-install OS X? Does the system get built specifically for a particular CPU? Would my system work better with the new G4 if it were re-installed? Thanks for any help you can give me. Regards, --R

1) Built for a specific CPU: I don't think so. OS X loads the hardware support dynamically, so it should just deal with the hardware it detects at bootup. Some of the accelerator boards do require a kernel extension (.kext) file to function fully.

2) kernel_task: This does seem to run rampant sometimes. I think this is the process scheduler (can anyone confirm this?) and it seems to be getting into a race condition of some kind. This may well be a Darwin bug.

[rstilley]

Thanks. It is very annoying. I spoke with Apple Tech Support after it first reared it's head and they didn't seem to know anything about it.

I hope to get more replies and more information.

Thanks.

[xchanyazy]

You can try renicing the kernel task

sudo renice 20 0

I've never had my kernel task take up that much processing power before though, so I'm not sure how that would affect your system. If it doesn't do anything, you can always set it back to it's default by:

sudo renice 0 0

You might want to check out the man page for renice if you're wondering what it does.

[rstilley]

Thanks for the tip. Unfortunately, it didn't help. The process just kept on chuggin' taking over 50% of the CPU. It has remained active long enough to make the fan in the Powerbook come on, something that very rarely ever happened.

The puzzling this is: I expect the kernel to get very active when heavy processing is going on, but then after that, it stays at the high level, even when the computer is just sitting there. I can quit all applications except Terminal (So I can watch the process) and it's still up there. It will not get released until I restart.

I haven't heard of anyone else with this problem, so I have to wonder what it is about my system that makes it peculiar to me.

Thanks for the help. (Still looking for more replies!)

--R

[griffman]

Do you use the Palm Desktop beta? There's a thread on the Apple Discussions board in this path about the problem you're having:

Discussions > Mac OS X > Mac OS X (10.1) > Using Technologies > Unix > kernel_task taking 90% CPU

It seems that it might be related to the Palm Desktop beta app...

-rob.

[mervTormel]

first, the kernel task is, indeed the scheduler. and it's the swapper.

if it is taking more than 10% of your cycles, there is something very wrong. adequate memory?

second, DO NOT renice the kernel task ! that way lies madness.

it is generally considered bad form to modify scheduling priorities of system tasks.

[rstilley]

OK - here's the deal. After talking with PowerLogix, I decided to re-install OS X from scratch.

I dumped everything off the drive and when I would get a new version of OS X on the drive, I would try something to trigger the kernel task, like copying large files from the network. All the way through OS X 10.0.4, sometimes the kernel task would pop up to the top of the window, but would eventually subside.

I finally got to the point where I needed to upgrade to OS 9.2.1 so I could upgrade to OS X 10.1.

Now, immediately after that upgrade, with nothing else done, the problem is back. Once started, the kernel task hangs on like an attack dog.

I will probably try calling Apple, but I doubt they will talk to me about it since I am using an upgrade processor.

If you guys have any more suggestions, please let me know. And thanks for all the help!!

BTW, I'm not using the Palm software. This started last fall before it came out.

--R

[Auricchio]

I also get the kernel task hog problem now and then on a 101/bronze powerbook. It seems to happen after a couple dozen sleep/wakeup cycles, but that might not be the cause. When I recognize the slowdown (and verify it with top), then I can reboot. If I wait too long, the system gets so bad I just give up and reset.

Also, after a couple dozen sleep/wakeups, I'll sometimes get a sleep failure. I close the lid. Screen goes black, backlight stays on, disk spins for about 20 seconds. Then nothing, except the caps lock light works. No flashing sleep light. I have to reset.

These problems used to happen on 10.0.4 too, and still on 10.1.2.

My system is a 333MHz/320MB one.

[dseelyjr]

Interesting. I've had the same problem, also on a Lombard (Bronze) PowerBook. I finally "cured" it by reducing the number of applications launched automatically at start-up (controlled by the login pref). I continue checking top -u to be sure, but haven't seen any recurrence of the problem. Don't know why it happens, don't know why it stopped ...

Dan

[rstilley]

Thanks! I currently have four apps launching; I'll turn them all off and see if it works and let ya'll know.

Regards,

--R

[Auricchio]

Aha. I have stickies, terminal, and system prefs automatically launch.

I used to also have Classic start on login, but an Apple TIL article said to disable that to prevent copy/paste problems between X and Classic apps. So now I'm down to three automatic-launching apps.

I'll see if the sleep problem happens again.

[rstilley]

The startup of Applications at Login may have been the culprit. In the first chance I have had to try out this theory, I disabled all apps at startup. I then started Terminal and started top -u so I could watch. The I started copying a 240 MB file from the server, and then started IE at the same time. The kernel task popped up to the top of the list for a few seconds a couple of times, but always released, and then went back to normal after the file copy was over.

I'm going to test this over the next few days to see if this indeed fixes the problem.

I'm also curious to see if this fixes my sleep problem as well (one problem at a time!)

Thanks for the help - I'll post a followup.

--Ricky

[rstilley]

After a couple of days running without launching apps at startup, I have had only one instance where the kernel task ran rampant, and that was after I launched a couple of programs at once while doing something else that was cpu-intensive.

Looks like this is the solution.

Thanks to everyone.

--R