After running flawlessly for 2 years, my 6 Gig Mac Pro has started to suffer a kernel panic about once a day. Nothing really has changed as far as I know. Two details, probably irrelevant, I installed Lion about a month+ ago. And I have had an Android tablet attached via USB and enabled for remote debugging.

I ran a memory diagnostic (rember) and it didn't find any problems.

This is what I find in the Kernel log just before the crash:

Sep 22 15:27:59 monster kernel[0]: (default pager): [KERNEL]: ps_select_segment - send HI_WAT_ALERT
Sep 22 15:28:00 monster kernel[0]: macx_swapon SUCCESS
Sep 22 15:28:32 monster kernel[0]: (default pager): [KERNEL]: ps_select_segment - send HI_WAT_ALERT
Sep 22 15:28:34 monster kernel[0]: macx_swapon SUCCESS

I've seen a variety of messages mentioning these errors but nothing conclusive.

If there's a hardware problem, is there a definitive diagnostic that I can run to prove or disprove it?

Any tips or troubleshooting guide will be appreciated! Thanks,


  • Please provide a more accurate account of your system: what model of Mac Pro do you have (About This Mac > System Report > Model Identifier), do you have any VM software or any additional 3rd party drivers installed, what are you doing when it panics, etc.?
    – user10355
    Commented Sep 23, 2011 at 5:00
  • Mac Pro "early 2009". I had VMWare installed but not running. Since then I have updated to VMWare FUsion 4 which should be Lion compatible. Also, and I think importantly I recently have been debugging Android apps, controlling an android device over a USB cable, debugging and so on. Other advice I have gotten seems to point as that as a possible smoking gun...
    – pitosalas
    Commented Sep 23, 2011 at 15:37
  • @pitosalas , from the given information in the situation you describe, I think you probably answered your own question there. Incompatible hardware or hardware that loses it's physical connection slightly has always had the potential to crash a mac, all the way from Mac OS (Classic) 7.5 to current Mac OS X.LargeCatHere, and may well into the future including 10.9, unless they are actively improving the software to eliminate such hangups. As far as what's possible: a little system file that has been corrupted (reinstall OS to fix) to your motherboard being damaged. Basically the whole range. Commented Jul 25, 2013 at 20:31

4 Answers 4


In my mind there are a couple of likely issues. If the machine is crashing with a kernel panic I would suspect the hard drive is on it's way out. If the machine is simply restarting without warning then I would suspect the memory.

To see if it is the memory it might be as simple as removing each stick of ram and blowing any dust off with compressed air and putting it back in. If this doesn't resolve it, I would get a new drive and clone the system using a tool like Carbon Copy Cloner or SuperDuper! Boot from the new drive and see if the issues go away.

If neither work then you could try reinstalling OS X, I doubt that's the issue. You more than likely have a failing video card or logic board if the above suggestions don't work.

  • Thanks for the excellent response!... To be specific, the crash is the mac equivalent of the blue screen of death: grey curtain and then multi lingual "you;re hosed" message. Press and hold power button is the only way to get it to reboot at that point. That's 'simply restarting without warning' right? So probably according to you that would be a disk problem, right? Can I test the disk somehow? Thanks again!
    – pitosalas
    Commented Sep 22, 2011 at 21:11
  • I agree with Dustin. Either it's a hard drive or it's the ram. Remember that a Mac pro has a specific way of installing memory sticks, if you decide to test the ram theory (which would be my first try). Usually, ram sticks have lifetime warranties, thus this story should see a happy ending. :-)
    – Fred
    Commented Sep 22, 2011 at 21:14
  • It's called a Kernel Panic and it's not the same thing as a sudden shutdown. Sudden shutdowns typically occur when the CPU surpasses safe operating temps (100-105 C) and to protect your computer, the system shutdowns. A KP results when the the kernel itself crashes. Kernel's are to be thought of as intermediates between the hardware and the software. They are the fundamental component of the OS (hence "kernel"). They also do not tolerate faults of any kind. If one is found, they crash. We need your logs (see support.apple.com/kb/ht2546). Other reading: support.apple.com/kb/TS3742
    – user10355
    Commented Sep 23, 2011 at 4:55
  • Additionally, I wouldn't jump the gun on faulty hardware just yet and rush out to replace your HDD. Do some more testing. It could be as simple as a software conflict.
    – user10355
    Commented Sep 23, 2011 at 4:56

The entries in logs means that your OSX is out of physical memory and it started to use swap space. This could cause by some specific process (such as Apache, PHP, etc.). Make sure that you enough swap space (top) and you'll find the right process which causing that issue.

What you can do:

  • monitor for changes in Activity Monitor (sorted by memory usage or CPU)
  • check your Console app for crash logs and backtraces with more specific information which you can Google it (e.g. buggy kernel modules)
  • monitor your dmesg and system.log file (sudo tail -f /var/log/system.log) for more errors before the crash
  • monitor for new processes via sudo newproc.d
  • Run Mac in recovery mode (keep holding ⌘ cmd + R on startup), then try to Repair Disk and Repair Disk Permissions using Disk Utility.
  • check for kernel modules which can be buggy, see: How to unload kernel modules
  • if you've Magic SysRq key on your Mac, try to use it when system goes freeze
  • test your RAM (e.g. using Rember app)
  • test your OSX for common system issues (e.g. using OnyX app)
  • monitor temperature of your CPU, there are few apps (if this is the case, buy a cooling pad)

Please see the similar issue:

Mountain Lion Screen Freeze


It turned out to be bad memory. I removed and replaced the memory as suggested above (and increased my total memory in the process because new ram is so cheap) and my machine has been working with no problems since. Thanks all!


Overheating? How long since you vacuumed out the dust from in there? It tends to accumulate inside my Mac Pro.

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