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When running iotop -C 5 12 on my late-2010 Macbook Pro (10.6.7) I get repeated instances of this error:

dtrace: error on enabled probe ID 5 (ID 19507: io:mach_kernel:buf_strategy:start): illegal operation in action #3 at DIF offset 0

What's the cause of this and how do I fix it?

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2 Answers 2

up vote 6 down vote accepted

According to this blog post (with more information here), it's caused by iTunes, which DTrace "filters" so it can't be used to try to break iTunes' DRM.

Quitting iTunes resolves the error.

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I get this error even when iTunes isn't running. –  studgeek Nov 25 '12 at 14:52
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The errors are getting output to stderr, and can be filtered out by running the command as such:

sudo iotop -C 5 12 2>/dev/null

This does have the side effect of filtering out any other errors that might come up. I've found it to be an ok tradeoff, in that it's made my iotop output readable.

I'm not sure what the cause of the errors are, unfortunately. I've searched, but have not been able to find anything as of yet.

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