Activity Monitor's pmTool shows negative numbers for messages sent/received

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Level 1

4 points

Activity Monitor's pmTool shows negative numbers for messages sent/received

About a week after restarting my Mac, Activity Monitor shows that the entries for pmTool's messages sent and received change to negative numbers. Is this normal?

1.83 GHz Core Duo, Mac OS X (10.4.11), 17" LCD

Posted on Sep 3, 2008 9:09 PM

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Answer 1

Sep 3, 2008 9:49 PM in response to Robby Cutler

This may seem like a dumb question, but: are you letting Activity Monitor run for a week? If so, it could be that the number of messages sent and received by the pmTool simply get too large over that length of time. Once numbers get too large, they "wrap around" to negative numbers.

Do the negative numbers get consistently larger? That's another sign that it's numbers that have "wrapped": when a number gets too big, it goes negative, then starts counting up to zero again. Look up "integer overflow" on the web for a more detailed explanation.

charlie

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Answer 2

Robby Cutler Author

Level 1

4 points

Sep 4, 2008 8:04 AM in response to Charles Minow

Thanks Charlie. I got the lesson on integer flow as you suggested.

Yes, I've been letting Activity Monitor run constantly in the corner of my screen. The numbers consistently got larger as you described, eventually wrapping around to the negative side and increasing from there again. I believe kernel_task or WindowServer was showing the same thing sometimes. After quitting the application and reopening it, pmTool reverted back to small positive numbers in those categories. I'll be opening Activity Monitor only when I need it now.

Appreciate your response. Robby

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Answer 3

Sep 4, 2008 6:29 PM in response to Robby Cutler

Robby Cutler wrote:
Appreciate your response. Robby

No problem.

So, just in case it's not obvious: this is mostly cosmetic, so it's not a "problem" as such, just a case where there's a limit to how big a number can get. It doesn't hurt to let Activity Monitor run for long periods of time, but just keep in mind that sometimes what it shows you might be off (or just hide the messages sent/recv'd columns, I'm not sure if what they show is all that useful anyway unless you're a programmer).

charlie

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