December 2nd, 2005

Psychic debugging: Why your CPU usage is hovering at 50%

Raymond Chen
Raymond Chen

Sometimes psychic debugging consists merely of seeing the bigger picture.

On one of our internal bug-reporting mailing lists, someone asked, “How come when I do XYZ, my CPU usage goes to 50%?”

My psychic answer: “Because you have two processors.”

The response was genuine surprise and amazement. How did I know they had two processors? Simple: If they had only one processor, the CPU usage would be 100%. This seems unhelpful on its face, but it actually does help diagnose the problem, because now they can search the bug database for bugs in the XYZ feature tagged “100% CPU” to see if any of those apply to their situation. (And in this case, it turns out that one did.)

Category
Old New Thing
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Author

Raymond Chen

Raymond has been involved in the evolution of Windows for more than 30 years. In 2003, he began a Web site known as The Old New Thing which has grown in popularity far beyond his wildest imagination, a development which still gives him the heebie-jeebies. The Web site spawned a book, coincidentally also titled The Old New Thing (Addison Wesley 2007). He occasionally appears on the Windows Dev Docs Twitter account to tell stories which convey no useful information.

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