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Don't understand CPU view :(

Moderators: Vladimir Kondratyev, Anton Katilin

Don't understand CPU view :(

Postby Gibson » Wed Apr 20, 2005 2:05 pm

A few questions:
1) What is the difference between "wall time" and just "time"?
2) Why do I only see "time" in snapshots generated by sampling?
3) Why are the "own time" views always empty?
4) Is it normal that the "noticeable" slowdown during tracing means that my application runs approximately 100x slower?

R

(YK 4.0.8, integrated with Idea Irida build 3290)
Gibson
 
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Postby Vladimir Kondratyev » Thu Apr 28, 2005 3:03 pm

1) What is the difference between "wall time" and just "time"?


"wall time" is a time that was spent in a method including time when the thread wasn't running.

2) Why do I only see "time" in snapshots generated by sampling?


This is limitation of sampling method. Instead of tracing, sampling just periodically scans thread call stacks. So sampler doesn't know what methods were invoked in the period between scans.

3) Why are the "own time" views always empty?


Actually it's a bug (or not implemented feature :)). The reason is that all "own times" are less than 1% of total thread time, i.e. there is nothing to show.


4) Is it normal that the "noticeable" slowdown during tracing means that my application runs approximately 100x slower?


It's possible. I'm not sure about 100x, but real value depends on code structure. Profiler agent listens all method enter/exit events, so if you application calls zillions of methods, then everything will be slow.

Regards,
Vladimir
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