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Question by gil g. · Mar 14, 2013 at 04:13 PM ·

Wait functions listed high in CPU sampling

Hi,

I was having troubles explaining to a customer why in CPU sampling he saw the wait methods as the highest CPU execution time. Can you assist in providing a clear explanation ?

Thanks,

Gil.

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Answer by Michael K. · Mar 26, 2013 at 09:23 AM

Actually it does, but that is not the point.

CPU sampling does not only sample how much CPU is consumed, it samples what threads do with the CPU. When a thread waits for a long time, thus does not really use the CPU (again not completely true anyhow) than we also see this and mark it accordingly. In the same way we see Sync or GC time, because we know that the thread is syncing or blocked by GC during that time.

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Answer by Rick B. · Mar 14, 2013 at 05:48 PM

You should be able to get context of that wait method in the CPU Sample (i.e. what called it, such as an LDAP authentication or DB socketRead0 request), otherwise you can just open the Methods Hotspots dashlet and search for the wait method to see the context in which it is called.

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avatar image gil g. · Mar 14, 2013 at 05:54 PM 0
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this is all understood. the question the user raised is that "wait" does not consume cpu.

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