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Java Mission control sampling count vs. method performance

edited Sep 26, 2016 3:40PM in Java Mission Control

I ran Java mission control on my application using flight recorder. There is a column called sampling count shown across the methods that were sampled.

Can you let me know if the sample count is same as time taken for the method to execute?



  • Erik - Hotspot Engineer-Oracle
    edited Sep 26, 2016 3:40PM

    Sampling count refers to the number of times JFR stopped a thread and found that particular frame on the stack.

    The sampling algorithm may differ between JVM versions, so I don't want to go into details how it works, but the contract is that sampling count should reflect a statistical correct picture of the methods being executed by the VM. For instance, a method with a sample count of 20 should on average occur twice as often as one with sample count 10.

    The purpose of the value is to indicate how reliable the data is. A low sample count means it could be coincidence that the sampler found the method.

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