Profiler results are confusing

Question

Here is a picture of CPU monitoring provided by VisualVm profiler. I'm confused because I can't understand what does percentage means?As you can see for CPU the number is 24,1 of what?overall cpu time?and gc - 21,8 the same question.What is 100% in both cases?Please clarify this data.

Answer 1

CPU usage is the total CPU usage of your system. The GC activity shows how much of the CPU is spent by the GC threads.

In your example, it looks like the GC was executing and thus contributing to the majority of the total CPU usage in the system. After the GC finished, there was no CPU used.

You should check if this observation is consistent with your GC logs, the logs will shows you the activity around the 19:50 time.