Generations

This is where the most detailed stats & info about each GC Generation is located. There are tables with total, occupied sizes by Generation, as well as cumulative STW pauses graphs, and, finally, the numerous statistical info, like Total, Min/Max, Average pause times, average interval between events and so on.

One note should be done here. Consider next table:

Generation Average Min Max
Young 1.995 GB 25.255 MB 2.197 GB
Tenured 4.691 GB 2.132 GB 7.612 GB
Heap 6.672 GB 2.420 GB 9.643 GB

Each cell contains average/min/max observed value for the given generation. So, the rule like Young+Tenured=Heap may not work here.

For example: at one point of time we observed min Young as 5mb, and in another time Tenured min was 10mb. At third time we noticed Heap min size as 15mb. At first glance, all three events were at the same time! But if -XX:+UseAdaptiveSizePolicy was enabled, all the magic ruins. When Young was just 5mb, the Tenured easily might be 1gb. So, please be accurate in your analysis and estimation.

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