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Figure 3-10. Java Flight Recorder Memory panel
The graph here shows that memory is fluctuating fairly regularly as the young generation is
cleared (and interestingly enough, there is no overall growth of the heap in this application:
nothing is promoted to the old generation). The lower-left panel shows all the collections that
occurred during the recording, including their duration and what kind of collection they were
(always a ParallelScavenge in this example). When one of those events is selected, the
bottom-right panel breaks that down even further, showing all the specific phases of that col-
lection and how long each took.
As can be seen from the various tabs on this page, there is a wealth of other available inform-
ation: how long and how many reference objects were cleared, whether there are promotion
or evacuation failures from the concurrent collectors, the configuration of the GC algorithm
itself (including the sizes of the generations and the survivor space configurations), and even
information on the specific kinds of objects that were allocated. As you read through
Chapters 5 and 6 , keep in mind how this tool can diagnose the problems that are discussed
there. If you need to understand why CMS bailed out and performed a full GC (was it due to
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