The objects comparison is one of the memory comparisons. It is created by
invoking the memory comparison wizard. For more information on
snapshot comparisons, please see the snapshot comparison overview.
The wizard has the following additional steps:
Select snapshots
The objects comparison compares two snapshot files. In this step, you select the first
and the second snapshot file for the comparison. The combo boxes contain all snapshot
files that have been added
to the snapshot selector. The first and second snapshot files must be
different.
Recording type
In this step, you choose whether you want to compare
All objects All objects on the heap will be compared.
Recorded objects
Only objects that were recorded will be compared when this option
is selected.
Heap snapshot objects
All objects that were captured in a heap snapshot taken in the heap walker
will be compared when this option is selected. Heap snapshot must be present in both
selected snapshots
to yield meaningful results. This is the only option that works for HPROF heap dumps.
View parameters
In this steps you can select aggregation and liveness mode (only for recorded objects),
just as for the
all objects view and the
recorded objects view.
Each row in the objects comparison has the following columns:
the name of the class
the size in the second
snapshot file minus the size in the first snapshot file
the instances in the second
snapshot file minus the instances in the first snapshot file
The second column incorporates a bidirectional bar chart. Increases are painted in
red and to the right, while
decreases are painted in green and to the left. In the view
settings dialog you can choose whether you want this bar chart to display absolute changes or
the percentage of the change. The other value is displayed in parentheses. This setting
also
determines how this column is sorted.
The second column can show either size or instances.
This is configurable in the view settings dialog
and is called the primary measure.
By default, only classs that have changed from one snapshot file to the other
are displayed. You can change this behavior in the view
settings dialog.
At the bottom of the objects comparison is a view filter selector
that filters data for specific package or class names.
Please note that if the current comparison compares "All objects" (see above), the
numbers will likely not correspond
with the object comparison since the allocation comparisons only compare recorded
objects.
At the bottom of the objects comparison is a view filter selector
that filters data for specific package or class names.