Note: The notion of a hot spot is relative. Hot spots depend on the filter sets that you have enabled in the filter settings. Filtered methods are opaque, in the sense that they include allocations performed in calls into other filtered methods. If you change your filter sets you're likely to get different hot spots since you are changing your point of view. Please see the help topic on hot spots and filters for a detailed discussion.
In order to prepare allocation hot spots, you have to click on the
calculate toolbar button
or choose View->Calculate Allocation Hot Spots from JProfiler's
main menu. If allocation hot spots have already been calculated, the context sensitive
menu
also gives access to this action.
Before the allocation hot spots are calculated, the allocation options dialog is shown. The class or package selection as well as the selected liveness mode are displayed at the top of the allocation call tree view.
Depending on your selection of the aggregation level, the method hot spots will change. They and their hot spot backtraces will be aggregated into classes or packages or filtered for Java EE component types.
If you click on the handle
on the left side of a hot spot, a tree of backtraces will be shown.
Every node in the backtrace tree has textual information attached to it which depends
on the allocation hot
spots view settings.
Note: This is not the number of allocations in this method.
The hot spot backtraces tree doesn't display all method calls in the JVM, it only displays
Runnable.run()
and the main method are always displayed, regardless of
the filter settings.
To quickly expand larger portions
of the hot spot backtraces tree, select a method and choose
View->Expand Multiple Levels from the main window's menu or
choose the corresponding menu item from the context menu. A dialog is shown
where you can adjust the number of levels (20 by default) and the threshold in per
mille
of the parent node's value that determines which child nodes are expanded.
If you want to
collapse an opened part of the hot spot backtraces tree, select the
topmost method that should remain visible and choose
View->Collapse All from the main window's menu or
the context menu.
DEL
key
or by choosing Hide Selected from the context menu. Percentages will be corrected accordingly as if the
hidden node did not exist.
When you hide a node, the toolbar and the context menu will get a Show Hidden
action. Invoking this action will bring up a dialog where you can select hidden elements
to be shown again.
If a node is excluded, you will get options to add a profiled package, otherwise you will get options to add a compact or ignored filter. These actions are not available for classes in the "java." packages.
By default, the difference column is sorted on the absolute values in it, this can be changed in the allocation hot spots view settings dialog.
You can remove the mark by