Hot Spots View

The hot spots view shows a list of calls of a selected type. The list is truncated at the point where calls use less than 0.1% of the total time of all calls. See the help on the estimated CPU time/elapsed time setting and take into account the selection of the thread state selector to properly assess the meaning of these time measurements. By opening a hot spot node, the tree of backtraces leading to that node are calculated and shown.
  The hot spot calculation options can be selected in the drop-down list above the table labeled "Hot spot options". The times calculation section lets you calculate hot spots from
  • Self
    This is the default option and is preferable in most situations. Hot spots are calculated based on their cumulated self times, excluding calls to other recorded methods.
  • Total
    With this option, hot spots will be calculated based on the total times that you see in the call tree. Methods near the top of the call stack will always be the top hot spots.
Hot spots can be different, depending on how unprofiled classes are handled:
  • Show separately
    The displayed hot spots are calculated from all method calls in the call tree. Unprofiled classes are measured if they are called directly from profiled classes, so they can contribute hot spots of their own. This is the default mode.
  • Add to calling class
    Calls to unprofiled classes are always added to the calling class. In this mode, an unprofiled class cannot contribute a hot spot, except if it is a thread entry method (run and main methods).
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.

By setting a view filter, you can analyze hot spots in selected packages. The cutoff will then be calculated relative to the set of filtered classes. In that way, hot spots may be shown that are otherwise below the cutoff threshold.

Note: The notion of a method hot spot is relative. Method hot spots depend on the filter sets that you have enabled in the filter settings. Filtered methods are opaque, in the sense that calls into other filtered methods are attributed to their own times. If you change your filter sets you're likely to get different method hot spots since you are changing your point of view. Please see the help topic on hot spots and filters for a detailed discussion.

  Every hot spot is described in several columns:
  • The hot spot column shows a name which depends on the aggregation level:
    • methods
      a method name that is either fully qualified or relative with respect to to the calling method.
    • classes
      a class name.
    • packages
      a package name.
    • Java EE components
      the display name of the Java EE component.
  • the self time, i.e. how much time has been spent in the hot spot together with a bar whose length is proportional to this value. All calls into this method are summed up regardless of the particular call sequence.

    If the method belongs to an unfiltered class, this time does not include calls into other methods. If the method belongs to a filtered class, this time includes calls into other filtered methods.

  • the average time, i.e. the self time (see above) divided by the invocation count (see below).
  • the invocation count of the hot spot. If "Sampling" is selected as the method call recording type, the invocation count is not available.
  If you click on the  handle on the left side of a hot spot, a tree of backtraces will be shown. Every entry in the backtrace tree has textual information attached to it which depends on the view settings.
  • a percentage number which is calculated with respect either to the total time or the called method.
  • a time measurement in ms or µs of how much time has been contributed to the parent hot spot on this path. If enabled in the view settings, every node in the hot spot backtraces tree has a size bar whose length is proportional to this number.
  • an invocation count which shows how often the hot spot has been invoked on this path.

    Note: This is not the number of invocations of this method.

  • a name which depends on the aggregation level:
    • methods
      a method name that is either fully qualified or relative with respect to to the calling method.
    • classes
      a class name.
    • packages
      a package name.
    • Java EE components
      the display name of the Java EE component.
  • a line number which is only displayed if
    • the aggregation level is set to "methods"
    • line number resolution has been enabled in the profiling settings
    • the calling class is unfiltered

    Note that the line number shows the line number of the invocation and not of the method itself.

  JProfiler automatically detects Java EE components and displays the relevant nodes in the hot spot backtraces tree with special icons that depend on the Java EE component type:

 servlets
 JSPs
 EJBs

For certain classes, JProfiler shows a display name:
  • JSPs
    the path of the JSP source file
  • EJBs
    the name of the EJB interface
  • RMI proxies
    the name of the remote interface
  • Web service proxies
    the QName of the end point
If HTTP splitting is enabled in the servlet probe each request URL creates a new node with a  special icon and the prefix HTTP:, followed by the part of the request URL on which the hot spot backtraces tree was split. Note that HTTP nodes group request by the displayed URL.
  The hot spots view has an aggregation level selector. It allows you to switch between
  • methods
    Every node in the tree is a method call. This is the default aggregation level. Special Java EE component methods have their own icon (see above) and display name, the real class name is appended in square brackets.
  • classes
    Every node in the tree is a single class. Java EE component classes have their own icon (see above) and display name, the real class name is appended in square brackets.
  • packages
    Every node in the tree is a single package. Sub-packages are not included.
  • Java EE components
    Every node in the tree is a Java EE component. If the component has a separate display name, the real class names are omitted.
When you switch between two aggregation levels, JProfiler will make the best effort to preserve your current selection. When switching to a a more detailed aggregation level, there may not be a unique mapping and the first hit in the hot spot backtraces tree is chosen.

The hot spot backtraces tree doesn't display all method calls in the JVM, it only displays

  • profiled classes
    Classes which are profiled according to your configured filter sets are used for the construction of the hot spot backtraces tree.
  • first level calls into unprofiled classes
    Every call into a filtered class that originates from a profiled class is used for the construction of the hot spot backtraces tree. Further calls into unprofiled classes are not resolved. This means that a filtered node can include information from other filtered calls. Filtered nodes are painted with a red marker in the top left corner.
  • thread entry methods
    The methods Runnable.run() and the main method are always displayed, regardless of the filter settings.

  When navigating through the hot spot backtraces tree by opening method calls, JProfiler automatically expands methods which are only called by one other method themselves.

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.

  If a method node is selected, the context menu allows you to quickly add a method trigger for the selected method with the  add method trigger action. A dialog will be displayed where you can choose whether to add the method interception to an existing method trigger or whether to create a new method trigger.
  Nodes in the hot spot backtraces tree can be hidden by selecting them and hitting the 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.

  For method, class or package nodes, the context menu and the View menu have an Add Filter From Selection entry. The sub-menu contains actions to add appropriate filters as well as an action to add an ignored method entry.

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.

  You can stop and restart CPU data acquisition to clear the hot spots view.