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 type of the hot spots can be selected in the combo box above the table labeled "hot spot type". The available types fall into two categories:
  1. method calls
    • method calls (show filtered classes separately)
      The displayed hot spots are calculated from method calls. Filtered classes can contribute hotspots of their own. This is the default mode.
    • method calls (add filtered classes to calling class)
      The displayed hot spots are are calculated from method calls. Calls to filtered classes are always added to the calling class. In this mode, a filtered class cannot contribute a hotspot, except if it has 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 J2EE component types.

    Note: The notion of a method hot spot is relative. Method hot spots depend on the filter sets that you have enabled on the method call recording tab of the profiling settings dialog. Filtered methods are opaque, in the sense that calls into other filtered methods are attributed to their own time. 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 hotspots and filters for a detailed discussion.

  2. J2EE related calls
    • JDBC calls
      The displayed hot spots are JDBC calls. JDBC call recording has to be enabled in the profiling settings.
    • JMS calls
      The displayed hot spots are JMS calls. JMS call recording has to be enabled in the profiling settings.
    • JNDI calls
      The displayed hot spots are JNDI calls. JNDI call recording has to be enabled in the profiling settings.
    • URL invocations
      The displayed hot spots are URL invocations. URL call tree splitting has to be enabled in the profiling settings. URL splitting can be customized in the profiling settings or by registering a custom handler with the profiling API. In the profiling settings you can also specify if all URLs or only URLs which lead to the invocation of an unfiltered class (the default setting) should be displayed.

    Depending on your selection of the aggregation level, the hot spot backtraces can be aggregated into classes or packages. The J2EE-related hot spots themselves do not change for different aggregation levels.

    For the J2EE related hot spot types, please see the help on the Java subsystems tab of the profiling settings for more information on how these calls are recorded.

  Every hot spot is described in several columns:
  • If a J2EE-related hot spot type is selected, the recorded data for the call is displayed. For method call hot spots types, 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.
    • J2EE components
      the display name of the J2EE component.
  • the inherent 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 inherent 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.

The hot spot list can be sorted on all columns.

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 hot spot 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 percentage 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.
    • J2EE components
      the display name of the J2EE 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 J2EE components and displays the relevant nodes in the hot spot backtraces tree with special icons that depend on the J2EE component type:

 servlets
 JSPs
 EJBs

For JSPs and EJBs, JProfiler shows a display name:
  • JSPs
    the path of the JSP source file
  • EJBs
    the name of the EJB interface

If URL splitting is enabled, each request URL creates a new node with a  special icon and the prefix URL:, followed by the part of the request URL on which the hot spot backtraces tree was split. Note that URL nodes group request by the displayed URL.

You can disable both J2EE component detection as well as URL splitting on the Java Subsystems tab of the profiling settings. Also, the URL splitting method can be customized in the profiling settings or with a custom handler in the profiling API.

  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 J2EE 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. J2EE 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.
  • J2EE components
    Every node in the tree is a J2EE 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

  • unfiltered classes
    Classes which are unfiltered according to your configured filter sets are used for the construction of the hot spot backtraces tree.
  • first level calls into unfiltered classes
    Every call into a filtered class that originates from an unfiltered class is used for the construction of the hot spot backtraces tree. Further calls into filtered 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 10 levels from the main window's menu or choose the corresponding menu item from the context menu. 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.
  You can stop and restart CPU data acquisition to clear the hot spots view and freeze all views to ensure that the hot spots view remains static.