GoLand
 
2023.2
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  1. Profiling for tests
  2. Read the profiler snapshot

Read the profiler snapshot

Last modified: 23 August 2023

In the Profiler tool window, the collected data is presented on several tabs: Flame Graph, Call Tree, and Method List.

Navigate the snapshot

You can jump between the tabs while staying focused on a specific method. Right-click the necessary method and select another view in which you want to open it.

https://resources.jetbrains.com/help/img/idea/2023.2/go_navigate_profiler.png
Gif

For a method on any tab, you can open the Merged Callees and Back Traces trees. Right-click the method and select Method Merged Callees or Method Back Traces respectively.

Flame Graph

The flame graph visualizes the application call tree with the rectangles that stand for frames of the call stack, ordered by width. Frames that consume more resources are wider than the others and are placed on the left.

Frame type

Light theme

Dark theme

Project code

Yellow

Yellow

Library code

Purple

Grey

Native code

Blue

Blue

Block details shown in the flame graph

Get call details

  • Hover over a block to see the tooltip with frame details. The tooltip shows the share of time in the entire snapshot and in the frame's direct parent.

Zoom the graph

  • Use the the Zoom in button and the Zoom out button buttons on the flame graph's toolbar or the scroll wheel to zoom the graph.

  • To focus on a specific method, double-click the corresponding block on the graph.

  • To restore the original size of the graph, click 1:1 on the toolbar.

  • If you want to locate a specific method on the graph, start typing its name or click Show Search Toolbar and type the name in the search bar.

    The graph highlights all blocks with method names matching your search request.

    Use Previous Occurrence and Next Occurrence for fast navigation between search results. Using the buttons on the toolbar, you can also search either the whole graph or a specific subtree and navigate to the results as soon as something was found.

Using the search in the Flame Graph tab

Capture the graph

You can capture and export the graph separately from other data in the snapshot.

  • Click Capture Image and select Copy to Clipboard or click Save to export the graph as an image in the .png format.

tip

For more information about flame graphs, see Flame Graphs.

You can visualize the difference between two snapshots on the flame graph.

Compare with a baseline

  1. Open two snapshots. To open snapshots, you can run the profiler twice or go to Run | Open Profiler Snapshot and select snapshots here.

  2. Click the Compare With Baseline button and select the snapshot that you want to compare against.

    A separate diff tab will open with the results of the comparison, combining two flame graphs and showing the differences as red and green.

    If you see that some part of the frame is green, it means that the corresponding method became faster during this profiler run. The red color means that the corresponding method became slower.

    https://resources.jetbrains.com/help/img/idea/2023.2/go_compare_with_a_baseline.png
    Gif

Call Tree

The Call Tree tab organizes the sampled data in a tree-like structure.

call tree tab in the profiler results

For each method, the tab shows the following information:

  • Share in the total execution time or parent's execution time

  • The aggregated execution time

  • Recursive calls

By default, the percentage is relative to the total execution time. You can choose to view the numbers relative to the parent frame.

Switch the percentage between total and parent

  • Click the Presentation Settings button and select Show Percent of Total Time or Show Percent of Parent.

Collapse recursive calls

A stack that involves recursion may be very difficult to analyze. In a regular Call Tree view, recursive calls are displayed as they are called – one after another, which may lead to almost infinite stack scrolling.

GoLand detects recursion when the same method is called higher up in the call stack. In this case, the subtree is taken out of the call tree and then attached back to the first invocation of that method. This way you can bypass recursion and focus on methods that consume most of the resources and calls that they make.

Collapsing recursive calls allows you to see the total amount of time spent in these calls as if there was no recursion.

Collapse recursive calls button

Folded recursive calls are marked with the the Recursion icon icon on the Call Tree tab. Click it to open the recursive call tree in a separate tab. You can preview the number of merged calls in the tooltip that appears on hovering over the recursion icon.

Unfolding a collapsed recursion

What-if: focus on specific methods

GoLand allows you to examine specific nodes and subtrees in the Call Tree: you can exclude particular methods or other way round, focus only on the nodes in which you are interested at the moment.

Right-click the necessary node on the Call Tree tab and select one of the following options to open the results in a dedicated tab:

  • Focus On Subtree: show only the selected method call. Parent method sample counter shows only the time spent in the selected subtree.

  • Focus On Call: show the selected method and the methods that call it. When this option is enabled, every frame shows only the time spent in the selected method.

  • Exclude Subtree: ignore the selected method call.

  • Exclude Call: ignore all calls to the selected method.

Using the What-if feature

Method List

The Method List collects all methods in the profile data and sorts them by cumulative sample time. Every item in this list has several views:

  • Back Traces shows the hierarchy of callers. Use this view to trace which methods call the selected method.

  • Merged Callees is the call tree summarizing the methods down the call hierarchy.

  • Callee List is the method list summarizing the methods down the call hierarchy.

method list tab in the profiler results