CLion 2021.2 Help

Advanced configuration

Besides the standard options available, CLion enables you to perform low-level configuration of the underlying platform and the Java runtime.

JVM options

CLion runs on the Java Virtual Machine (JVM), which has various options that control its performance. The default options used to run CLion are specified in the following file:

<IDE_HOME>\bin\clion64.exe.vmoptions
CLion.app/Contents/bin/clion.vmoptions
<IDE_HOME>/bin/clion64.vmoptions

Configure JVM options

Do one of the following to create a copy of the default file with JVM options in the configuration directory that will override the original file:

  • From the main menu, select Help | Edit Custom VM Options.

  • If you do not have any project open, on the Welcome screen, click Configure and then Edit Custom VM Options.

  • If you cannot start CLion, manually copy the default file with JVM options to the CLion configuration directory.

If you do not have write access to the CLion configuration directory, you can add the CLION_VM_OPTIONS (CLION64_VM_OPTIONS on Windows) environment variable to specify the location of the file with your preferred JVM options. This file will override both the original default file and the copy located in the CLion configuration directory.

Common options

The default values of the JVM options should be optimal in most cases. The following are the most commonly modified ones:

OptionDescription
-Xmx

Limits the maximum memory heap size that the JVM can allocate for running CLion. The default value depends on the platform. If you are experiencing slowdowns, you may want to increase this value, for example, to set the value to 2048 megabytes, change this option to -Xmx2048m.

For more information, see Increase the memory heap of the IDE.

-XmsSpecifies the initial memory allocated by the JVM for running CLion. The default value depends on the platform. It is usually set to about half of the maximum allowed memory (-Xmx), for example, -Xms1024m.
-XX:NewRatioSpecifies the ratio between the size of the young and old generation of the heap. In most cases, a ratio between 2 and 4 is recommended. This will set the size of the young generation to be 1/2 to 1/4 of the old generation correspondingly, which is good when you are often working on one project and only a few files at a time. However, if you are constantly opening new files and switching between several projects, you may need to increase the young generation. In this case, try setting -XX:NewRatio=1, which will make the young generation as large as the old generation, allowing objects to remain in the young generation for longer.

For more information about the available JVM options, see the java reference for Windows or macOS/Linux.

Platform properties

CLion enables you to customize various platform-specific properties, such as the path to user-installed plugins and the maximum supported file size. The default properties used to run CLion are specified in the following file:

<IDE_HOME>\bin\idea.properties

CLion.app/Contents/bin/idea.properties

<IDE_HOME>/bin/idea.properties

Configure platform properties:

Do one of the following to create an empty idea.properties file in the configuration directory that will override the values from the original file:

  • From the main menu, select Help | Edit Custom Properties.

  • If you do not have any project open, on the Welcome screen, click Configure and then select Edit Custom Properties.

  • If you cannot start CLion, manually create an empty idea.properties file in the CLion configuration directory.

If you do not have write access to the CLion configuration directory, you can add the CLION_PROPERTIES environment variable to specify the location of the idea.properties file. The properties in this file will override the corresponding properties in both the original default file and the one located in the CLion configuration directory.

Common properties

Users often change the location of the default IDE directories. For more information, see Change the location of IDE directories.

Limits that can affect performance:

PropertyDescription
idea.max.content.load.filesizeMaximum size of files (in kilobytes) that CLion is able to open. Working with large files can affect editor performance and increase memory consumption. The default value is 20000.
idea.max.intellisense.filesizeMaximum size of files (in kilobytes) for which CLion provides coding assistance. Coding assistance for large files can affect editor performance and increase memory consumption. The default value is 2500.
idea.cycle.bufferMaximum size of the console cyclic buffer (in kilobytes). If the console output size exceeds this value, the oldest lines are deleted. To disable the cyclic buffer, set idea.cycle.buffer.size=disabled.
idea.max.vcs.loaded.size.kbMaximum size (in kilobytes) that CLion loads for showing past file contents when comparing changes. The default value is 20480.

CLion provides a number of other properties that define interaction with the environment (window managers, launchers, the file system, and so on). Most of them act like hidden settings (in the sense that they are not evidently exposed), which you may need to enable or disable in certain cases. Change these properties only if advised by JetBrains Support.

Adjusting CPU Cores Number

You can adjust the number of CPU cores to be used by the IDE when running the active tasks (e.g indexing header files, updating symbols, and so on) in order to keep the performance properly balanced between CLion and other applications running on your machine.

To set up the number of CPU cores:

  1. Press Ctrl+Shift+A or choose Help | Find Action from the main menu. In the popup that opens, start typing Registry, select the corresponding item and press Enter.

    Searching for Registry in Find Action
  2. In this dialog, start typing cidr.indexer.thread.count. The IDE highlights the corresponding key.

    Registry dialog

    Click the Value field of the highlighted string and enter the desired number of CPU cores assuming the following:

    • Negative value N means that the actual number of CPU cores will be reduced by N to determine how many cores will be used. For example, for 8 cores CPU the value -1 means, that 7 cores shall be used.

    • Zero value means that every available core shall be used.

    • Positive value determines the cores number to be used directly.

Last modified: 08 October 2021