Performance tuning tips

On-the-fly code analysis is one of the most performance-consuming processes in CLion. To lighten it up, you can configure the highlighting level for the currently opened file: none, syntax, or all problems. Use the inspection widget in the upper-right corner of the editor:

As an alternative to configuring individual checks or files one by one, try Power Save Mode. It disables all inspections and other highly-consuming background tasks for the entire IDE.

To enable Power Save Mode call File | Power Save Mode.

CLion incorporates a complementary Clangd-based language engine which is enabled by default. Currently, it works for error/warning annotation, certain navigation tasks, code formatting via ClangFormat, and code highlighting with quick-fixes.

In most cases, Clangd-based engine works faster than the built-in one (and sometimes provides more accurate results). However, it is not used for all operations. For example, Clangd provides the location for a quick-fix, while the fix itself is performed by the CLion’s own engine. Or, Find Usages employs Clangd to search through the files currently opened in the editor and the CLion’s own engine for all other usages.

We recommend you take Clangd engine specifics into account when investigating performance issues. Use Settings | Languages & Frameworks | C/C++ | Clangd to experiment with the engine settings and see if they affect the performance on certain tasks.

By default, CLion indexes all the directories listed in CMakeLists.txt (sources and include_directories paths) for the purpose of correct resolve.

Your project may contain folders with binaries, logs, or build artifacts, which do not affect CLion code insight. Also, indexing some folders can be too expensive due to their size or location. So it is reasonable to exclude such folders manually: right-click the directory in the project tree and select Mark Directory as | Excluded.

Since the symbols from the excluded files remain uncompleted for CLion, the following features are not available for such files: code completion and auto-import (except for the case when the excluded directory is marked with include_directories in CMakeLists.txt) , code generation, Find in Files (except for the scope of the currently opened files), navigation, and refactorings.

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If you are working in remote development mode, the directories you mark as excluded will not be synchronized with the remote machine. See Remote with local sources: excluded paths.

Another way to eliminate files like logs or generated data from indexing is to exclude them by file type in Settings | Editor | File Types:

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You can also exclude directories from test indexing without excluding them from the regular IDE index. See Speed up tests indexing.

The scope of files being parsed is determined by the loaded CMake script. So if your project is split into several subdirectories with self-contained CMakeLists.txt in each of them, you can load smaller subprojects separately (for this, run Load CMake project on sub-CMakeLists.txt):

Another alternative for the case when you need to explore only a part of a big project is to create a compilation database, reduce it to the part of interest, and then open as a project in CLion.

IDE freezes may happen during the parsing of intricate preprocessor macros. To eliminate such problematic definitions from your code, replace them with some dummy ones using the __CLION_IDE__ (or __JETBRAINS_IDE__) macro:

This macro affects parsing only, and it is undefined when you build or run your code.