The Road to Responsive IntelliJ-Based IDEs

8 hours ago

JetBrains is improving UI responsiveness in IntelliJ-based IDEs by moving performance-sensitive work off the UI thread to reduce write lock time.
The IntelliJ Platform uses a single read-write lock that prevents simultaneous read and write actions, causing freezes when the UI thread waits for locks.
Background write actions were developed to shift write actions off the UI thread, starting in 2019 but paused due to complexity and resumed in 2022.
A new cancelable lock was created in collaboration with JetBrains Research to support background writes, replacing the old lock that assumed writes only on the UI thread.
Modality-aware locking was introduced to handle modal dialogs and prevent deadlocks when running background write actions during modal interactions.
Compatibility mechanisms were implemented to migrate listeners incrementally, such as in VFS refresh, allowing plugin code to run on the UI thread if needed.
Efforts to reduce lock acquisition on the UI thread include relaxing lock requirements in the editor and delaying asynchronous computations to avoid blocking.
Results show a reduction in UI time spent on write actions, from 1.8276% in 2025.2 to 0.5298% in 2025.3, with ongoing work to further eliminate locking.

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