How to Increase IntelliJ IDEA Memory Allocation to Eliminate Lag

Hello everyone, I’m Lei.

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When developing with IntelliJ IDEA you may experience occasional freezes even on a high‑spec machine. The root cause is that IDEA sets a very low default maximum heap size (often 1 GB) during installation, which quickly becomes a bottleneck when running large projects.

You can view the current memory consumption of your project via the IDE’s memory indicator.

In my case the program uses about 690 MB while the limit is 1024 MB, which is insufficient during performance spikes. You can change these limits in IDEA’s settings.

Specific steps (three steps)

1. In the top menu choose Help → Edit Custom VM Options to open the VM options file.

2. The editor shows the current options, for example:

-Xmx1024m    // Maximum heap size: 1024 MB (1 GB)
-Xms256m     // Initial heap size: 256 MB
-XX:ReservedCodeCacheSize=128m    // Code cache size: 128 MB
-XX:+UseG1GC

Adjust the values according to your machine (e.g., increase to 4 GB) and save the file:

-Xmx4096m
-Xms4096m
-XX:ReservedCodeCacheSize=256m
-XX:+UseG1GC

3. Clear caches so the new configuration takes effect: choose File → Invalidate Caches , keep the default options, confirm, and restart IDEA.

After restarting, IDEA runs smoothly.

Note: All JetBrains products (PyCharm, Android Studio, WebStorm, etc.) can use the same settings. Below is a brief explanation of common VM parameters:

Parameters explanation:

-server: should be the first argument; improves performance on multi‑CPU systems
-Xms: initial heap size (minimum memory); set larger on high‑performance CPUs
-Xmx: maximum heap size (maximum memory)
-XX:PermSize: size of the permanent generation
-XX:MaxPermSize: maximum size of the permanent generation
-XX:MaxNewSize:
+XX:AggressiveHeap: makes Xms less relevant
-Xss: thread stack size
-verbose:gc: prints garbage collection info
-Xloggc:gc.log: specifies GC log file
-Xmn: size of the young generation (usually 1/3 or 1/4 of Xmx)
-XX:+UseParNewGC: shortens minor GC time
-XX:+UseConcMarkSweepGC: shortens major GC time
(Note: this option is suitable when heap size is large and major GC takes long.)

Source: blog.csdn.net/qq_35760825/article/details/123325533