Jetbrains Custom VM Options Optimized Configuration: Performance tuning parameters for IntelliJ IDEA. Add these params in idea64.exe.vmoptions or idea.exe.vmoptions file in IntelliJ IDEA. If you are using JDK 8.x, please knock off PermSize and MaxPermSize parameters from the tuning configuration.

webstorm64.vmoptions

# custom WebStorm VM options, this configuration also works well for other IDEs like phpstorm, pycharm..etc.

-Xms1024m
-Xmx2048m
-XX:ReservedCodeCacheSize=240m
-XX:+UseConcMarkSweepGC
-XX:SoftRefLRUPolicyMSPerMB=50
-ea
-Dsun.io.useCanonCaches=false
-Djava.net.preferIPv4Stack=true
-XX:+HeapDumpOnOutOfMemoryError
-XX:-OmitStackTraceInFastThrow
-Dawt.useSystemAAFontSettings=lcd
-Dsun.java2d.renderer=sun.java2d.marlin.MarlinRenderingEngine
-Dide.no.platform.update=true

# custom additions
-XX:NewSize=512m
-XX:MaxNewSize=512m
# -XX:PermSize=512m
# -XX:MaxPermSize=512m
-XX:+UseParNewGC
-XX:ParallelGCThreads=4
-XX:MaxTenuringThreshold=1
-XX:SurvivorRatio=8
-XX:+UseCodeCacheFlushing
-XX:+AggressiveOpts
-XX:+CMSClassUnloadingEnabled
-XX:+CMSIncrementalMode
-XX:+CMSIncrementalPacing
-XX:+CMSParallelRemarkEnabled
-XX:CMSInitiatingOccupancyFraction=65
-XX:+CMSScavengeBeforeRemark
-XX:+UseCMSInitiatingOccupancyOnly
-XX:-TraceClassUnloading
-ea
-Dsun.io.useCanonCaches=false

credits: https://gist.github.com/P7h/4388881#gistcomment-3600538

my custom IntelliJ 2021.1 IDEA VM options

-server
-XX:MetaspaceSize=128M
-XX:MaxMetaspaceSize=512m
-XX:+AlwaysPreTouch
-Xms128m
-Xmx1512m
-XX:ReservedCodeCacheSize=512m
-XX:+UseG1GC
-XX:+UseStringDeduplication
-XX:AutoBoxCacheMax=20000
-ea
-Dsun.io.useCanonCaches=false
-Dsun.awt.keepWorkingSetOnMinimize=true
-Djava.net.preferIPv4Stack=true
-Djdk.http.auth.tunneling.disabledSchemes=""
-Djsse.enablesSNIExtension=false
-XX:+HeapDumpOnOutOfMemoryError
-XX:-OmitStackTraceInFastThrow
-Dfile.encoding=UTF-8
-Dhidpi=true
-Dsun.java2d.uiScale.enabled=false
-Dide.ui.scale=1.0