tune memory-related jvm flags for better memory reclamation after build end (relates to MRI-2736)

-- obsolete flags removed
   explicitly specify G1GC as the most optimal for memory reclamation

GitOrigin-RevId: cb7dba8446b9b4003181c9824358bb973bf4b32b

build/jvm-rules/jvm-args.bzl

@@ -1,16 +1,29 @@
 def get_jvm_flags(flags):
     return [
-        # Memory
-        # "-XX:+UseZGC",
-        # "-XX:+ZGenerational",
-        "-Xms4g",
+        # G1GC works best for builds with small to medium amount of changes; returns unused committed heap pages to the OS when idle (JEP 346)
+        "-XX:+UseG1GC",
+        # Grow heap when less than 40% free memory is available; after GC allow max 40% of unused memory and reclaim the rest of committed memory to OS
+        # setting values too low might lead to more frequent GCs during work
+        "-XX:MinHeapFreeRatio=40",
+        "-XX:MaxHeapFreeRatio=40",
+
+        # Generational ZGC works good for bigger builds, but is less optimal for small and medium builds; returns unused committed heap pages to the OS when idle
+        #"-XX:+UseZGC",
+        #"-XX:+ZGenerational",
+        #"-XX:ZUncommitDelay=10",   # reclaim unused memory in 10 secs
+        #"-XX:SoftMaxHeapSize=2g",  # try to keep heap compact under 2 Gbytes
+
         "-Xmx20g",
+        "-Xms256m",
+
         # IJ PSI cache
         "-XX:SoftRefLRUPolicyMSPerMB=50",
-        # Code Cache
-        "-XX:NonProfiledCodeHeapSize=512m",
-        "-XX:ProfiledCodeHeapSize=512m",
-        "-XX:ReservedCodeCacheSize=2048m",
+
+        # Code Cache (JDK defaults are sufficient — 240m total, auto-segmented)
+        #"-XX:NonProfiledCodeHeapSize=512m",
+        #"-XX:ProfiledCodeHeapSize=512m",
+        #"-XX:ReservedCodeCacheSize=2048m",
+
         # Prevent JVM logging warnings and errors to stdout because it breaks the protocol between Bazel and the worker process
         "-XX:+DisplayVMOutputToStderr",
         "-Xlog:disable",
@@ -18,23 +31,17 @@ def get_jvm_flags(flags):
         # Headless
         "-Djava.awt.headless=true",
         "-Dapple.awt.UIElement=true",
-        # IJ PHM
-        "--add-opens=java.base/java.util.concurrent=ALL-UNNAMED",
-        "--add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED",
-        "--add-opens=java.base/java.util.concurrent.locks=ALL-UNNAMED",
-        "--add-opens=java.base/java.nio=ALL-UNNAMED",
+
         # Allow querying OS-specific error message for hardlinks-related error detection on Windows
+        "--add-opens=java.base/java.nio=ALL-UNNAMED",
         "--add-opens=java.base/sun.nio.fs=ALL-UNNAMED",
-        # Apache Arrow, but we already opened java.nio for PHM
-        # "--add-opens=java.base/java.nio=org.apache.arrow.memory.core,ALL-UNNAMED",
+
         # kotlin compiler
         "-Dkotlin.environment.keepalive=true",
-        # temporarily disabled to fix build on Windows, JBR-9260
-        "-Djbr.java.io.use.nio=false",
+
         # https://github.com/netty/netty/issues/11532
         "-Dio.netty.tryReflectionSetAccessible=true",
-        # see TargetConfigurationDigestProperty.KOTLIN_VERSION - we invalidate cache if kotlinc version changed
-        "-Dkotlin.jps.skip.cache.version.check=true",
+
         # Set UTF-8 by default as per https://openjdk.org/jeps/400
         "-Dfile.encoding=UTF-8",
     ] + flags