From b3aa0cfb93ffc2b6e4ada87ecba6f254e4711cf0 Mon Sep 17 00:00:00 2001
From: Vladislav Beskrovny <vladislav.beskrovny@jetbrains.com>
Date: Tue, 18 Mar 2025 19:22:08 +0100
Subject: [PATCH] [platform] IJPL-181469 Run JBR `shrinkingGC()` when IDE
 becomes idle

A `System.gc()` invocation can lead to the heap being shrunk based on
 the percentage of free memory.
If the free memory percentage is higher than `-XX:MaxHeapFreeRatio`
 (70% by default), the heap is shrunk so that the percentage of free
 heap space is lower than `-XX:MaxHeapFreeRatio`.

The recently introduced `shrinkingGC()` is mostly equivalent to `System.gc()`
 except it shrinks the heap respecting `-XX:JbrShrinkingGcMaxHeapFreeRatio`
 option instead of `-XX:MaxHeapFreeRatio`.

With `-XX:JbrShrinkingGcMaxHeapFreeRatio=40` set, `shrinkingGC()`
 can shrink almost 2 times more than `System.gc()`

GitOrigin-RevId: 5810093ee76baba2babb2a56f74bb02414c6d1c1
---
 .../intellij/build/impl/VmOptionsGenerator.kt          |  1 +
 .../src/com/intellij/ide/AppIdleMemoryCleaner.kt       | 10 +++++++++-
 .../devkit-core/src/run/DevKitApplicationPatcher.kt    |  3 +++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/platform/build-scripts/src/org/jetbrains/intellij/build/impl/VmOptionsGenerator.kt b/platform/build-scripts/src/org/jetbrains/intellij/build/impl/VmOptionsGenerator.kt
index 1d65d44045a6..6e350e2ebcfa 100644
--- a/platform/build-scripts/src/org/jetbrains/intellij/build/impl/VmOptionsGenerator.kt
+++ b/platform/build-scripts/src/org/jetbrains/intellij/build/impl/VmOptionsGenerator.kt
@@ -14,6 +14,7 @@ object VmOptionsGenerator {
 
   @Suppress("SpellCheckingInspection")
   private val COMMON_VM_OPTIONS: List<String> = listOf(
+    "-XX:JbrShrinkingGcMaxHeapFreeRatio=40", // IJPL-181469. Used in a couple with AppIdleMemoryCleaner.runGc()
     "-XX:ReservedCodeCacheSize=512m",
     "-XX:+HeapDumpOnOutOfMemoryError",
     "-XX:-OmitStackTraceInFastThrow",
diff --git a/platform/platform-impl/src/com/intellij/ide/AppIdleMemoryCleaner.kt b/platform/platform-impl/src/com/intellij/ide/AppIdleMemoryCleaner.kt
index 6bd0898b7ad1..b6905c7053ac 100644
--- a/platform/platform-impl/src/com/intellij/ide/AppIdleMemoryCleaner.kt
+++ b/platform/platform-impl/src/com/intellij/ide/AppIdleMemoryCleaner.kt
@@ -28,6 +28,8 @@ import com.intellij.platform.ide.progress.updates
 import com.intellij.util.io.DirectByteBufferAllocator
 import com.intellij.util.io.StorageLockContext
 import com.intellij.util.io.storage.HeavyProcessLatch
+import com.jetbrains.Extensions
+import com.jetbrains.JBR
 import fleet.kernel.rete.asValuesFlow
 import fleet.kernel.rete.tokensFlow
 import fleet.kernel.tryWithEntities
@@ -129,7 +131,13 @@ class AppIdleMemoryCleaner(private val cs: CoroutineScope) {
   private fun runGc() {
     // `System.gc()` makes the heap to shrink respecting `-XX:MaxHeapFreeRatio` VM option, so some memory is returned to OS.
     // At the same time, it leads to a long GC pause (hundreds of milliseconds). This should be OK since the IDE is idle.
-    System.gc()
+    val jbrSystemUtils = JBR.getSystemUtils(Extensions.SHRINKING_GC)
+    if (jbrSystemUtils != null) {
+      // Used in a couple with `-XX:JbrShrinkingGcMaxHeapFreeRatio` option
+      jbrSystemUtils.shrinkingGC()
+    } else {
+      System.gc()
+    }
   }
 }
 
diff --git a/plugins/devkit/devkit-core/src/run/DevKitApplicationPatcher.kt b/plugins/devkit/devkit-core/src/run/DevKitApplicationPatcher.kt
index 60126d601af8..70b84ba67662 100644
--- a/plugins/devkit/devkit-core/src/run/DevKitApplicationPatcher.kt
+++ b/plugins/devkit/devkit-core/src/run/DevKitApplicationPatcher.kt
@@ -97,6 +97,9 @@ private class DevKitApplicationPatcher : RunConfigurationExtension() {
     if (vmParametersAsList.none { it.startsWith("-Xmx") }) {
       vmParameters.add("-Xmx2g")
     }
+    if (vmParametersAsList.none { it.startsWith("-XX:JbrShrinkingGcMaxHeapFreeRatio=") }) {
+      vmParameters.add("-XX:JbrShrinkingGcMaxHeapFreeRatio=40")
+    }
     if (is17 && vmParametersAsList.none { it.startsWith("-XX:SoftRefLRUPolicyMSPerMB") }) {
       vmParameters.add("-XX:SoftRefLRUPolicyMSPerMB=50")
     }