From 9c991cfa525e66bac978bacc65429c8779682f87 Mon Sep 17 00:00:00 2001
From: William Kemper <kemperw@amazon.com>
Date: Fri, 25 Apr 2025 13:36:21 -0700
Subject: [PATCH 1/2] Add test case for compact object headers, increase
 pressure on old generation

---
 .../generational/TestOldGrowthTriggers.java   | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java b/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java
index d8471f2db2f28..195b5913ef15f 100644
--- a/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java
+++ b/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java
@@ -58,14 +58,6 @@ public static void makeOldAllocations() {
                 int replaceIndex = r.nextInt(ArraySize);
                 int deriveIndex = r.nextInt(ArraySize);
                 switch (i & 0x3) {
-                    case 0:
-                        // 50% chance of creating garbage
-                        array[replaceIndex] = array[replaceIndex].max(array[deriveIndex]);
-                        break;
-                    case 1:
-                        // 50% chance of creating garbage
-                        array[replaceIndex] = array[replaceIndex].min(array[deriveIndex]);
-                        break;
                     case 2:
                         // creates new old BigInteger, releases old BigInteger,
                         // may create ephemeral data while computing gcd
@@ -106,5 +98,17 @@ public static void main(String[] args) throws Exception {
                 "-XX:ShenandoahGuaranteedYoungGCInterval=0",
                 "-XX:ShenandoahGuaranteedOldGCInterval=0"
         );
+
+        testOld("-Xlog:gc",
+                "-Xms96m",
+                "-Xmx96m",
+                "-XX:+UnlockDiagnosticVMOptions",
+                "-XX:+UnlockExperimentalVMOptions",
+                "-XX:+UseShenandoahGC",
+                "-XX:ShenandoahGCMode=generational",
+                "-XX:ShenandoahGuaranteedYoungGCInterval=0",
+                "-XX:ShenandoahGuaranteedOldGCInterval=0",
+                "-XX:+UseCompactObjectHeaders"
+        );
     }
 }

From 70b36ac530e0ffa5125e63e4ca1d55d6eef22f11 Mon Sep 17 00:00:00 2001
From: William Kemper <kemperw@amazon.com>
Date: Mon, 28 Apr 2025 15:22:22 -0700
Subject: [PATCH 2/2] Clarify cases with comment

---
 .../gc/shenandoah/generational/TestOldGrowthTriggers.java  | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java b/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java
index 195b5913ef15f..840ceffc4fef9 100644
--- a/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java
+++ b/test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java
@@ -58,15 +58,18 @@ public static void makeOldAllocations() {
                 int replaceIndex = r.nextInt(ArraySize);
                 int deriveIndex = r.nextInt(ArraySize);
                 switch (i & 0x3) {
-                    case 2:
+                    case 0:
                         // creates new old BigInteger, releases old BigInteger,
                         // may create ephemeral data while computing gcd
                         array[replaceIndex] = array[replaceIndex].gcd(array[deriveIndex]);
                         break;
-                    case 3:
+                    case 1:
                         // creates new old BigInteger, releases old BigInteger
                         array[replaceIndex] = array[replaceIndex].multiply(array[deriveIndex]);
                         break;
+                    case 2,3:
+                        // do nothing, let all objects in the array age to increase pressure on old generation
+                        break;
                 }
             }
         }