8283223: gc/stringdedup/TestStringDeduplicationFullGC.java#Parallel failed with "RuntimeException: String verification failed"

Reviewed-by: tschatzl, kbarrett

test/hotspot/jtreg/gc/stringdedup/TestStringDeduplicationTools.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -31,6 +31,8 @@ import com.sun.management.GarbageCollectionNotificationInfo;
 import java.lang.reflect.*;
 import java.lang.management.*;
 import java.util.*;
+import java.util.stream.Collectors;
+
 import javax.management.*;
 import javax.management.openmbean.*;
 import jdk.test.lib.process.ProcessTools;
@@ -85,6 +87,32 @@ class TestStringDeduplicationTools {
         }
     }
 
+    /**
+     * Get system load.
+     *
+     * <dl>
+     *   <dt>load() ~=   1 </dt><dd> fully loaded system, all cores are used 100%</dd>
+     *   <dt>load() &lt; 1 </dt><dd> some cpu resources are available</dd>
+     *   <dt>load() &gt; 1 </dt><dd> system is overloaded</dd>
+     * </dl>
+     *
+     * @return the load of the system or Optional.empty() if the load can not be determined.
+     */
+    private static Optional<Double> systemLoad() {
+        OperatingSystemMXBean bean = ManagementFactory.getPlatformMXBean(OperatingSystemMXBean.class);
+        double average = bean.getSystemLoadAverage() / bean.getAvailableProcessors();
+        return (average < 0)
+            ? Optional.empty()
+            : Optional.of(average);
+    }
+
+    private static String minMax(List<Optional<Double>> l) {
+        DoubleSummaryStatistics minmax = l.stream().flatMap(Optional::stream).collect(Collectors.summarizingDouble(d -> d));
+        return minmax.getCount() != 0
+            ? "min: " + minmax.getMin() + ", max: " + minmax.getMax()
+            : "could not gather load statistics from system";
+    }
+
     private static void doFullGc(int numberOfTimes) {
         List<List<String>> newStrings = new ArrayList<List<String>>();
         for (int i = 0; i < numberOfTimes; i++) {
@@ -179,13 +207,15 @@ class TestStringDeduplicationTools {
         }
     }
 
-    private static boolean waitForDeduplication(String s1, String s2) {
+    private static void waitForDeduplication(String s1, String s2) {
         boolean first = true;
         int timeout = 10000;     // 10sec in ms
         int iterationWait = 100; // 100ms
+        List<Optional<Double>> loadHistory = new ArrayList<>();
         for (int attempts = 0; attempts < (timeout / iterationWait); attempts++) {
+            loadHistory.add(systemLoad());
             if (getValue(s1) == getValue(s2)) {
-                return true;
+                return;
             }
             if (first) {
                 System.out.println("Waiting for deduplication...");
@@ -194,10 +224,10 @@ class TestStringDeduplicationTools {
             try {
                 Thread.sleep(iterationWait);
             } catch (Exception e) {
-                throw new RuntimeException(e);
+                throw new RuntimeException("Deduplication has not occurred: Thread.sleep() threw", e);
             }
         }
-        return false;
+        throw new RuntimeException("Deduplication has not occurred, load history: " + minMax(loadHistory));
     }
 
     private static String generateString(int id) {
@@ -240,7 +270,9 @@ class TestStringDeduplicationTools {
      */
     private static void verifyStrings(ArrayList<String> list, int uniqueExpected) {
         boolean passed = false;
+        List<Optional<Double>> loadHistory = new ArrayList<>();
         for (int attempts = 0; attempts < 10; attempts++) {
+            loadHistory.add(systemLoad());
             // Check number of deduplicated strings
             ArrayList<Object> unique = new ArrayList<Object>(uniqueExpected);
             for (String string: list) {
@@ -277,7 +309,7 @@ class TestStringDeduplicationTools {
             }
         }
         if (!passed) {
-            throw new RuntimeException("String verification failed");
+            throw new RuntimeException("String verification failed, load history: " + minMax(loadHistory));
         }
     }
 
@@ -361,9 +393,7 @@ class TestStringDeduplicationTools {
             // and be inserted into the deduplication hashtable.
             forceDeduplication(ageThreshold, FullGC);
 
-            if (!waitForDeduplication(dupString1, baseString)) {
+            waitForDeduplication(dupString1, baseString);
-                throw new RuntimeException("Deduplication has not occurred");
-            }
 
             // Create a new duplicate of baseString
             StringBuilder sb2 = new StringBuilder(baseString);
@@ -398,9 +428,7 @@ class TestStringDeduplicationTools {
 
             forceDeduplication(ageThreshold, FullGC);
 
-            if (!waitForDeduplication(dupString3, internedString)) {
+            waitForDeduplication(dupString3, internedString);
-                throw new RuntimeException("Deduplication has not occurred for string 3");
-            }
 
             if (afterInternedValue != getValue(dupString2)) {
                 throw new RuntimeException("Interned string value changed");