Fix transient failure in TestObjectAllocationOutsideTLABEvent.

Author: christianhaeubl

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/TlabSupport.java

@@ -409,10 +409,10 @@ public static void resize(IsolateThread thread) {
 
         if (SerialAndEpsilonGCOptions.PrintTLAB.getValue()) {
             Log.log().string("TLAB new size: thread ").zhex(thread)
-                            .string(" target refills: ").unsigned(targetRefills)
-                            .string(" alloc avg.: ").unsigned(allocatedAvg)
-                            .string(" desired size: ").hex(desiredSize.get(thread))
-                            .string(" -> ").hex(alignedNewSize).newline();
+                            .string(", target refills: ").unsigned(targetRefills)
+                            .string(", alloc avg.: ").unsigned(allocatedAvg)
+                            .string(", desired size: ").unsigned(desiredSize.get(thread))
+                            .string(" -> ").unsigned(alignedNewSize).newline();
         }
 
         desiredSize.set(thread, alignedNewSize);
@@ -498,13 +498,13 @@ private static void printStats(IsolateThread thread, UnsignedWord allocatedBytes
 
         long waste = gcWaste.get(thread) + refillWaste.get(thread);
         Log.log().string("TLAB: thread: ").zhex(thread)
-                        .string(" slow allocs: ").unsigned(slowAllocations.get(thread))
-                        .string(" refills: ").unsigned(numberOfRefills.get(thread))
-                        .string(" alloc bytes: ").unsigned(allocatedBytesSinceLastGC)
-                        .string(" alloc avg.: ").unsigned((long) allocatedBytesAvg.getAddress(thread).getAverage())
-                        .string(" waste bytes: ").zhex(waste)
-                        .string(" GC waste: ").unsigned(gcWaste.get(thread))
-                        .string(" refill waste: ").unsigned(refillWaste.get(thread)).newline();
+                        .string(", slow allocs: ").unsigned(slowAllocations.get(thread))
+                        .string(", refills: ").unsigned(numberOfRefills.get(thread))
+                        .string(", alloc bytes: ").unsigned(allocatedBytesSinceLastGC)
+                        .string(", alloc avg.: ").unsigned((long) allocatedBytesAvg.getAddress(thread).getAverage())
+                        .string(", waste bytes: ").unsigned(waste)
+                        .string(", GC waste: ").unsigned(gcWaste.get(thread))
+                        .string(", refill waste: ").unsigned(refillWaste.get(thread)).newline();
     }
 
     static void logTlabChunks(Log log, IsolateThread thread, String shortSpaceName) {

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/events/JfrAllocationEvents.java

@@ -59,7 +59,6 @@ public static void reset() {
     @Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)
     public static void emit(long startTicks, DynamicHub hub, UnsignedWord allocationSize, UnsignedWord tlabSize, boolean allocatedOutsideTlab) {
         if (HasJfrSupport.get()) {
-
             if (allocatedOutsideTlab) {
                 emitObjectAllocationOutsideTLAB(startTicks, hub, allocationSize);
             } else if (tlabSize.notEqual(0)) {

substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestObjectAllocationOutsideTLABEvent.java

@@ -56,27 +56,28 @@ public void test() throws Throwable {
         String[] events = new String[]{JfrEvent.ObjectAllocationOutsideTLAB.getName()};
         Recording recording = startRecording(events);
 
+        /* Do a GC before the allocations to avoid that the GC interferes with the test. */
+        System.gc();
+
         /*
          * Use a separate thread for allocating the objects, to have better control over the TLAB
          * and to make sure the objects are actually allocated outside the TLAB.
          */
         Thread testThread = new Thread(() -> {
-            final long largeObjectThreshold = SerialAndEpsilonGCOptions.LargeArrayThreshold.getValue();
-            final int arraySize = NumUtil.safeToInt(largeObjectThreshold - 1024);
+            int arrayDataSize = arrayDataSizeForOutOfTLABAllocation();
 
-            // Allocate a small object to make sure we have a TLAB.
-            Object o = new Object();
-            GraalDirectives.blackhole(o);
+            /* Allocate a small object to make sure we have a TLAB. */
+            GraalDirectives.blackhole(new Object());
 
-            allocateByteArray(arraySize / Byte.BYTES);
-            allocateCharArray(arraySize / Character.BYTES);
+            /* Allocate large arrays that don't fit into the TLAB. */
+            GraalDirectives.blackhole(allocateByteArray(arrayDataSize / Byte.BYTES));
+            GraalDirectives.blackhole(allocateCharArray(arrayDataSize / Character.BYTES));
         }, TEST_THREAD_NAME);
 
         testThread.start();
         testThread.join();
 
         stopRecording(recording, TestObjectAllocationOutsideTLABEvent::validateEvents);
-
     }
 
     @NeverInline("Prevent escape analysis.")
@@ -89,9 +90,17 @@ private static char[] allocateCharArray(int length) {
         return new char[length];
     }
 
+    /**
+     * Returns the required array data size in bytes such that an array is too large to be allocated
+     * in the TLAB, yet still small enough to fit within an aligned heap chunk.
+     */
+    private static int arrayDataSizeForOutOfTLABAllocation() {
+        long largeObjectThreshold = SerialAndEpsilonGCOptions.LargeArrayThreshold.getValue();
+        return NumUtil.safeToInt(largeObjectThreshold - 512);
+    }
+
     private static void validateEvents(List<RecordedEvent> events) {
-        final long largeObjectThreshold = SerialAndEpsilonGCOptions.LargeArrayThreshold.getValue();
-        final int arrayLength = NumUtil.safeToInt(largeObjectThreshold - 1024);
+        int arrayDataSize = arrayDataSizeForOutOfTLABAllocation();
 
         boolean foundByteArray = false;
         boolean foundCharArray = false;
@@ -105,7 +114,7 @@ private static void validateEvents(List<RecordedEvent> events) {
             long allocationSize = event.<Long> getValue("allocationSize");
             String className = event.<RecordedClass> getValue("objectClass").getName();
 
-            if (allocationSize >= arrayLength) {
+            if (allocationSize >= arrayDataSize) {
                 if (className.equals(char[].class.getName())) {
                     foundCharArray = true;
                 } else if (className.equals(byte[].class.getName())) {
@@ -119,5 +128,4 @@ private static void validateEvents(List<RecordedEvent> events) {
         assertTrue(foundByteArray);
         assertTrue(foundCharArray);
     }
-
 }