use compareandset. Add a test for peak tracking.

Author: roberttoyonaga

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/nmt/NmtMallocMemoryInfo.java

@@ -62,12 +62,11 @@ void track(UnsignedWord allocationSize) {
     private void updatePeak(long newUsed, long newCount) {
         long expectedPeakUsage = peakUsage;
         while (expectedPeakUsage < newUsed) {
-            long originalValue = U.compareAndExchangeLong(this, PEAK_USAGE_OFFSET, expectedPeakUsage, newUsed);
-            if (originalValue == expectedPeakUsage) {
+            if (U.compareAndSetLong(this, PEAK_USAGE_OFFSET, expectedPeakUsage, newUsed)) {
                 peakCount = newCount;
-                break;
+                return;
             }
-            expectedPeakUsage = originalValue;
+            expectedPeakUsage = peakUsage;
         }
     }
 

substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/nmt/NativeMemoryTrackingTests.java

@@ -83,6 +83,24 @@ public void testRealloc() {
         assertEquals(0, getUsedMemory());
     }
 
+    @Test
+    public void testPeakTracking() {
+        assertEquals(0, getUsedMemory());
+
+        Pointer ptr1 = NativeMemory.malloc(WordFactory.unsigned(ALLOCATION_SIZE), NmtCategory.Code);
+        long initialPeak = NativeMemoryTracking.singleton().getPeakUsedMemory(NmtCategory.Code);
+        assertTrue(initialPeak > 0);
+
+        Pointer ptr2 = NativeMemory.malloc(WordFactory.unsigned(initialPeak * 2), NmtCategory.Code);
+        long newPeak = NativeMemoryTracking.singleton().getPeakUsedMemory(NmtCategory.Code);
+        assertTrue(newPeak >= initialPeak * 2);
+
+        NativeMemory.free(ptr1);
+        NativeMemory.free(ptr2);
+        assertTrue(NativeMemoryTracking.singleton().getPeakUsedMemory(NmtCategory.Code) == newPeak);
+        assertEquals(0, getUsedMemory());
+    }
+
     private static long getUsedMemory() {
         return NativeMemoryTracking.singleton().getUsedMemory(NmtCategory.Code);
     }