8038461: Test gc/g1/TestStringDeduplicationMemoryUsage.java fails with unexpected memory usage
Reviewed-by: jmasa, sjohanss
diff --git a/hotspot/test/gc/g1/TestStringDeduplicationTools.java b/hotspot/test/gc/g1/TestStringDeduplicationTools.java
index 1c1f480..5b27aa6 100644
--- a/hotspot/test/gc/g1/TestStringDeduplicationTools.java
+++ b/hotspot/test/gc/g1/TestStringDeduplicationTools.java
@@ -310,7 +310,9 @@
}
System.gc();
+
System.out.println("Heap Memory Usage: " + ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed());
+ System.out.println("Array Header Size: " + unsafe.ARRAY_CHAR_BASE_OFFSET);
System.out.println("End: MemoryUsageTest");
}
@@ -482,31 +484,40 @@
public static void testMemoryUsage() throws Exception {
// Test that memory usage is reduced after deduplication
OutputAnalyzer output;
- final String usagePattern = "Heap Memory Usage: (\\d+)";
+ final String heapMemoryUsagePattern = "Heap Memory Usage: (\\d+)";
+ final String arrayHeaderSizePattern = "Array Header Size: (\\d+)";
// Run without deduplication
output = MemoryUsageTest.run(false);
output.shouldHaveExitValue(0);
- final long memoryUsageWithoutDedup = Long.parseLong(output.firstMatch(usagePattern, 1));
+ final long heapMemoryUsageWithoutDedup = Long.parseLong(output.firstMatch(heapMemoryUsagePattern, 1));
+ final long arrayHeaderSizeWithoutDedup = Long.parseLong(output.firstMatch(arrayHeaderSizePattern, 1));
// Run with deduplication
output = MemoryUsageTest.run(true);
output.shouldHaveExitValue(0);
- final long memoryUsageWithDedup = Long.parseLong(output.firstMatch(usagePattern, 1));
+ final long heapMemoryUsageWithDedup = Long.parseLong(output.firstMatch(heapMemoryUsagePattern, 1));
+ final long arrayHeaderSizeWithDedup = Long.parseLong(output.firstMatch(arrayHeaderSizePattern, 1));
+
+ // Sanity check to make sure one instance isn't using compressed class pointers and the other not
+ if (arrayHeaderSizeWithoutDedup != arrayHeaderSizeWithDedup) {
+ throw new Exception("Unexpected difference between array header sizes");
+ }
// Calculate expected memory usage with deduplication enabled. This calculation does
// not take alignment and padding into account, so it's a conservative estimate.
- final long sizeOfChar = 2; // bytes
- final long bytesSaved = (LargeNumberOfStrings - 1) * (StringLength * sizeOfChar + unsafe.ARRAY_CHAR_BASE_OFFSET);
- final long memoryUsageWithDedupExpected = memoryUsageWithoutDedup - bytesSaved;
+ final long sizeOfChar = unsafe.ARRAY_CHAR_INDEX_SCALE;
+ final long sizeOfCharArray = StringLength * sizeOfChar + arrayHeaderSizeWithoutDedup;
+ final long bytesSaved = (LargeNumberOfStrings - 1) * sizeOfCharArray;
+ final long heapMemoryUsageWithDedupExpected = heapMemoryUsageWithoutDedup - bytesSaved;
System.out.println("Memory usage summary:");
- System.out.println(" memoryUsageWithoutDedup: " + memoryUsageWithoutDedup);
- System.out.println(" memoryUsageWithDedup: " + memoryUsageWithDedup);
- System.out.println(" memoryUsageWithDedupExpected: " + memoryUsageWithDedupExpected);
+ System.out.println(" heapMemoryUsageWithoutDedup: " + heapMemoryUsageWithoutDedup);
+ System.out.println(" heapMemoryUsageWithDedup: " + heapMemoryUsageWithDedup);
+ System.out.println(" heapMemoryUsageWithDedupExpected: " + heapMemoryUsageWithDedupExpected);
- if (memoryUsageWithDedup > memoryUsageWithDedupExpected) {
- throw new Exception("Unexpected memory usage, memoryUsageWithDedup should less or equal to memoryUsageWithDedupExpected");
+ if (heapMemoryUsageWithDedup > heapMemoryUsageWithDedupExpected) {
+ throw new Exception("Unexpected memory usage, heapMemoryUsageWithDedup should be less or equal to heapMemoryUsageWithDedupExpected");
}
}
}
