8223441: HeapMonitorStatArrayCorrectnessTest fails due to sampling determinism
Summary: Added an error loop to help with convergence
Reviewed-by: cjplummer, sspitsyn
--- a/test/hotspot/jtreg/serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorStatArrayCorrectnessTest.java Thu May 09 03:11:56 2019 +0200
+++ b/test/hotspot/jtreg/serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorStatArrayCorrectnessTest.java Wed May 08 20:28:56 2019 -0700
@@ -34,6 +34,7 @@
public class HeapMonitorStatArrayCorrectnessTest {
+ private static final int maxCount = 10;
// Do 100000 iterations and expect maxIteration / multiplier samples.
private static final int maxIteration = 100000;
private static int array[];
@@ -46,6 +47,8 @@
public static void main(String[] args) {
int sizes[] = {1000, 10000, 100000};
+ double expected = 0;
+ int count = 0;
for (int currentSize : sizes) {
System.out.println("Testing size " + currentSize);
@@ -55,35 +58,43 @@
throw new RuntimeException("Should not have any events stored yet.");
}
- // 111 is as good a number as any.
- final int samplingMultiplier = 111;
- HeapMonitor.setSamplingInterval(samplingMultiplier * currentSize);
+ for (count = 1; count < maxCount; count++) {
+ // 111 is as good a number as any.
+ final int samplingMultiplier = 111;
+ HeapMonitor.setSamplingInterval(samplingMultiplier * currentSize);
- HeapMonitor.enableSamplingEvents();
+ HeapMonitor.enableSamplingEvents();
- allocate(currentSize);
+ allocate(currentSize);
- HeapMonitor.disableSamplingEvents();
+ HeapMonitor.disableSamplingEvents();
- // For simplifications, we ignore the array memory usage for array internals (with the array
- // sizes requested, it should be a negligible oversight).
- //
- // That means that with maxIterations, the loop in the method allocate requests:
- // maxIterations * currentSize * 4 bytes (4 for integers)
- //
- // Via the enable sampling, the code requests a sample every samplingMultiplier * currentSize bytes.
- //
- // Therefore, the expected sample number is:
- // (maxIterations * currentSize * 4) / (samplingMultiplier * currentSize);
- double expected = maxIteration;
- expected *= 4;
- expected /= samplingMultiplier;
+ // For simplifications, we ignore the array memory usage for array internals (with the array
+ // sizes requested, it should be a negligible oversight).
+ //
+ // That means that with maxIterations, the loop in the method allocate requests:
+ // maxIterations * currentSize * 4 bytes (4 for integers)
+ //
+ // Via the enable sampling, the code requests a sample every samplingMultiplier * currentSize bytes.
+ //
+ // Therefore, the expected sample number is:
+ // count * (maxIterations * currentSize * 4) / (samplingMultiplier * currentSize);
+ // (count because we can do this multiple times in order to converge).
+ expected = maxIteration * count;
+ expected *= 4;
+ expected /= samplingMultiplier;
- // 10% error ensures a sanity test without becoming flaky.
- // Flakiness is due to the fact that this test is dependent on the sampling interval, which is a
- // statistical geometric variable around the sampling interval. This means that the test could be
- // unlucky and not achieve the mean average fast enough for the test case.
- if (!HeapMonitor.statsHaveExpectedNumberSamples((int) expected, 10)) {
+ // 10% error ensures a sanity test without becoming flaky.
+ // Flakiness is due to the fact that this test is dependent on the sampling interval, which is a
+ // statistical geometric variable around the sampling interval. This means that the test could be
+ // unlucky and not achieve the mean average fast enough for the test case.
+ if (HeapMonitor.statsHaveExpectedNumberSamples((int) expected, 10)) {
+ break;
+ }
+ }
+
+ // If we failed maxCount times, throw the exception.
+ if (count == maxCount) {
throw new RuntimeException("Statistics should show about " + expected + " samples; "
+ " but have " + HeapMonitor.sampledEvents() + " instead for the size "
+ currentSize);