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8223441: HeapMonitorStatArrayCorrectnessTest fails due to sampling determinism

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Added an error loop to help with convergence

Reviewed-by: cjplummer, sspitsyn
This commit is contained in:
Jean Christophe Beyler 2019-05-08 20:28:56 -07:00
parent 7e4cb52719
commit 608a45ce68
1 changed files with 35 additions and 24 deletions
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59
test/hotspot/jtreg/serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorStatArrayCorrectnessTest.java
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@ -34,6 +34,7 @@ package MyPackage;
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 class HeapMonitorStatArrayCorrectnessTest {
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 @@ public class HeapMonitorStatArrayCorrectnessTest {
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);