Test gc/g1/TestStringDeduplicationMemoryUsage.java is still failing due to unexpected memory usage

Test gc/g1/TestStringDeduplicationMemoryUsage.java failed with following exception during PIT for 8u20-b16:

java.lang.Exception: Unexpected memory usage, heapMemoryUsageWithDedup should be less or equal to heapMemoryUsageWithDedupExpected
at TestStringDeduplicationTools.testMemoryUsage(TestStringDeduplicationTools.java:520)
at TestStringDeduplicationMemoryUsage.main(TestStringDeduplicationMemoryUsage.java:34)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.sun.javatest.regtest.MainWrapper$MainThread.run(MainWrapper.java:94)
at java.lang.Thread.run(Thread.java:745)

Memory usage summary:
   heapMemoryUsageWithoutDedup: 1752176
   heapMemoryUsageWithDedup: 655048
   heapMemoryUsageWithDedupExpected: 632288

I was able to reproduce this issue on the same host, but it happened intermittently - it may take from 1 to 10 tries before test fail.