Parallel: Parellel GC resizes heap too aggressive

Our application is transaction based. Upon finishing a transaction, it is likely to release quite amount of memory. If a GC happens, it likely shrinks heap. Once a new transaction starts to execute, heap starts to expand again. Shrinking and expanding heap are expensive and unnecessary, also impacts on pause time (I would like to measure in next a few days)
 
While we can now workaround it by setting -Xms = -Xmx after JDK-8332418, I believe we should still fix it.