Why does the Subphase weak roots JVMTIWeakExport is always increasing?

[苗昌宇]

When I use ZGC on JDK11.0.8 in an online service, I find the time of Subphase weak roots JVMTIWeakExport is always increasing as our service is running. I want to know want made that？
Hope you will teach me. 

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