Shulou(Shulou.com)06/01 Report--

This article introduces the relevant knowledge of "how to solve the problem of compression pointer enabled by JDK by default". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Starting from JDK5, Sun's HotSpot VM automatically sets some parameters (ergonomics) of VM according to the running environment. Perhaps the most familiar is that it automatically selects client and server modes, heap initialization and * size, and so on. In fact, ergonomics sets a lot of internal parameters, including the automatic selection of GC algorithm, the number of threads in parallel GC, the size of GC's workspace chunks, object promotion threshold, and so on.

Most of the Ergonomics-related logic is in hotspot/src/share/vm/runtime/arguments.cpp, and it's worth noting that FLAG_SET_ERGO () is used.

So we can notice the differences in the handling of UseCompressedOops parameters in several versions of HotSpot:

HotSpot 16:

C++ Code

# ifdef _ LP64 / / Check that UseCompressedOops can be set with the max heap size allocated / / by ergonomics. If (MaxHeapSize

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