An Explanation Of Restrictions Limiting The Java Max Heap (-Xmx) To Around 1500M For 32bit JDK’s On Microsoft Windows [ID 557813.1]

Although the maximum amount of physical memory that can be addressed by a 32 bit address bus is 4Gb,  this space has to include the program code and some data structures required by the operating system (such as the stack space), shared libraries and any variables they define. Such considerations limit how much of the total 4Gb address space can be assigned to the heap area of a running JVM and, in the case of the Microsoft Windows, this limit is generally at 1500M (+/- about 200M).

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