) Eclipse. ini memory setting parameters

-Vmargs-xms128m-xmx512m-XX: permsize = 64 m-XX: maxpermsize = 128 m

The above is a common eclipse memory setting parameter. The following describes the meanings of each parameter:
-Vmargs:
It means to set JVM parameters, so the following are actually JVM parameters. First, let's take a look at the JVM memory management mechanism, and then explain the meaning of each parameter.
Heap and non-heap memory:
According to the official statement: "A Java virtual machine has a heap. The heap is the runtime data area, and the memory of all class instances and arrays is allocated from this place. The heap is created when the Java Virtual Machine is started ." "Memory outside of the heap in JVM is called non-heap memory )". JVM manages two types of memory: heap and non-heap. In short, heap is Java Code Accessible memory is reserved for developers; non-heap memory is reserved for JVM, therefore, the method area, JVM internal processing or optimization of the required memory (such as the code cache after JIT compilation), each class structure (such as the runtime data pool, field and method data) the methods and constructor code are all in non-heap memory.
Heap Memory Allocation
The initial memory allocated by JVM is specified by-XMS. The default value is 1/64 of the physical memory. The maximum memory allocated by JVM is specified by-xmx. The default value is 1/4 of the physical memory. By default, when the free heap memory is less than 40%, the JVM will increase the heap until the maximum limit of-xmx. When the free heap memory is greater than 70%, the JVM will reduce the minimum limit of heap until-XMS. Therefore, the server generally sets-XMS and-xmx to be equal to each other to avoid adjusting the heap size after each GC.
Non-heap memory allocation
JVM uses-XX: permsize to set the non-heap memory initial value. The default value is 1/64 of the physical memory. The maximum non-heap memory size is set by XX: maxpermsize. The default value is 1/4 of the physical memory.
JVM memory limit (maximum)
First, JVM memory is limited to the actual maximum physical memory (nonsense! If the physical memory is infinitely large, the maximum JVM memory has a great relationship with the operating system. Simply put, although the 32-bit processor has a controllable memory space of 4 GB, the specific operating system will impose a limit, this limit is generally 2 GB-3 GB (1.5 GB-2 GB in windows and 2 GB-3 GB in Linux ), the 64-bit and above processors will not be limited.

Troubleshooting:
Why can I enable eclipse after setting-xmx and-XX: maxpermsize to m, but cannot start some machines?
Through the introduction of JVM memory management, we have learned that JVM memory includes two types: heap memory and non-heap memory. In addition, the maximum JVM memory depends on the actual physical memory and operating system. Therefore, setting VM parameters causesProgramThe following are the main reasons for failed startup:
1) In the parameter, the value of-XMS is greater than-xmx, or the value of-XX: permsize is greater than-XX: maxpermsize;
2)-xmx value and-XX: The sum of maxpermsize exceeds the maximum JVM memory limit, such as the maximum memory limit of the current operating system or the actual physical memory. Speaking of the actual physical memory, it should be noted that if your memory is 1024 MB, but it is not likely to be 1024 MB in the actual system, because some of them are occupied by hardware.