Meaning and setting of the Eclipse.ini parameter

This article describes the meaning and settings of the Eclipse.ini parameter. Eclipse.ini has the following parameters:-vmargs-xms128m-xmx512m-xx:permsize=64m-xx:maxpermsize=128m Here are a few questions: 1.

What each parameter means.

2. Why are there machines I set-XMX and-xx:maxpermsize to 512M after eclipse can be started, and some machines will not start.

　　3. Why write the above parameters to the Eclipse.ini file eclipse does not perform the corresponding settings. Here we answer each of the 1.

　　What each parameter means.

　　The-vmargs in the parameter is to set the JVM parameters, so the following is actually the JVM parameters, we first understand the JVM memory management mechanism, and then explain the meaning of each parameter represents. Heap (heap) and non-heap (non-heap) memory according to the official statement: "Java virtual machines have a heap, the heap is a runtime data region, and all class instances and arrays of memory are allocated from here." The heap is created when the Java Virtual machine is started. "" Memory outside the heap in the JVM is called Non-heap memory (non-heapmemory). " You can see that the JVM primarily manages two types of memory: heap and non-heap. In a nutshell, a heap is a Java code-readable memory that is left to the developer, not a heap, which is left to itself by the JVM, so the method area, the JVM internally processes or optimizes the required memory (such as the JIT-compiled code cache), each class structure (such as running a constant pool, field, and method data)

　　And the code for methods and construction methods are in non-heap memory. The heap memory allocation JVM initially allocates memory specified by-XMS, the default is physical memory 1/64;JVM the maximum allocated memory is specified by-XMX, which defaults to 1/4 of the physical memory. When the default free heap memory is less than 40%, the JVM increases the heap until the maximum limit of-xmx, and when the free heap memory is greater than 70%, the JVM reduces the heap until the minimum limit of-XMS.

　　So the server generally sets-xms,-xmx equal to avoid resizing the heap after each GC.

　　The non-heap memory allocation JVM uses-xx:permsize to set the non-heap memory initial value, which defaults to 1/64 of the physical memory, and by xx:maxpermsize sets the maximum non-heap memory size, which defaults to 1/4 of the physical memory. JVM Memory Limit (max) First JVM memory is limited to the actual maximum physical memory (nonsense. hehe), assuming that the physical memory is infinitely large, the maximum value of the JVM memory is very much related to the operating system. Simply put, 32-bit processor, although the controllable memory spaceThere are 4GB, but the specific operating system will give a limit, this limit is generally 2GB-3GB (generally speaking under the Windows system for the 1.5g-2g,linux system is 2g-3g), and 64bit or more processors will not be limited.

　　2. Why are there machines I set-XMX and-xx:maxpermsize to 512M after eclipse can be started, and some machines will not start. We have learned from the above introduction to JVM memory management that there are two types of JVM memory: heap memory and non-heap memory, and the JVM's maximum memory depends first on actual physical memory and operating system. So there are several reasons why setting the VM parameter causes the program not to start: 1) The value of-XMS in the parameter is greater than-XMX, or the value of-xx:permsize is greater than-xx:maxpermsize; 2)-xmx value and-xx: The sum of the maxpermsize exceeds the maximum JVM memory limit, such as the current operating system maximum memory limit, or actual physical memory, and so on.

When it comes to physical memory, it is important to note that if your memory is 1024MB, the actual system is not likely to be 1024MB, because a portion of it is consumed by the hardware.

　　3. Why write the above parameters to the Eclipse.ini file eclipse does not perform the corresponding settings. Why is the same argument valid on a shortcut or command line and is not valid in the Eclipse.ini file? This is because we do not comply with the Eclipse.ini file setting rules: The parameter shape, such as "key value" in this form, there are spaces in the middle of the need to write a newline, if the value of a space in the need to be enclosed in double quotation marks. For example, we use the-vmc:\java\jre1.6.0\bin\javaw.exe parameter to set up the virtual machine, in the Eclipse.ini file to write this:-VM C:\Java\jre1.6.0\bin\javaw.exe according to the above, the most The following parameters can be written in Eclipse.ini:-vmargs-xms128m-xmx512m-xx:permsize=64m-xx:maxpermsize=128m The actual results can be obtained by ECL

　　Ipse "Help"-the "about ECLIPSESDK" window inside the "configurationdetails" button to view.

　　It is also necessary to note that the contents of the Eclipse.ini file included in the Eclipse compression package are as follows:-showsplashOrg.eclipse.platform--launcher. Xxmaxpermsize 256m-vmargs-xms40m-xmx256m which –launcher. Xxmaxpermsize (Note that the front is two connectors) the meaning of the-xx:maxpermsize parameter is basically the same, I think the only difference is that the former is the parameter set when the Eclipse.exe is started, and the latter is the parameter in the JVM used by Eclipse. In fact, the two set a can, so here can put –launcher.

　　Xxmaxpermsize and Next line use # comment out. 3. Other start-up parameters. If you have a dual-core CPU, you might be able to try this parameter:-XX:+USELLELGC allows the GC to execute faster. (Just a new addition to the GC in JDK 5) What you are reading is: Eclipse.ini parameter editing recommended Tomcat to start timeouts in Eclipse solution improve code quality with Eclipse plug-in to help you configure development in eclipse Struts installs the Eclipse plug-in and installation configuration method required for Tomcatplugin JSP development in Eclipse