eclipse.ini memory settings

eclipse.ini memory settings

-vmargs-Xms128M-Xmx512M-XX: PermSize = 64M-XX: MaxPermSize = 128M

There are several questions:

1. What is the meaning of each parameter?

2. Why are some machines I will be-Xmx and-XX: MaxPermSize is set to 512M can start after the Eclipse, and some machines can not start?

3. Why the above parameters are written to the eclipse.ini file failed to implement the corresponding Eclipse settings?

Here we have been able to answer

1. What is the meaning of each parameter?

Parameter-vmargs means is to set JVM parameters, so the back of which are the parameters of the JVM, we first look at JVM memory management mechanism, and then explain the meaning of each parameter representative.

Heap (Heap) and non-heap (Non-heap) memory

In accordance with the official statement: Java virtual machine has a heap, the heap is the runtime data area, all the class instances and an array of memory are allocated from here. Heap is a Java virtual machine startup created. Outside of the heap in the JVM memory is called non-heap memory (Non-heap memory). JVM key management can be seen that two types of memory: heap and non-heap. To put it simply is the Java code could be in the heap and the memory is reserved for developers to use; non-heap is the JVM to use for themselves, so methods that, JVM required for internal processing or optimization of memory (such as JIT compiled code cache), each class structure (such as run from time to time the number of pools, fields and methods of data), as well as method and constructor code in the non-heap memory.

Heap memory allocation

JVM initial allocation of memory specified by-Xms, the default is the physical memory of 1 / 64; JVM maximum allocation of memory by the-Xmx specified, the default is the physical memory 1 / 4. Default spare less than 40% of heap memory, JVM heap will be increased until the maximum-Xmx limits; spare more than 70% of heap memory, JVM heap will be reduced until the minimum-Xms restrictions. Therefore, the general set up a server-Xms,-Xmx equal in order to avoid adjustments after each GC heap size.

Non-heap memory allocation

JVM using the-XX: PermSize to set the initial value of non-heap memory, the default is the physical memory of 1 / 64; by XX: MaxPermSize set the maximum size of non-heap memory, the default is the physical memory of 1 / 4.

JVM memory limit (max)

First of all JVM memory limit the actual maximum physical memory (nonsense! Hehe), assuming infinite physical memory, then, JVM memory, the maximum value of a great relationship with the operating system. Simply put, the 32-bit processors, although the controlled memory space is 4GB, but will give a specific operating system restrictions, this limit is generally 2GB-3GB (generally Windows systems under 1.5G-2G, Linux system under 2G-3G), while the 64bit processor, there will be no more than limited.

2. Why are some machines I will be-Xmx and-XX: MaxPermSize is set to 512M can start after the Eclipse, and some machines can not start?

JVM memory management through the introduction of the face that we have learned that contains two kinds of JVM memory: heap memory and non-heap memory, another JVM maximum memory depends primarily on the actual physical memory and operating system. So set the VM parameters causes the program to fail to start mainly for the following reasons:

1) the value of-Xms parameter is greater than-Xmx, or-XX: PermSize is greater than the value of-XX: MaxPermSize;

2)-Xmx values and-XX: MaxPermSize more than the sum of the maximum JVM memory limits, such as the current operating system, the maximum memory limit, or the actual physical memory and so on. Talking about the actual physical memory are required at this point is, if your memory is 1024MB, but it is not used in the actual system may be 1024MB, because it occupied in part by the hardware.

3. Why the above parameters are written to the eclipse.ini file failed to implement the corresponding Eclipse settings?

So why the same parameters in the shortcut or the command line effectively in the eclipse.ini document is invalid it? This is because we do not have to comply with the rules set eclipse.ini file:

Parameters of the value of this form is shaped like a key in the middle there is a space to change their line of writing, if the value has spaces in double quotes, including the need to use them. For instance, we use the-vm C: Javajre1.6.0binjavaw.exe parameter is set to the virtual machine, in the eclipse.ini document should be rewritten like this:

-vm
C:Javajre1.6.0binjavaw.exe

In accordance with the above mentioned, the final parameters eclipse.ini can be written like this:

-vmargs
-Xms128M
-Xmx512M
-XX:PermSize=64M
-XX:MaxPermSize=128M

Actual results can be run through the Eclipse in the Help-About Eclipse SDK window inside the Configuration Details button to view it.

Also must be explained, Eclipse comes with eclipse.ini compressed package contents of the file like this:

-showsplash
org.eclipse.platform
--launcher.XXMaxPermSize
256m
-vmargs
-Xms40m
-Xmx256m

One launcher.XXMaxPermSize (Note that the top of the two connecting lines) with the-XX: MaxPermSize parameter is basically the same meaning, I think the only difference is that the former is the time to start eclipse.exe set the parameters, which is the eclipse used by the JVM parameters. In fact, you can set up a two, so there can be launcher.XXMaxPermSize and the next line to use # comment.

3. Other startup parameters. If you have a dual-core CPU, may be able to try this parameter:

-XX:+UseParallelGC

Let GC faster implementation. (Only JDK 5 years of GC additional parameters)