What is the meaning of the parameters of set java_opts?

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What is the meaning of the parameters of set java_opts?

such as the following:

Set java_opts=%java_opts%-xms512m-xmx1024m-xx:permsize=256m-xx:maxpermsize=2

I want to explain it from the JVM's point of view.

Minimum value of the-xms512m heap
Maximum value of the-xmx1024m heap
In addition, the Hotspot garbage collection uses the method of generational collection, which divides the heap into three parts, the new domain, the old domain and the permanent domain. All new objects generated by the JVM are placed in the new domain. Once an object undergoes a certain number of garbage collection loops, it gets the usage period and goes into the old domain. In a permanent domain, the JVM stores the class and method objects. As far as configuration is concerned, the permanent domain is a separate domain and does not feel as part of the heap
-xx:maxpermsize=2 set the maximum value for the permanent domain,
-xx:permsize=256m set the initial value of the permanent domain (your sample is obviously problematic)

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Java_opts

Like what:

-xms512m-xmx512m-xx:maxpermsize=512m-xx:+aggressiveheap

Http://www.blogjava.net/yanzhou/archive/2006/09/13/69384.aspx:

-xms 520m-xmx 1220M-XSS 15120k +xx:aggressiveheap

1. +xx:aggressiveheap will make Xms 1220m meaningless. This parameter allows the JVM to ignore xmx parameters, frantically eats a g of physical memory, and eats a G swap.
In addition, xmx as the maximum amount of memory that the JVM uses, should not exceed 90% of the physical memory.
The use of this parameter is due to the lack of the word, JBoss will be in the execution of a day or so after the rapid collapse of the machine class is, even a half an hour after the collapse of the situation.
The reason to use this parameter is to use swap to support server execution because of the following error:
2.-XSS 15120k
This causes JBoss to consume 15M of memory at once for each thread that is added, and the best value should be 128K, and the default value is like 512k.
This is when JBoss was started, there was a surplus of 200Mb of memory, but it was quickly exhausted within one hours, as the server's threads was quickly added. In the first 3 days, eat more than 80Mb of swap every day. On the fourth day, it started to stabilize. This year's holiday in the Spring Festival, observed this phenomenon, but do not understand the reason: server thread reached 100, generally no longer add new threads, newly added in the use of the end will be quickly destroy,?? Coat Mei which Axmanovs is not education to play? Axmanovs Chan Xu aftertaste? bld Lan pepper? Geumcheon the thread used for the operation is basically 髟 created, so no new memory is consumed. Server execution time, and therefore greatly exceeded my 5 days of expectations, arrived 20 days.

Changes made yesterday:
1. Change java_opts, remove +xx:aggressiveheap, change XSS. Today's java_opts are:
-xms 520m-xmx 900M-XSS 128k
2. Change Deploy/jbossweb-tomcat55.sar/service.xml
The maxthreads based on the current number of visits from the default of 250 down to 75, and using JBoss 4 default is not written in the standard Service.xml, and JBoss 3 wrote the 2 parameters: maxsparsethreads= 55,minsparsethreads=25
3. Changed the Oracle-ds.xml to reduce the maximum number of connections by 150 to 50.
4. Some unused services have been removed.

What do the parameters of set java_opts mean?