Skip to main content

Class Data Sharing

Class data sharing (CDS) a feature introduced in J2SE 5.0 reduces the startup time for Java
programming language applications.

When the JRE is installed on 32-bit platforms using the Sun provided installer, the installer loads a set of
classes from the system jar file into a private internal representation, and dumps that representation to a file,
called a "shared archive".Class data sharing is not supported in Microsoft Windows 95/98/ME.

During subsequent JVM invocations, the shared archive is memory-mapped in, saving the cost of loading those
classes and allowing much of the JVM's metadata for these classes to be shared among multiple JVM processes.

The primary motivation for including CDS in the 5.0 release is the decrease in startup time it provides.
CDS produces better results for smaller applications because it eliminates a fixed cost: that of loading
certain core classes. The smaller the application relative to the number of core classes it uses, the
larger the saved fraction of startup time.


The footprint cost of new JVM instances has been reduced in two ways. First, a portion of the shared archive,
currently between five and six megabytes, is mapped read-only and therefore shared among multiple JVM processes.
Previously this data was replicated in each JVM instance. Second, since the shared archive contains class data
in the form in which the Java Hotspot VM uses it, the memory which would otherwise be required to access the
original class information in rt.jar is not needed. These savings allow more applications to be run concurrently
on the same machine.

Regenerating Shared Archive

To regenerate the share archive use the following command:

java -Xshare:dump

Diagnostic information will be printed as the archive is generated.

Manually Controlling Class Data Sharing

The class data sharing feature is automatically enabled when conditions allow it to be used. The following command
line options are present primarily for diagnostic and debugging purposes and may change or be removed in future
releases.

-Xshare:off
Disable class data sharing.

-Xshare:on
Require class data sharing to be enabled. If it could not be enabled for various reasons, print an error message and exit.

-Xshare:auto
The default; enable class data sharing whenever possible.
Labels:

Comments

Post a Comment

Popular posts from this blog

Listen Hindi Internet Radio Channels on PS3

PS3 is the best gadget i have ever used and its true "It only do everything". Having used it to play games, watch netflix, youtube and see my collection of pictures and listen to songs. I was searching for a way to play radio on PS3 and specifically "Hindi Internet Radio Channels" After spending couple of days, finally I have it working in few easy steps: 1. Download PS3 Media server on you laptop or PC: http://ps3mediaserver.blogspot.com/ 2. Open WEB.conf file of PS3 and add following lines: audiostream.Web,Radio=Desi Radio - www.desi-radio.com,http://76.73.90.27:80/ audiostream.Web,Radio=Desi-Radio - www.desi-radio.com,http://76.73.126.218:80/ 3. Restart PS3 Media Server 4. In your PS3, you should see PS3 Media server, open following path: Web -> Radio You should see "Desi Radio" in list. 5. Click on Desi Radio and you have live hindi songs streaming on your Ps3. I am searching more hindi internet radio channels, will update this blog when i find more...
7 comments
Read more

MQTT : Android step by step guide using Eclipse Paho

For MQTT integration, recently explored Paho Android project, very simple to use, here are the steps: Intialize a client, set required options and connect.     MqttAndroidClient mqttClient = new MqttAndroidClient(BaseApplication.getAppContext(), broker, MQTT_CLIENT_ID);     //Set call back class     mqttClient.setCallback(new MqttCallbackHandler(BaseApplication.getAppContext()));     MqttConnectOptions connOpts = new MqttConnectOptions();     IMqttToken token = mqttClient.connect(connOpts); Subscribe to a topic.     token.setActionCallback(new IMqttActionListener() {       @Override       public void onSuccess(IMqttToken arg0) {            mqttClient.subscribe("TOPIC_NAME" + userId, 2, null, new IMqttActionListener() {                 @Override                 public void ...
Post a Comment
Read more

Learn to Play Keyboard

One day I started searching internet about the same thing, how to play keyboard, went through a number of sites, blogs etc.. etc. But finally i learned it on my own, yes dont get surprised this is truth, because most of the sites will just provide you information on keyboard notes etc. But none of them tell you what goes wrong that you dont end up with success in keyboard playing. Well I am sharing my experience here, along with a couple of steps which I hope will be really helpful to you. Please read it like a story not like a lesson about keyboard learning, this will make it easy for you to learn keyboard. Also, this is for those who are busy with their life but still want to lean to play keyboard. First and foremost thing: a) Keep your keyboard at a place, where you can see it, see it in the morning when you get up, see it easily when you go around in your home, dont dump it into an almirah or trunk, this helps, dont get surprised, because everytime you see it at the back of the min...
5 comments
Read more