Why Server If It’s Not a Server?
Why Server If It’s Not a Server?
Learn why Server VM is sometimes used, how it determines which JIT compiler and GC are used at runtime by default, and how this affects speed.
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Have you ever wondered why, when you type java -version, you usually get something like this:
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)Why Server VM?
For JVM, some machines are considered to be “client-class” and some are “server-class.” If the given machine is classified as “server-class,” then HotSpot Server VM will be used. For “client-class,” it’s going to be HotSpot Client VM. The type of HotSpot determines which type of JIT compiler and which GC will be used at runtime by default. Because of that, the Server VM starts up more slowly than the Client VM, but over time, runs more quickly.
To check whether the machine is a “client-class” or a “server-class,” you can have a look at the following (a little bit simplified) rules:
CPU with one core |
CPU with multiple cores |
|
32-bit JVM on Windows |
client | client |
32-bit JVM on non-Windows system |
client | server |
64-bit JVM on any system |
server | server |
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