TeamCity memory allocation: Immediate or on-demand

Question

When setting TeamCity memory via TEAMCITY_SERVER_MEM_OPTS=-Xmx4g, is the memory allocated immediately or only when needed?

Answer

When the -Xmx option is used in the TEAMCITY_SERVER_MEM_OPTS environment variable, it specifies the maximum heap size that the Java Virtual Machine (JVM) can use. However, the memory defined by -Xmx is not allocated immediately. Instead, the JVM starts with a smaller heap size (defined by the -Xms parameter if specified, or defaults to the JVM's initial heap size). The memory usage grows dynamically up to the -Xmx limit as needed during runtime, based on the application's requirements. To allocate a fixed amount of memory at JVM startup, you can use the -Xms option to set the initial heap size to the same value as -Xmx.