Jvm Based Memory Management Quiz

When a Java program starts, it requires memory to execute. This memory is allocated by the Java Virtual Machine (JVM) from the operating system. The JVM is responsible for managing the memory, executing the program, and providing a runtime environment for Java applications. Therefore, the correct answer is JVM.

The JVM memory consists of three segments: JVM Code, Non-Heap Memory, and Heap Memory. The JVM Code segment stores the bytecode and compiled code of the Java program. The Non-Heap Memory segment includes memory areas for the method area, thread stacks, and direct memory. The Heap Memory segment is where objects are allocated and deallocated during program execution. Therefore, all of the above segments are part of the JVM memory.

IBM's JVM, specifically the IBM J9 JVM, allocates large objects directly in the tenured space. This means that when a large object is created, it is directly allocated in the tenured generation of the JVM's memory heap, rather than first being allocated in the young generation and then promoted to the tenured space. This approach can improve performance and reduce memory fragmentation.

The default ratio for eden to old for Oracle JVM is 1:2. This means that the size of the eden space, which is where new objects are created, is half the size of the old space, which is where long-lived objects are stored. This ratio is commonly used to optimize memory allocation and garbage collection in Java applications.

IBM JVM and JRockit JVM do not have the PermGen concept. PermGen (Permanent Generation) is a part of the Java heap memory that is used for storing metadata about classes, methods, and other resources. However, in IBM JVM and JRockit JVM, the PermGen concept is not present. This means that these JVMs do not allocate a separate memory space for storing class metadata, unlike Oracle JVM. Therefore, the correct answer is IBM & JRockit.

If the stack size is too big, it will throw a java.lang.OutOfMemoryError. This error occurs when the JVM (Java Virtual Machine) is unable to allocate enough memory for the stack, resulting in a stack overflow. This can happen if the application or program being executed requires more stack space than is available.

IBM's JVM follows the Allocate->Survivor->Tenured process.

The correct answer is "All the above." This is because all three companies, IBM, Oracle, and JRockit, follow the "Generational Heap Strategy" concept in their JVMs. The generational heap strategy divides the heap into multiple generations, such as young and old generations, to optimize garbage collection and improve performance.

In general, the XMS value should be lower than the XMX value. This is because XMS represents the initial memory allocation for a Java application, while XMX represents the maximum memory allocation. It is common practice to set XMS to a lower value than XMX to ensure that the application starts with a smaller memory footprint and gradually increases its memory usage as needed. Similarly, the XMN value should also be lower than XMX as XMN represents the minimum memory allocation for the young generation in Java's garbage collection algorithm.

The JVM option "XMN" is used for configuring the size of the Young generation, which is the area in memory where newly created objects are allocated. The "Newratio" option, on the other hand, is used to configure the ratio between the Young and Tenured generations. The "XSS" option is used for configuring the thread stack size, and the "XMX" option is used for configuring the maximum heap size.