Tuning tips for the masses The overall heap size cannot be more than the amount of physical RAM available. You must leave some physical RAM available on your PC for other apps to execute. Set Xms and Xmx to the same value for optimal performance. These parameters define the total size of your heap. They can be any positive number, but there are restrictions on what values they can take.
The first thing to understand about tuning is that it's not a single step process. It's a gradual improvement of your application over time that requires attention to many factors beyond just heap size. For example, when making changes to your heap size, you should also monitor other system resources such as memory usage, CPU percentage, and so on. If you don't, you may end up with an inefficient application that uses too much memory or suffers from other problems caused by misconfigured heap sizes.
Heap size is one of the most important settings to tune in Java, but it's not the only one. There are several others including maximum thread stack size, message buffer size, and so on. Each setting has its own optimum value that depends on how you plan to use your app. Some applications require very large heaps while others can run fine with relatively small ones. Finding the right balance between speed and efficiency is part art, part science. Here are some basic guidelines: if you have enough memory, use it all; otherwise, don't worry about wasting space.
To increase the heap size of the Application Server JVM,
The maximum heap size is around 2 GB (2048MB). However, most applications will not need this much space.
It is important to note that the default heap size for. NET applications is 1GB. If your application needs more than this amount of memory, you will have to specify a custom value when creating an instance of the MemoryManager class.
For example, here is how you could allocate 5GB of memory:
var mm = new MemoryManager(5 * 1024 * 1024);
Consider the heap to be a "free pool" of memory that you may utilize to execute your program. The size of an application's heap is limited by the physical restrictions of your RAM (random access memory) and is often significantly greater than the stack. The malloc method is used to allocate memory from the heap. It returns a pointer to the allocated memory.
On most systems, the stack is a contiguous block of virtual memory reserved for local variables and function arguments. The stack grows downward, meaning it gets smaller as more methods are called. Each time a method is called, its arguments are pushed onto the stack. When the method returns, its results are retrieved from the stack in the order that they were pushed down. Because parameters are stored on the stack, this means that older information must be deleted first before new information can be pushed down.
Heaps and stacks have the same basic structure: A container with a fixed maximum size into which data is inserted via an insertion-sort-like process and from which data is extracted using a removal-sort-like process. However, heaps use global allocation schemes where as stacks allocate memory dynamically via calls to the malloc method.
Heaps and stacks also have different performance characteristics. Heaps usually have better performance when inserting or extracting elements far away from the end of the array because there are no moving parts involved.