Finalize is a special method that is automatically called by the garbage collector (GC) before the object is collected. This method is only called by the GC. The destructor in C# is automatically translated into Finalize. You can see the IL code using IDASM where you will see that destructor is renamed to finalize.
When a new object is created, the memory is allocated in the managed heap. If newly created object have a Finalize() method or a destructor then a pointer pointing to that object is put into the finalization queue. Basically, finalization queue is an internal data structure that is controlled and managed by the GC. Hence each pointer in finalization queue points to an object that have its Finalize method call before the memory is reclaimed.
Generations
The heap is organized into generations so it can handle long-lived and short-lived objects. Garbage collection primarily occurs with the reclamation of short-lived objects that typically occupy only a small part of the heap. There are three generations of objects on the heap:
Generation 0: This is the youngest generation and contains short-lived objects. An example of a short-lived object is a temporary variable. Garbage collection occurs most frequently in this generation.
Generation 1: This generation serves as a buffer between short-lived objects and long-lived objects.
Generation 2: This generation holds long-lived objects like a static and global variable, that needs to be persisted for a certain amount of time. Objects which are not collected in generation Zero, are then moved to generation 1, such objects are known as survivors, similarly objects which are not collected in generation One, are then moved to generation 2 and from there onwards objects remain in the same generation.
Before the collections for dead objects, the garbage collector looks into the finalization queue for pointers identifies these objects. If the pointer found, then the pointer is flushed from the finalization queue and append to the freachable queue .The freachable queue is also an internal data structure and controlled by the garbage collector. Now each and every pointer with in the freachable queue will identify an object that is ready to have its Finalize method called.
When a new object is created, the memory is allocated in the managed heap. If newly created object have a Finalize() method or a destructor then a pointer pointing to that object is put into the finalization queue. Basically, finalization queue is an internal data structure that is controlled and managed by the GC. Hence each pointer in finalization queue points to an object that have its Finalize method call before the memory is reclaimed.
Generations
The heap is organized into generations so it can handle long-lived and short-lived objects. Garbage collection primarily occurs with the reclamation of short-lived objects that typically occupy only a small part of the heap. There are three generations of objects on the heap:
Generation 0: This is the youngest generation and contains short-lived objects. An example of a short-lived object is a temporary variable. Garbage collection occurs most frequently in this generation.
Generation 1: This generation serves as a buffer between short-lived objects and long-lived objects.
Generation 2: This generation holds long-lived objects like a static and global variable, that needs to be persisted for a certain amount of time. Objects which are not collected in generation Zero, are then moved to generation 1, such objects are known as survivors, similarly objects which are not collected in generation One, are then moved to generation 2 and from there onwards objects remain in the same generation.
Before the collections for dead objects, the garbage collector looks into the finalization queue for pointers identifies these objects. If the pointer found, then the pointer is flushed from the finalization queue and append to the freachable queue .The freachable queue is also an internal data structure and controlled by the garbage collector. Now each and every pointer with in the freachable queue will identify an object that is ready to have its Finalize method called.
Memory allocation
- Garbage Collector (GC) is the part of the .NET framework that allocates and releases memory for your .NET applications.
- When a new process is started, memory is allocated in to the managed heap.
- Objects are allocated in the heap continuously one after another.
- Memory allocation is a very fast process as it is just the adding of a value to a pointer.
Memory release
The garbage collector's optimizing engine determines the best time to perform a collection based on the allocations being made. When the garbage collector performs a collection, it releases the memory for objects that are no longer being used by the application. It determines which objects are no longer being used by examining the application's roots. An application's roots include static fields, local variables and parameters on a thread's stack, and CPU registers. Each root either refers to an object on the managed heap or is set to null. The garbage collector has access to the list of active roots that the just-in-time (JIT) compiler and the runtime maintain. Using this list, the garbage collector creates a graph that contains all the objects that are reachable from the roots. https://docs.microsoft.com
When GC Gets Triggered?
There are no specific timings for GC to get triggered, GC automatically starts operation on the following conditions:
- When virtual memory is running out of space.
- When allocated memory is suppressed acceptable threshold (when GC found if the survival rate (living objects) is high, then it increases the threshold allocation).
- When we call GC.Collect() method explicitly, as GC runs continuously, we actually do not need to call this method.
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