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File: Garbage ...

Ideally, the instances created gets collected at some point by the garbage collector, and since there is a LOT of idle time in the application it would just be dandy if the GC could, well, finish it`s cleanup and actually delete the file on disk as well when dereferencing the instance from memory.

File: Garbage ...

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In the common language runtime (CLR), the garbage collector (GC) serves as an automatic memory manager. The garbage collector manages the allocation and release of memory for an application. Therefore, developers working with managed code don't have to write code to perform memory management tasks. Automatic memory management can eliminate common problems such as forgetting to free an object and causing a memory leak or attempting to access freed memory for an object that's already been freed.

As an application developer, you work only with virtual address space and never manipulate physical memory directly. The garbage collector allocates and frees virtual memory for you on the managed heap.

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 on a thread's stack, CPU registers, GC handles, and the finalize queue. Each root either refers to an object on the managed heap or is set to null. The garbage collector can ask the rest of the runtime for these roots. The garbage collector uses this list to create a graph that contains all the objects that are reachable from the roots.

Objects that aren't in the graph are unreachable from the application's roots. The garbage collector considers unreachable objects garbage and releases the memory allocated for them. During a collection, the garbage collector examines the managed heap, looking for the blocks of address space occupied by unreachable objects. As it discovers each unreachable object, it uses a memory-copying function to compact the reachable objects in memory, freeing up the blocks of address spaces allocated to unreachable objects. Once the memory for the reachable objects has been compacted, the garbage collector makes the necessary pointer corrections so that the application's roots point to the objects in their new locations. It also positions the managed heap's pointer after the last reachable object.

To improve performance, the runtime allocates memory for large objects in a separate heap. The garbage collector automatically releases the memory for large objects. However, to avoid moving large objects in memory, this memory is usually not compacted.

The GC.Collect method is called. In almost all cases, you don't have to call this method because the garbage collector runs continuously. This method is primarily used for unique situations and testing.

After the CLR initializes the garbage collector, it allocates a segment of memory to store and manage objects. This memory is called the managed heap, as opposed to a native heap in the operating system.

To reserve memory, the garbage collector calls the Windows VirtualAlloc function and reserves one segment of memory at a time for managed applications. The garbage collector also reserves segments as needed and releases segments back to the operating system (after clearing them of any objects) by calling the Windows VirtualFree function.

The size of segments allocated by the garbage collector is implementation-specific and is subject to change at any time, including in periodic updates. Your app should never make assumptions about or depend on a particular segment size, nor should it attempt to configure the amount of memory available for segment allocations.

The fewer objects allocated on the heap, the less work the garbage collector has to do. When you allocate objects, don't use rounded-up values that exceed your needs, such as allocating an array of 32 bytes when you need only 15 bytes.

When a garbage collection is triggered, the garbage collector reclaims the memory that's occupied by dead objects. The reclaiming process compacts live objects so that they're moved together, and the dead space is removed, thereby making the heap smaller. This process ensures that objects that are allocated together stay together on the managed heap to preserve their locality.

Garbage collection primarily occurs with the reclamation of short-lived objects. To optimize the performance of the garbage collector, the managed heap is divided into three generations, 0, 1, and 2, so it can handle long-lived and short-lived objects separately. The garbage collector stores new objects in generation 0. Objects created early in the application's lifetime that survive collections are promoted and stored in generations 1 and 2. Because it's faster to compact a portion of the managed heap than the entire heap, this scheme allows the garbage collector to release the memory in a specific generation rather than release the memory for the entire managed heap each time it performs a collection.

If an application attempts to create a new object when generation 0 is full, the garbage collector performs a collection to free address space for the object. The garbage collector starts by examining the objects in generation 0 rather than all objects in the managed heap. A collection of generation 0 alone often reclaims enough memory to enable the application to continue creating new objects.

After the garbage collector performs a collection of generation 0, it compacts the memory for the reachable objects and promotes them to generation 1. Because objects that survive collections tend to have longer lifetimes, it makes sense to promote them to a higher generation. The garbage collector doesn't have to reexamine the objects in generations 1 and 2 each time it performs a collection of generation 0.

If a collection of generation 0 doesn't reclaim enough memory for the application to create a new object, the garbage collector can perform a collection of generation 1 and then generation 2. Objects in generation 1 that survive collections are promoted to generation 2.

Garbage collections occur in specific generations as conditions warrant. Collecting a generation means collecting objects in that generation and all its younger generations. A generation 2 garbage collection is also known as a full garbage collection because it reclaims objects in all generations (that is, all objects in the managed heap).

When the garbage collector detects that the survival rate is high in a generation, it increases the threshold of allocations for that generation. The next collection gets a substantial size of reclaimed memory. The CLR continually balances two priorities: not letting an application's working set get too large by delaying garbage collection and not letting the garbage collection run too frequently.

Ephemeral generations are allocated in the memory segment that's known as the ephemeral segment. Each new segment acquired by the garbage collector becomes the new ephemeral segment and contains the objects that survived a generation 0 garbage collection. The old ephemeral segment becomes the new generation 2 segment.

The size of the ephemeral segment varies depending on whether a system is 32-bit or 64-bit and on the type of garbage collector it's running (workstation or server GC). The following table shows the default sizes of the ephemeral segment:

The amount of freed memory from an ephemeral garbage collection is limited to the size of the ephemeral segment. The amount of memory that's freed is proportional to the space that was occupied by the dead objects.

A compacting phase that reclaims the space occupied by the dead objects and compacts the surviving objects. The compacting phase moves objects that have survived a garbage collection towards the older end of the segment.

Stack roots: Stack variables provided by the just-in-time (JIT) compiler and stack walker. JIT optimizations can lengthen or shorten regions of code within which stack variables are reported to the garbage collector.

For most of the objects your application creates, you can rely on garbage collection to perform the necessary memory management tasks automatically. However, unmanaged resources require explicit cleanup. The most common type of unmanaged resource is an object that wraps an operating system resource, such as a file handle, window handle, or network connection. Although the garbage collector can track the lifetime of a managed object that encapsulates an unmanaged resource, it doesn't have specific knowledge about how to clean up the resource.

This page contains information about settings for the .NET runtime garbage collector (GC). If you're trying to achieve peak performance of a running app, consider using these settings. However, the defaults provide optimum performance for most applications in typical situations.

When a 64-bit Windows computer has multiple CPU groups, that is, there are more than 64 processors, enabling this element extends garbage collection across all CPU groups. The garbage collector uses all cores to create and balance heaps.

Memory load is indicated by the percentage of physical memory in use. By default, when the physical memory load reaches 90%, garbage collection becomes more aggressive about doing full, compacting garbage collections to avoid paging. When memory load is below 90%, GC favors background collections for full garbage collections, which have shorter pauses but don't reduce the total heap size by much. On machines with a significant amount of memory (80GB or more), the default load threshold is between 90% and 97%. 041b061a72


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