Mobile devices may have limited resources compared to today's desktop computers, but they still have ample memory. Therefore, effective memory management is not simply about quickly releasing memory. You can use memory to your advantage (e.g. a more fluid user interface) by having a good caching strategy. Just be ready to release this memory, like anything you can recreate, if the operating system asks for it. For example, an often-used view controller, using several small and lightweight objects, might be cheap to cache and reuse. The alternative, disposing and re-creating it each time, would require more allocations (and GC time) and could lead to severe memory fragmentation. Also you risk repeating, several times, any memory leaks or cycles your code might have. However, you cannot implement any caching effectively unless you know the real (memory) cost of what you create. Therefore always measure. It's also very important to test on devices because the emulator or simulator will not provide an accurate representation of a device this article will delve into some of the best practices for effectively using memory and provide tips to help achieve high performance. IOS and OS X users can use Apple Instruments to get accurate memory measurements of their applications, whereas Android users have the Android Device Manager at their disposal.
Managed languages make use of garbage collection to reclaim memory that is allocated to objects that are no longer in use. There are two garbage collectors available with Xamarin.iOS (Xamarin.Android only has SGen):
•Boehm – This is a non-generational garbage collector. It is the default garbage collector used in Xamarin.iOS. When garbage collection occurs, the entire heap will be collected.
•SGen – This is a generational garbage collector and should be preferred over Boehm. This is because SGen, compared to Boehm, performs collections more frequently, and over a smaller set of objectss. This has less of an impact on application performance.

A Quick Overview of the SGen Garbage Collector

SGen utilizes one of three heaps to allocate space for objects:
•The Nursery – This is where small, new objects are allocated. When the nursery runs out of space, a minor garbage collection will occur. Any live objects will be moved to the major heap.
•Major Heap – This is where long running objects are kept. If there is not enough memory in the major heap, then a major garbage collection will occur. If a major garbage collection fails to free up enough memory then SGen will ask the system for more memory.
•Large Object Space – This is where objects that require more than 8000 bytes are kept. Large objects will not start out in the nursery, but instead will be allocated in this heap.