What are exaclty Large Objects in C#?

Question

Can I call an array of 1 million integers as large object? Or one instance of that object should be > 85 KB to be considered as large object?

If I make an array like int[1000000]. This whole object with each member is treated as one object with size > 85 KB. right?

If I have a class X {int i; string j} .. then List having count > 100000. Will this be saved to LOH?

Basically what I mean is if the size of an object like Class X is say 8.6KB and I make a datastructure like List myList. Then if the list count is 9 then it is not LO but if it has count 10 then it is?

I want a last answer(almost go all the answers): Now I know that array is a collection of pointers of 8 bytes. So an array to be Large object it should have 85000/8 number of elements or more. Is that correct?

Answer 1

Any object larger than 85,000 bytes is considered to a large object and is treated differently during garbage collection. An array can itself be over 85,000 bytes large if all its references (aka pointers) make up that amount.

In case of arrays the actual count is not made up of the size of the objects but their references. Let's say you have an array of Customer, and let's assume that a Customer has 3 integers, each 8 bytes in size, and each reference is also 8 bytes in size. Then an array of 10 Customers actually takes up 80 bytes, not 240. The 24 bytes of each Customer are separate objects.

See this article for further information, and refer also to the Large Object Heap Improvements in .NET 4.5.

Answer 2

If you are asking in context of garbage collection then yes 85 KB would be a big object since big objects are immediately marked as a generation 2 objects.