How to release the memory which is occupied but large object as soon as possible?

Question

I have a method as such

 public void MainMethod()
    {
        while(true)
        {
             var largeObject = GetLargeObject();
             ............
             //some work with this largeObject
             ............
             //how to release the memory from largeObject here
        }
    }

obviously, I will use break in loop.

In that usage of this code, my memory will be full of trash pretty fast. Is there a way to free memory that uses some object (largeObject, for example) without running garbage collector by GC.Collect()? Not just mark this object as one that can be collect by GC, but free the memory? Or GC collects largeObject as soon as iteration is over, cause it's not in use anymore?

As long as I understand the realization of IDisposable and call for Dispose() just mark the object for GC but not free the memory instantly (so the memory will be released when the GC runs)

P.S. don't say me "GC will collect everything for your", I know that

Answer 1

first of all. Large objects, i.e. larger than 85kb, will be allocated on the large object heap (LOH). The large object heap is only collected in gen 2 collections, i.e. collections are expensive. Because of this it is generally recommended to avoid frequent LOH allocations. If at all possible, reuse the same object, or use a memory pool to avoid frequent allocations.

There are no way to explicitly free managed memory without letting the GC do its thing. While the standard recommendation is to leave the GC alone, there are cases where it may make sense to run it manually. Like if you have recently released large amount of memory, and the performance impact of a collection is acceptable at that point in time.

If the object is small enough to fit in the Small object heap then you should not need to worry about it. Gen 1 collections are fairly cheap, and while collections will need to run more frequently if you do many allocations, the time to run a collection is not proportional to the amount of freed memory. That said, reusing memory might still be a good idea.

In the end, if you suspect it is a problem, do some profiling. Some of the profilers give you the time spent in garbage collection, and also the allocation rate. Do not try to fix a imaginary problem before confirming that it actually is a problem, and you can verify that the fix actually is an improvement.