Maximum .NET achievable memory?

Question

Which is the maximum amount of memory one can achieve in .NET managed code? Does it depend on the actual architecture (32/64 bits)?

Answer 1

The following blog post has detailed findings on x86 and x64 max memory. It also has a small tool (source available) which allows easy easting of the different memory options: http://www.guylangston.net/blog/Article/MaxMemory.

Answer 2

There are no hard, exact figure for .NET code.

If you run on 32 bit Windows; your process can address up to 2 GB, 3 GB if the /3GB switch is used on Windows Server 2003.

If you run a 64 bit process on a 64 bit box your process can address up to 8 TB of address space, if that much RAM is present.

This is not the whole story however, since the CLR takes some overhead for each process. At the same time, .NET will try to allocate new memory in chunks; and if the address space is fragmented, that might mean that you cannot allocate more memory, even though some are available.

Answer 3

In C# 2.0 and 3.0 there is also a 2G limit on the size of a single object in managed code.

Answer 4

I have recently been doing extensive profiling around memory limits in .NET on a 32bit process. We all get bombarded by the idea that we can allocate up to 2.4GB (2^31) in a .NET application but unfortuneately this is not true :(. The application process has that much space to use and the operating system does a great job managing it for us, however, .NET itself seems to have its own overhead which accounts for aproximately 600-800MB for typical real world applications that push the memory limit. This means that as soon as you allocate an array of integers that takes about 1.4GB, you should expect to see an OutOfMemoryException().

Obviously in 64bit, this limit occurs way later (let's chat in 5 years :)), but the general size of everything in memory also grows (I am finding it's ~1.7 to ~2 times) because of the increased word size.

What I know for sure is that the Virtual Memory idea from the operating system definitely does NOT give you virtually endless allocation space within one process. It is only there so that the full 2.4GB is addressable to all the (many) applications running at one time.

I hope this insight helps somewhat.

I originally answered something related here (I am still a newby so am not sure how I am supposed to do these links):

Is there a memory limit for a single .NET process

Answer 5

I think other answers being quite naive, in real world after 2GB of memory consumption your application will behave really badly. In my experience GUIs generally go massively clunky, unsusable after lots of memory consumptions.

This was my experience, obviously actual cause of this can be objects grows too big so all operations on those objects takes too much time.

Answer 6

Yes, in a 32 bits environment you are limited to a 4GB address-space but Windows claims about half. On a 64 bits architecture it is, well, a lot bigger. I believe it's 4G * 4G

And on the Compact Framework it usually is in the order of a few hundred MB