Chat Question: Memory Limits for 32-bit and 64-bit processes

During our recent blog chat, there were a number of topics that were asked about and I am going to expand on some of them.  The first one is the memory limits for different processes.

This really depends on a few different things.  The architecture of the process (32-bit or 64-bit) and also the architecture of the Operating System the process is running on.  For 32-bit it also depends if you use the /3GB switch or not.

So I broke this up based on these things into the table below, this is the maximum amount of memory available for the process assuming you have that much RAM and Pagefile space.

  32-bit OS 64-bit OS
32-bit process 2 GB 4 GB
32-bit process with /3GB 3 GB N/A
64-bit process N/A 16 TB

These process numbers are contingent on how much RAM and disk space you have, so if you have 4 GB of RAM and 4 GB Pagefile, the total memory of all running processes can’t be greater then 8 GB.

Note: If you let Windows manage your Pagefile size, when you hit this limit, Windows will try to grow your Pagefile as long as there is disk space available.

For the amount a .NET application will use before we can expect to see out of memory, those numbers are:

  32-bit OS 64-bit OS
32-bit process 800-1200 MB 2800 MB
32-bit process with /3GB 1800 MB N/A
64-bit process N/A 2800 MB if using a 4 GB process or more if more RAM (around 70% of RAM + Pagefile)

Keep in mind that although a .NET process can grow this large, if the process is multiple GB in size, it can become very difficult for the Garage Collector to keep up with the memory as Generation 2 will become very large.  I’ll talk about the generations more in an upcoming post.

Hopefully that will clear up how much memory each one uses.

Keep checking the RECAP- ASP.NET Blog Chat to see other topics that Tess or I write about.

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