Does processModel memoryLimit apply to ASP.Net only? (System.OutOfMemoryException)

Question

We are running a .Net 1.1 based Windows Service (not an ASP.Net application), and we are getting System.OutOfMemoryException errors under heavy load.

The service basically hosts an in memory cache, consisting of an Asset hashtable, nested within that is an account hashtable, and within that is a class that stores values for a given time period (for the Asset+Account combination). The service serves up aggregates of this data to clients, as well as accepts updates to the data. The total number of nodes remains constant throughout the service lifetime.

In machine.Config, we see things such as:

    <processModel 
       enable="true" 
       timeout="Infinite" 
       idleTimeout="Infinite" 
       shutdownTimeout="00:00:05" 
       requestLimit="Infinite" 
       requestQueueLimit="5000" 
       restartQueueLimit="10" 
       memoryLimit="60" 
       webGarden="false" 
       cpuMask="0xffffffff" 
       userName="machine" 
       password="AutoGenerate" 
/>

These all seem to be related to ASP.Net/IIS applications, but our OutOfMemoryException is not occurring under ASP.Net, and there seems to be no equivalent configuration setting for non ASP applications.

Does this section perhaps apply to all .Net based applications, not just ASP.Net?

I ask because, our service was getting up around 1.2 GB of memory consumption (we are storing a large database in memory, yes, with good reason) when the error occurred, which is coincidentally roughly equal to 60% of 2GB (the memory "limit" of 32 bit applications). Could this apparent IIS config setting be causing our windows service memory to be capped as well?

To complicate matters a bit further, we are running this on .Net 1.1 32 Bit, under 64 Bit Windows Server 2003 (yes, we do have a reason for this unusual configuration), with 12 GB of RAM. From what I understand, each 32 Bit process should be able to address up to 4GB of RAM, should it not? Or, does this require changes to either the registry or a .Net config file?

NOTE: I am aware of the /3GB windows startup switch, but since we are on 64 Bit windows, I don't think that should apply (but feel free to correct me if I'm wrong).

Update 1

People seem to agree that processModel configuration is specific to ASP.Net applications only.

One answer says that 32 bit apps on 64 bit OS still have a 2GB per process limit, but most any reference I have been able to find says that each 32 bit process has access to 4GB on a 64 Bit OS. (But, perhaps this only only enabled through setting the IMAGEFILELARGEADDRESSAWARE bit?)

Some relevant links

How to set the IMAGE_FILE_LARGE_ADDRESS_AWARE bit for C# apps:
http://bytes.com/groups/net-c/569198-net-4gt

IIS6 Available Memory for 32-Bit Application with Web Garden on x64 OS (32Gb Ram):
http://stackoverflow.com/questions/366349/iis6-available-memory-for-32-bit-application-with-web-garden-on-x64-os-32gb-ram

.NET Debugging Demos Lab 3: Memory:
http://blogs.msdn.com/tess/archive/2008/02/15/net-debugging-demos-lab-3-memory.aspx
Should be useful to find the specifics of the OutOfMemoryException?

Pushing the Limits - Virtual Memory:
http://blogs.technet.com/markrussinovich/archive/2008/11/17/3155406.aspx
Read this to understand concepts, and use testlimit to rule out machine/config issues. Once convinced it's your app's fault, read & re-read the articles from Tess' blog.

Final Update

Well, for our situation, this turned out to apparently be missing an .Net Service Pack....apparently there was an issue with remoting getting this exception, after the service pack it cleared up entirely!

Answer 1

The ProcessModel key is only used for ASP.NET, and even then, on Windows Server 2003 it's pretty much useless because you have the Application Pool configuration.

The /3GB switch does not apply to 64-bit Windows.

As I understand it, you CAN get OutOfMemoryExceptions if you have objects pinned in memory preventing the GC from effectively defragmenting the memory stack when a collection occurs.

You should strongly consider moving your service to a 64-bit application if you know you are jamming gigabytes of data into it. IMO you're playing with fire if you are coming this close to the limit.

Answer 2

The processModel configuration element is specific to ASP.NET processes and is not applicable to other .NET processes.

If you are running a 32-bit process on a 64-bit OS, your still subject to the process limit of a 32-bit process, which is 2GB. The practical limit is actually closer to 1.5 to 1.8GB, depending on your application characteristics - in other words, its very unlikely you will ever actually reach the 2GB process barrier.

In order for your Windows service to take advantage of the full 4GB of process space your expecting you will need to:

• mark your process as LARGE_ADDRESS_AWARE. Believe this can be done using editbin.exe, but I've never done it! It also might open up a new can of worms... :) I'll see if I can't validate.
• add /3GB in boot.ini
• reboot server

Also consider the memory allocation profile of your application. If you are allocating objects greater than 85K in size, then these objects will be allocated in the large object heap. The large object heap is swept, but not compacted like other heaps, meaning that you could be experiencing fragmentation which will eventually keep the .net memory manager from allocating a continuous block of memory to satisfy the request.

You likely want to take snaps of the process and review what objects are in what heaps to get a better idea of whats going on within your process memory space.

Also, check the size of the page file on the server. An inadequately sized page file can also cause problems considering its shared across all processes, though that tends to error with system exceptions with some verbiage around 'virtual memory'.

Good luck!

Z

References:

Memory Limits for Windows Releases

Tess Ferrandez, .NET Debugging: Memory