CLR out of memory exceptions
Install ADPlus on your server (it's part of the Windows Debugging Tools). When you start observing unusually high memory usage capture a memory dump using:
adplus -hang -p <PID> -quiet -o <dump file folder path>
<PID> is the process ID of the worker process which you can get from tasklist.exe.
If you're not always around when this issue occurs then you could automate capturing a memory dump using DebugDiag:
Use DebugDiag in leak tracking mode to trigger a process dump when either your Private or Virtual memory use reaches a certain threshold. That said, I've not always found this reliable.
Use DebugDiag in Crash Mode to capture a dump whenever CLR exceptions are thrown. You can used the Advanced Settings to configure DebugDiag to produce a full memory dump upon encountering a CLR exception of type
System.OutOfMemoryException. This is more reliable and will definitely trigger. Only use Advanced Settings -> Exceptions, don't touch the Unconfigured First Chance Exceptions, leave this setting at None.
Once you have your memory dump, fire up WinDBG then load the dump file and load up SOS and start poking about.
Tess Ferrandez's blog is a great .NET debugging resource and she has plenty of articles and labs about how to track down memory leaks (these are archive.org links due to broken links):
If it is broken, fix it you should - memory issue articles
.NET Debugging Demos Lab 6:_Memory Leak
.NET Debugging Demos Lab 6:_Memory Leak - Review
.NET Debugging Demos Lab 7: Memory Leak
.NET Debugging Demos Lab 7: Memory Leak - Review
PerfMon counters are useful and can be used to confirm that you have a memory leak, but they don't tell the whole story. WinDBG and SOS are the tools you need to use to find out where your memory is being used.
Performance Monitor, aka Perfmon, is your friend - it is free and not intrusive and lightweight and can be safely run on production servers if you use less frequent sampling (every few seconds). The minimum it can do is to sample memory and CPU usage for your processes (w3wp.exe) and store them on a file.
Since you have not shared what you are doing in the application I can't suggest performance counters to store, but there are plenty in the ASP.NET and .NET and CLR.
Since you are getting a CLR out of memory exception, my hunch is GC is not working due to a pinned object or something. I doubt it is an unmanaged resource, such as bitmap, not being released although it could be.
Here are a list of counters I suggest:
.NET CLR Memory
- GC Handles
- Pinned Objects
Process for the w3wp.exe running your application
- A couple, but mostly Working Set
ASP.NET
- Managed Memory used