How to predict Out of memory?

Question

In my C# program I do various memory-consuming operations. Depending on the amount of memory currently available and various non-constant circumstances, the program fails with OutOfMemoryException at different stages.

I would like to stop processing at some point when it is more or less obvious that the program will fail with an OOM in the near future.

However, there is no fixed threshold for this; Other users may have more (or less) memory, another OS with its memory specifics and so on.

I do not want to just check that the software consumes more than eg 500MB as this may be too high or too low a restriction.

Is there any reliable way to predict an upcoming OOM in .NET?

Answer 1

The sort answer is that its probably not the best solution - instead of anticipating when you are going to run out of memory and trying to do something about it, you should probably either try and reduce the memory consumption of your application or just wait until the OutOfMemoryException exception is thrown and then clean up.

An out of memory exception is thrown whenever the .Net runtime fails to allocate the memory that was just requested - this could be because the machine has run out of physical memory and the swap file is disabled (or the machine has run out of disk space), or it could be because the virtual memory space of the process is too fragmented to allocate the desired block of memory (which can happen when working with large objects). Predicting when this is going to be is fairly difficult.

You can use the MemoryFailPoint class to check to see if a certain amount of memory is going to be available before starting an operation that uses up a large amount of memory, however this class does not guarantee that the memory will remain available for the duration of the operation and so your application could still fail with an OOM exception anyway. Although this class can be useful in some scenarios to attempt to reduce OOM exceptions (and in turn to avoid corrupting application state), its probably not going to be a "magic bullet" solution to your problem.

Answer 2

Many of the OOM exceptions I observe so far were caused by improper written application with memory leak or third party components. Consider using a data structure optimized for your operation.

Detecting OOM is quite difficult because there are randomly thrown. Maybe you can use MemoryFailPoint and Performance counters (available memory) to ensure there is enough available memory.

Answer 3

MemoryFailPoint should do what you want.

http://msdn.microsoft.com/en-us/library/system.runtime.memoryfailpoint.aspx