Is “Out Of Memory” A Recoverable Error?

Question

I\'ve been programming a long time, and the programs I see, when they run out of memory, attempt to clean up and exit, i.e. fail gracefully. I can\'t remember the last time

Answer 1

Yes, OOM is recoverable. As an extreme example, the Unix and Windows operating systems recover quite nicely from OOM conditions, most of the time. The applications fail, but the OS survives (assuming there is enough memory for the OS to properly start up in the first place).

I only cite this example to show that it can be done.

The problem of dealing with OOM is really dependent on your program and environment.

For example, in many cases the place where the OOM happens most likely is NOT the best place to actually recover from an OOM state.

Now, a custom allocator could possibly work as a central point within the code that can handle an OOM. The Java allocator will perform a full GC before is actually throws a OOM exception.

The more "application aware" that your allocator is, the better suited it would be as a central handler and recovery agent for OOM. Using Java again, it's allocator isn't particularly application aware.

This is where something like Java is readily frustrating. You can't override the allocator. So, while you could trap OOM exceptions in your own code, there's nothing saying that some library you're using is properly trapping, or even properly THROWING an OOM exception. It's trivial to create a class that is forever ruined by a OOM exception, as some object gets set to null and "that never happen", and it's never recoverable.

So, yes, OOM is recoverable, but it can be VERY hard, particularly in modern environments like Java and it's plethora of 3rd party libraries of various quality.