If you stick to managed code and standard coding (nothing that does unconventional things withe CLR) in .NET, is there any reason to manually invoke the GC or request to run finalizers on unreferenced objects?
The reason I ask is thaty I have an app that grows huge in Working Memory set. I'm wondering if calling
System.GC.Collect();
and
System.GC.RunFinalizers();
would help, and if it would force anything that wouldn't be done by the CLR normally anyways.
No, it won't help. Don't do it. The CLR already handles all the memory management-related stuff in a fine way, and no explicit call will do something it's not already doing.
Try to look for memory leaks in your program: while .NET languages are memory-managed, it doesn't mean it always knows when you're not using a certain object anymore. For instance, objects attached as event listeners to other objects are considered rooted by the GC and won't be collected.
You can try SOS to seek leaks.
If there is really no leak, then your program truly needs the memory it has.
Yes, it's useful for writing unit tests that require certain Dispose/Finalize methods to be called deterministically (as seen from the view of your test) for example.
Of course there's a reason, they wouldn't have provided the Collect() method otherwise. They are few and far between though. Only ever use it when you know that a whole bunch of long-lived objects that would have been promoted to gen #2 are ready to be collected. Or to release a COM object that has lots of references that you cannot possibly track should really be unloaded. Or to work around crummy code that doesn't call Dispose() when it should.
It's rare.
Leave it to CLR. Use some tools to identify the issue that you have mentioned.
@zneak : Actually, this isn't entirely true. I ran into a situation in which I was intermittently and non-deterministically running out of memory while running through a large set of data (that involved a lot of creating and destroying managed objects) in c#.
Manually invoking garbage collection once per loop fixed it. However, this is rare, and in most cases leaving the garbage collector to itself is the best course, however, I wouldn't make a blanket statement that one should never manually invoke GC as that is simply incorrect.
Also, System.GC.Collect(); is useful when you want to measure memory consumption by some containers. For example, you have Database store and service which cached indexed pieces of data, which a loaded sequentially and synchronously. When your service is under memory pressure it can unload large pieces of least recently used data.