[Pnet-developers] explicit calls to GC.Collect() vs letting GC take care of itself.

[Tim Nichols]

Hi -

In my application, I've found that if I explicitly induce a garbage 
collection by calling GC.Collect() periodically, the amount of memory 
used stays fairly constant (as expected).  
However, if I do not periodically force a GC and allow the GC to collect 
when it thinks it needs it, eventually I'll get an OutOfMemoryException, 
even if I set GC_max_retries = 2 in lib_gc/alloc.c.     
For example, if I call GC.Collect() periodically, I'll see about 2MB 
being used in my application.   If I let GCs happen naturally, memory 
will climb much higher than 2MB (as expected) but it will never drop the 
memory usage back to 2MB after a collection, it will be more like 
2.5MB.   I would expect it to drop it down to 2MB as in the other case.  
What ends up happeniing is that next time the GC decides to collect, the 
new floor becomes 2.75MB, then 3MB, etc until eventually it runs out of 
memory.

Why would the memory behavior be so different if I force a GC vs letting 
the GC just take care of itself?

I can't imagine it is due to a leak, otherwise the frequent calls to 
GC.Collect() wouldn't show a constant memory footprint - it would slowly 
fill up memory as well.

Thanks in advance for any insight.

- Tim