I’m trying to find the source of a memory leak in a Compact Framework application using the Remote Performance Monitor. I managed to remove a few minor ones related to brushes and other graphic objects, but I still don’t have a clear idea of what is causing the main problem.
At this point the only objects that seem to never go back to their original count are System.String objects. I find this to be very weird, since I would’ve thought that in order for these objects to remain uncollected, the objects that contain them would have to remain as well, and yet no other type of objects seem to be increasing along with the System.Strings.
I’m trying to find out which new String objects are the ones that remain after the application returns to its original state (i.e. the login screen). The problem is that originally, the application loads with about 2200 string objects, and then after process “X” it increases another 70 or so which never get collected. I don’t know how to identify those 70 new objects, in order to find out who is holding on to them and make the appropriate corrections.
Does anyone have any experience in which Strings were not being collected? Is there any way to separate the new objects created during process “X” from those that were originally required by the application so that I can know which are leaking? Any advice would be appreciated.
Thanks
**UPDATE
Ok… there is something very strange going on. I’m starting to doubt whether there is a leak at all.
Let’s say that I take a memory snapshot at the Login screen which is the original starting point of the application. Imagine that there are 1000 string objects in memory at this point. Now, if I login and choose an option from the menu, I’ll take a snapshot once the new screen is loaded. Let’s say that loading this form increases the string count by say 50 objects. When I logout and take a snapshot again at the login screen, only 25 of those objects have been collected, the rest will stay in memory from then on.
The strange thing is that if I keep repeating this process, no further string objects will accumulate. Instead of the string count increasing by 50, only 25 will be added at this point, and those same 25 will be collected once I go back to the login screen. I’m thinking that if this were an actual leak, then each time that I opened that screen the string count would increase permanently by 25, but this only happens the first time.
This happens to me on every new screen that I open. At first there is a small permanent increase in the overall string count, but once I’ve loaded that particular screen, any increase in the string count during its execution will be collected once I go back to the login screen.
All of this has led me to believe that perhaps those strings are part of the inner workings of the CLR or something like that. Could it be some sort of caching done by the runtime? Perhaps it is storing my string constants for faster loading? Something like that? I hope this wasn’t too confusing.
if you’re using CF 3.5, then use the CLR Profiler instead of RPM. It will show you all objects and the roots that spawned them. It would allow you to walk back the root tree to figure out where they were allocated.
EDIT
So you’re saying that you aren’t actually getting OOMs or any aberrent behavior? Sounds like you’re trying to optimise when it’s not necessary. Those string are likely things like Form captions, etc. that the JITter is creating and would get collected if/when the objects get collected. What they are, though, really isn’t terribly important if you’re not actually seeing memory problems.