Decreasing performance

[dudi]

Hi,
I created an application that retrieves the images from the viewfinder one after another. When running the application I calculate the frames per second (fps) that I am able to retrieve from the viewfinder. At first I get 13-15 fps and slowly it decreases to 10-12 fps and eventually stays on 8 fps (it eventually stays on 8 fps after 5 minutes or so). Is there a possiblity that my process's priority is decreased? Or else how can this decrease in fps can be explained? I know that there should be a runtime optimizer such as JIT or similar, but that should cause better fps as time passes, no?
I don't instantiate any new objects and don't have any memory leaks during the running of the applications. I've checked this in the emulator and everything looks ok.
Any suggestions?

[hartti]

Was the decreasing performance noticed on real phones or on the emulator? Which phone?

Without any more information my guess is that memory is getting low. (yes, I read your message and the memory comment also :-)

Hartti

[dudi]

It's N95 and N73. How can the memory get low? I don't allocate anything during runtime

[ehudshapira]

Check what freeMemory() says and try seeing if manually running gc() matters.
I think I encountered in the past an API method (it was RMS related) that had a memory leak. Maybe that's what happens in this case.

[hartti]

How could the system running low on memory?
You are reading images from the camera in quick succession. It could be possible that even though there is no "memory leak" the system / garbage collector does not have time to fully release the memory. At some point the system has to allocate some time for the garbage collector to release the memory and hence the fps is slowed down. Did I make any sense (all this is of course pure guesswork without exactly knowing what your MIDlet does etc.)

Hartti

[dudi]

Just to update this thread (for future developers who encounter this sort of problem). I've done some more testing using the WTK profilter and indeed the JVM does instantiate new objects, for example when drawing a string on the screen a String object and string buffer are created. To solve the problem (more precisely to make it worse than it is), I'm calling the garbage collector once every few seconds to prevent the automatic garbage collection that takes too long when the memory is too full.

Thanks again to Ehud and Hartii