There have been some reports of a suspected memory leak in Aperture, see this thread: Is there a memory leak in Aperture 3.5?
But have you tried the usual trouble shooting - repaired the permissions and he library, reinsatlled Aperture, just in case the download was currupted?
Downgrading requires to have full, working backups of your system and your Aperture library from before the upgrade, so you can restore everything from your backups. You can neither downgrade the library nor the system by reinstalling 10.8.5 on top of 10.9.
Finding out, what is causing the memory problem requires requires a bit of diagnosis - it is not necessarily an Aperture bug. It might be caused by images or videos that cannot be processed, incompatible plug-ins or other software, hardware problems, system trouble.
I'd try to keep the Console open, when Aperture is running, to see disgnostic messages.
Also work with a new Aperture library for a while, to see, if the library is causing the problem. Try to remember, what your most recently installed applications and utilities were.
How is your Aperture drive connected? Directly or using a HUB?
Exactly my problem ( well one of my Aperture problems)! I have a little utility running called MemoryFreer which frees upINACTIVE memory. Only need to activate it when Aperture is open. However if I don't catch it soon enough the whole machine (MBP retina) locks up and has to be hard reset with the power button. I then have to repair the damaged Aperture library beofre I can use it again. This happens with any of my many Aperture libraries.
Come on Apple. You know about this issue. Please fix it.... and soon! Lightroom is beginning to look very inviting.
I am glad I am not the only one. Since the last comment / plea for help the problem still persists. It eased a little by buying an extra 8gb of memory to make 16gb and reinstalling both aperture and sox mavericks this was done under guidance of apple. But still the mac runs at 15.98gb of memory used or occasionally over 16. This can not be correct, any more ideas?
Part of changing to a mac was to avoid this memory hungry application.
One other featur the application qtkitserver (some 3 or 4 digit number) not responding usually appears as the memory used steadily increases.
It looks like I am also going to have to give up on aperture and swap to Lightroom.
Ap hasn't always had this issue but 3.0 was not a good upgrade. It's never really worked so well since.
It seems it also is crashing itself and the Mac through its determination to reprocess 18000 thumbnails. No idea why. Nothing wrong with the ones I have now but it is constantly chuntering through taking resources away from the work that I myself I would like to do. Even if I cancel or pause this operation, it starts it again very soon.
I did ask a few weeks ago about my memory loss, and sad/glad to see it's not just me.
"Since going to Mavericks and Aperture 3.5, I keep getting the alert that I've run out of memory.
I never had this issue at all before, and was wondering does 3.5 use a lot more memory, is it a common issue or a fault on my system.
I have a 2009 2.8 iMac with 12GB ram and not that keen on spending £70 just for another 4GB ram."
I agree whole-heartedly with you Mark. Everyone is having this problem, everyone. As a professional photographer, this is becoming unacceptable. It's clearly a memory leak and not of our making.
Apple, please fix. How many comments to you need to realise there really is a problem here and not with your users machines. I'm using a hi-end macbook pro with 16gig memory and never had a problem before. In truth, since installing Mavericks, my system generally freezes a lot with memory loss so it's not just an Aperture problem therefore I'm not even sure that Lightroom would be any better. Mail freezes a lot to and there are many many comments on that subject too.