Massive Mountain Lion memory leak
I will start describing the problem where I first discovered it.
My early 2011 MBP had been asleep, and upon opening and waking it, it was incredibly slow. I opened activity monitor and couldn't believe my eyes.
I have 8 GB of RAM, and all but 8 mb was in use. Around 6 GB was "inactive". I had no applications running besides Activity Monitor.
I opened terminal and ran the purge command After a short wait, total memory usage was back to around 2 GB. Then right before my eyes, over approximately 30 seconds, the "inactive" memory grew until once again, I had about 8 mb of RAM free. This fluctuated a few mb, but nothing significant.
After rebooting, I opened Activity monitor again, to watch ram usage. Usage increased to a little more than 2 GB. I then launched the App Store. Before putting my laptop to sleep earlier, I had been downloading a 10 GB update to Borderlands, but had paused the download, and quit the application before closing the laptop. I hit resume download, and went back to Activity Monitor. Memory usage seemed normal for several seconds, but shortly started increasing rapidly again. I imediately hit "pause download" in the App Store. But ram usage continued rising, so I quit the application. It kept rising, until my full 8 GB was in use.
At this point I took a screenshot:
The only thing I have left to tell you is that before upgrading to ML, I had previously attempted to download the same update, but hadn't had time to download the full 10 GB, so had cancelled the update. That was in Lion 10.7.4, with 4 GB of RAM, and I had no issues.
MacBook Pro, OS X Mountain Lion (10.8.2)