Looks like memory management on Nexus 6P has run amok on Developer Preview 4 of Android N, as many users are reporting that when all of RAM is utilized, the devices comes to freeze, and is very slow in freeing up the RAM at that moment.
Mind you, that should be instantaneous — which it is on anything other than Preview 4 of Android N. If you own a Nexus 6P, on Preview 4, then try this to reproduce the issue yourself (don’t worry, restart the device to fix it).
Open RAM-thirsty apps like games, play a video on YouTube, open 10-20 tabs of a always-fully-loaded Chinese newspaper site, and then finally touch all that up with camera with HDR+ turned on.
That should leave 0 (zero) free memory on your Nexus 6P, and that’s when it should start crawling for life, rather than freeing up the memory from unused apps and games.
To fix, simply press and hold Power button to force shutdown the device.
Right now, Google has acknowledged the issue, and is already investigating it. We’ll be sure to bring you updates on it as and when they come.
Earlier, we found a serious Wi-Fi bug on Nexus 5X with Developer Preview 4, the sent the device into endless reboot. Sure there is so much stuff to clean for Google before releasing the Developer Preview 5, or final release of Android N.