I did know if this was covered in this topic so I wanted to post here if anyone is having this issue with Mantle.
update.
I may experienced memory leak and performance degradation in BF4 MP on a 64player Siege of Sanghai map 2500 tickets using Mantle. At some point the game started behaving strangely, unfortunately i didnt have fps and drawgraph enabled to see what was happening. Ill try again in the same map and see if it will happen again.
On large/long maps it's more noticeable as the leak creeps towards your RAM ceiling. You get lag, spikes and a out of memory error. I don't think the issue was fixed in the last BF4 patch nor 14.9 driver but I can't test it myself. I'm going off of what I've read on forums.
If you want to test it yourself, you can try Hardware Monitor. It's what I use for memory watching, however I have two monitors. I don't know of an overlay program that will let you watch your RAM in game.
On the BF4 side of things, the problem has been diagnosed unofficially. *"The fix is to go to the Battlefield 4 folder and locate a file called "WeaponChunks.sb" inside /Data/Win32/ folder and delete/rename/move it. "
That has worked for me, however, you do lose some of the audio from weapons. There haven't been any issues with gameplay by removing/renaming the file above. It will increase your FPS, smooth out your FPS and stop the memory leak.
*Source:
http://cte.battlelog.com/bf4/forum/threadview/2985968005281976156/last/post_2985968005414880988