I've recently experienced high CPU and RAM usage in one of my worlds leading to stop and go mobs/player behavior due to this. This was in 1.6.4 vanilla.
I fixed it by narrowing it down to Mineshafts.dat through process of elimination, and deleting said file fixed my issues. That's when I Googled the file name and found this bug report on it. I guess this will continue to grow and need constant deletion from what other comments said, but it's at least made said world playable again.
Princess Garnet
I've recently experienced high CPU and RAM usage in one of my worlds leading to stop and go mobs/player behavior due to this. This was in 1.6.4 vanilla.
http://www.minecraftforum.net/topic/2210743-solved-164-playermob-movement-lag/
I fixed it by narrowing it down to Mineshafts.dat through process of elimination, and deleting said file fixed my issues. That's when I Googled the file name and found this bug report on it. I guess this will continue to grow and need constant deletion from what other comments said, but it's at least made said world playable again.