Minecraft Forums

Quote from Mc_Destroyer4»

There are alot of things that could be different, but try:
1.Make sure you entered your 12gb xmx right
2. uncheck your java custom and run as if you never touched it
3.Maybe your video setting got changed, check them
4. You very well Could have never had 200fps and you minecraft was glitching, and setting you java xmx fixed the glitch

Also you ever actually said if you noticed the change while playing as in the game was lagging or if you just saw the number
Hope this helps!!!
Mc

Quote from sensi277»

On the topic of RAM usage, you should only ever allocate 350-512 MB to Minecraft, as it never really needs more than that (unless you're using an excessive amount of mods). Use more than that, and the other programs on your computer (including Windows itself) run really slowly. The reason behind this is that when Windows has free memory, it fills that memory up with a cache containing some commonly accessed files or programs. It does this so that if you launch Google Chrome, that program is (at least partially) already in memory. It doesn't have to go to the hard drive to access it, as it's already right there in memory. But when you use up more memory, the cache gets smaller, and eventually disappears if there isn't enough room. At this point, the processes running in the background are already using up all the memory. So what happens when the amount of available RAM goes down still? What happens is that Windows takes the programs that are doing the least stuff, suspends them and puts those processes into a "page file". A page file is essentially a file that Windows puts suspended processes in when there isn't enough RAM to keep them running. The programs sit there on the Hard Drive while your computer is doing other stuff, and when the processes are needed, it just loads them back into RAM. The reason it does this is because processes have to be in RAM to be able to function. Anyways, Windows wants to put the process back into RAM, but it has a problem. There isn't enough spare RAM to copy the process to. So what Windows does is it takes another program that isn't doing very much, suspends it, and puts it in the page file. It can now put the original process back into RAM.

This whole process takes a relatively long time for the computer to execute, simply because hard drives are really slow. It takes time to write a process to the hard drive, then to read it and erase it from the hard drive, especially when RAM is low and it the computer has to do this many times a second. Meanwhile, Minecraft is running, and it's suffering performance issues because the computer is constantly reading and writing to the disk. This wouldn't be happening, though, if Minecraft hadn't took so much memory for itself. Even if Minecraft isn't actually using much of that memory, no other processes can use it because it belongs to Minecraft.



TL;DR: Only allocate about 350MB-512MB to Minecraft, or your performance will likely suffer.