Minecraft Forums

Hi,

my kids play minecraft on fairly basic laptops (i3 CPU) that both have 8 Gb of RAM (one is windows 7, the other windows 8.1) - but most of the RAM (> 50%) is just not used. Seems wasteful as I'm guessing the whole thing would run faster and smoother if I could coax windows into loading more of the application into this unused RAM. Any ideas?

Thanks

Doh! just found http://www.minecraftforum.net/forums/support/unmodified-minecraft-client/tutorials-and-faqs/1871637-tutorial-allocate-more-memory-for-minecraft - guess I'll start with that.

I'll give you a quick tutorial.

1. Load up the minecraft launcher.

2. In the bottom left corner of the launcher, click "edit profile".

3. Look for java arguments on the settings screen, and check it off. Then replace the current one with this:

-Xmx(number)G

[Where it says (number), insert the amount of gigabytes of ram you want it to take up. Obviously remove the parenthesis.

4. Click "save profile".

Thanks megabyte!

But, with more RAM allocation, it makes more RAM available for use, so more CPU intensive tasks run quicker.

Thanks cestislife and Jiggy (like your rig!),

my simple-minded approach was: if I can load more or all of the application into ram, then the processor accesses ram rather than the HDD in running the application (much faster access), ignoring access to system programs etc. Is this not correct? Or: is the processor still accessing application binaries off the HDD, so the key bottleneck is not being reduced? If so, maybe setting up a ramdrive to use the spare memory and installing minecraft there will have more impact?

Thanks

Most users report best performance @ 3Gb of RAM for an 8GB card.

I don't see much correlation between memory allocated and performance myself, within limits; insufficient memory causes the game to crash, not just lag or run slower, while too much also causes it to crash (I have a 32 bit OS so I can't allocate more than about 1 GB, and even that can cause out of memory errors (ironically) due to the Java process running out of memory, as it can only use up to 2 GB total, including native libraries like OpenGL; note that the crashes are different for both cases, one cause the game to lag, freeze, then close with "out of memory: Java heap space" as the cause and the other gives a "Minecraft has run out of memory" screen despite F3 showing plenty of free memory).

That said, more memory does increase the time between full garbage collections; with 768 MB allocated I see one every 30-60 minutes during normal gamplay, about twice as often but shorter in duration with 512 MB. This assumes the default garbage collector, which simply waits until used memory hits 100% before running; the default JVM arguments in the launcher enable an incremental GC, which causes stuttering when it runs which is much more objectionable than a 1/2-1 second pause. Note that in any case the GC has to eventually match the rate at which the game is allocating new objects, so allocating a huge amount of memory can forestall this but not indefinitely, and as mentioned it takes longer to go through more memory.

It is important to allocate more memory though if you use higher render distances (the game already only lets you go up to 16 chunks in vanilla unless you allocate 2 GB; I say vanilla since Optifine lets you get around this); the memory usage roughly goes up by the square of the render distance since most of the memory the game uses is used to store chunks.

Remember also to leave plenty of free system memory; with 768 MB allocated (all at once as I use -Xms768M) the Java process uses around 1.3-1.4 GB of memory, leaving about 1 GB free (out of 3 GB total); this free memory is used by Windows (and most other OSs) as a disk cache, which can speed up chunk loading after the files are first loaded (chunk loading when moving into new areas is mostly dependent on how fast your CPU is).

-Xmn means Java allocates an EXTRA 768mb for the young generation. -Xms is the beginning allocation state, and -Xmx is the total memory available for allocation. Since you are running a 32 bit OS, TheMasterCaver, Java GC is different. For a 64bit version of WIndows 8.1, I see GC every 20-30 minutes. Just sharing a tidbit of information.

Xmn does not allocate EXTRA anything. this controls the size of the subset of the heap used for the new generation. So the max heap size (Xmx) minus the new gen size (Xmn) tells you how much space you have for oldgen