Ok so clearly these won't be the same for every computer.
I will describe them one by one for people that are unfamiliar with these stuff and I will put my iMac Specs after them so you can get an idea of what to do.
-Xms1024M -Xmx2048M .. This right here means what is the minimum and maximum size your launcher is allowed to use from your RAM.
-XX:PermSize=256M -XX:MaxPermSize=512M .. So this stuff here are a little advanced java stuff but in a nutshell they are what makes minecraft run a big amount of JAVA classes without a problem and are mostly useful for big modpacks. (If you have JAVA 8 ignore this line because it won't work)
-XX:ParallelGCThreads=2 .. This basically means how much processor cores you are allowing the launcher to use.
I don't recommend you changing the perm size unless you have a BEASTLY COMPUTER.
For the RAM size use the half of your RAM to be the max size and use half the max size to be your min size.
Lastly the cores you can go ahead and use the same amount of cores you have for example if you have 4 use them all its ok.
BE SURE TO NOT ALLOCATE MORE CORES/RAM THAN YOU ACTUALLY HAVE!!
For anyone who is suffering from lag spikes like I did (DID)
you can put these arguments that will significantly decrease the chance of lag spikes accruing!
Just put these in the JVM Arguments section of your launcher:
Ok so clearly these won't be the same for every computer.
I will describe them one by one for people that are unfamiliar with these stuff and I will put my iMac Specs after them so you can get an idea of what to do.
-Xms1024M -Xmx2048M .. This right here means what is the minimum and maximum size your launcher is allowed to use from your RAM.
-XX:PermSize=256M -XX:MaxPermSize=512M .. So this stuff here are a little advanced java stuff but in a nutshell they are what makes minecraft run a big amount of JAVA classes without a problem and are mostly useful for big modpacks. (If you have JAVA 8 ignore this line because it won't work)
-XX:ParallelGCThreads=2 .. This basically means how much processor cores you are allowing the launcher to use.
I don't recommend you changing the perm size unless you have a BEASTLY COMPUTER.
For the RAM size use the half of your RAM to be the max size and use half the max size to be your min size.
Lastly the cores you can go ahead and use the same amount of cores you have for example if you have 4 use them all its ok.
BE SURE TO NOT ALLOCATE MORE CORES/RAM THAN YOU ACTUALLY HAVE!!
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My iMac Specs:
Processor: 2.4 GHz Intel Core 2 Duo
RAM: 4 GB 800 MHz DDR2 SDRAM
Graphics: ATI Radeon HD 2400 XT 128 MB
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This is whats important of the computer.
This works on windows too obviously so don't ask.
Also this might not increase your FPS but believe me you will see a huge difference regarding LAG SPIKES!
Please comment below if it has been any better for you after trying this.
Note: This is tested on the original Minecraft launcher only but with +100 mods installed by a NOOB aka Me