So, i`v been playing minecraft for several years wondering why it was running soooooo slow. my friend had a laptop with the same amount of ram as me, 8 GB of it. his minecraft always loaded faster, ran faster, and got much, much better fps without optifine! i was forced to use optifine to get decent fps, but then i could not play with mods! so, i did a bit of research on my pc, and i found out that my graphics card was steeling ram from my computer, therefor making minecraft run a lot slower. so, all i had to do was this:

step 1: open the minecraft launcher
step 2: click edit profile
step 3: check resolution
step 4: change the resolution to 640 X 480
step 5: scroll down and check: jvm arguments
step 6: put this in the box instead of what is already in there: -Xmx3G (the 3 is how much ram you allow minecraft to use.)
note: you may want to change that number to something lower, or higher depending on how much ram your PC has. look online on where to find how much ram your PC has.

i hoped this helped you, as it helped me.
by!!