memory leak in 1.8 snapshot

while doing anything, in f3 you can see the memory rapidly going up, usually to about 25%-30% or around 1500mb, then it suddenly drops to 4% and i get a huge lag spike every time it drops. it usually goes up from 4 to 30 in around 20 seconds and then drops back down. every time it goes through the loop it tends to get to a higher percentage each time. when i first start it goes to 25, then 27 then 29 etc until it levels off at about 40% each time before it drops down back to 4%, cause the game to suddenly stop for a second then continue. this happens in all 1.8 snapshots