The bug
When particles of some not-full-blocks (list below) are created the game gets a lag spike for a few seconds. The lag is more and more noticeable the more and more the not-full-block that created the particles has other not-full-blocks nearby.
I can't exactly understand which blocks are affected by the lag, but these are the ones I found: chest, trapped chest, hopper, anvil, brewing stand, cauldron, piston and sticky piston head, extended piston and sticky piston (but not not-extended pistons), end portal, end chest.
How to reproduce
(optional: open Alt
+ Shift
+ F3
)
Place a chest with other adjacents chests to create a star-shape (
)
Jump on the middle chest from 30 blocks above (
)
As I said the lag comes even with a single tile entity, but it might be necessary to openAlt
+Shift
+F3
and look at the fps-graphic to notice it.
Also affects end portal particles.