When close to and looking at a large field of Bamboo, frame time spikes to 300ms or more occur regularly (with frame time dependant on amount of Bamboo), lined up with memory garbage collection (the memory usage goes down corresponding to the spikes). This is even though average frame rate is still close to expected.
Not looking at the bamboo, or being 20-30+ blocks away causes frame time spikes to disappear. This was discovered with growing bamboo, fully grown bamboo does not cause these spikes. Testing with higher random tick speed (and thus higher bamboo growth speed) increases size and frequency of spikes, so the spikes are caused by bamboo growth. Spikes are also observed when harvesting bamboo from a large field of bamboo, or placing or destroying any block in close proximity to a lot of bamboo.
Conjecture: Long frame times are caused by lighting updates and block updates associated with growing large amounts of bamboo in fields, and harvesting bamboo from large fields of bamboo.
This was tested both on a multiplayer server and on a superflat single player world.
Videos (YouTube) of 50x50 field of Bamboo:
Spikes at normal random tick speed, and showing effects of proximity and facing direction
Testing 1000 and 100 random tick speed, fully grown bamboo, and harvesting
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I just tested with fast graphics, and saw nearly the same result. I have also tested on a more powerful computer. On a windows 10 computer with an i7-4790k and GTX 970 the frame times while bamboo is growing are significantly shorter, only about 50ms, and much less noticeable. Breaking bamboo still causes extremely noticeable and jarring frame time spikes on that more powerful computer of at least a few hundred ms.
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I believe this was erroneously marked as 'invalid'. This appears to actually be a duplicate of MC-123584
From the leaves looks like you have fancy graphics turned on, which means that each bamboo has to calculate transparency for each block in the 50x50 area you have, its probably too much processing light updates going through it + the block updates associated with that