The check to find dirty itemstacks and send update packets each tick can be very intensive as it checks the entire itemstack, including the entire NBT map. To save on this, 19/20 times we will simply compare the basic count/data/type. If for some strange reason the NBT of an item already existing in an inventory is changes, it will take up to 1 second to show, with an average time of half a second. This odd 0.5 second delay is far preferable to lag every tick, and shouldn't be noticed by anyone.
This patch adds world configuration options for max-tick-time.entity / max-tick-time.tile which allows setting a hard cap on the amount of time (in milliseconds) that a tick can consume. The default values of 50ms each are very conservative and mean this feature will not activate until the server is well below 15tps (minimum). Values of 20ms each have been reported to provide a good performance increase, however I personally think 25ms for entities and 10-15ms for tiles would give even more significant gains, assuming that these things are not a large priority on your server.
For tiles there is very little tradeoff for this option, as tile ticks are based on wall time for most things, however for entities setting this option too low could lead to jerkiness / lag. The gain however is a faster and more responsive server to other actions such as blocks, chat, combat etc.
This feature was commisioned by Chunkr.
This was useful when plugins first started upgrading to uuid because each
plugin would implement their own way for grabbing uuid's from mojang. Because
none of them shared the result they would quickly hit the limits on the api
causing the conversion to either fail or pause for long periods of time. The
global api cache was a (very hacky) way to force all plugins to share a cache
but caused a few issues with plugins that expected a full implementation of
the HTTPURLConnection. Due to the fact that most servers/plugins have updated
now it seems to be a good time to remove this as its usefulness mostly has
expired.
Thinkofdeath