Server CPU issues 1.15.2

Ryu Yamato

New Member
Apr 14, 2020
Hello! notably been working on a server and as the title states, the CPU spikes to 100% when 2 or more players are active, and it seems this happen as of recent, and notably doesn't seem to be plug-ins. Any recommended Fixes?


BeastNode Staff
Dec 18, 2015
The Realm of Obscurity.
Your servers performance issues will be down to the server software itself - Minecraft 1.15.2 is not stable and will have a much higher chance for performance issues than older server versions. Unfortunately the Minecraft 1.15 update did not do much to resolve the major causes of serverside lag introduced in the 1.14 update (and to some extent the 1.13 update).

The Vanilla 1.14 release brought with it as many performance issues as it did new features - particularly serverside, on top of the already present performance issues from the 1.13 release (mostly chunk loading/generation related).
1.14.1/1.14.2/1.14.3 did not improve on this much if at all as very few serverside issues were touched on in these releases, and while 1.14.4 did attempt fixes for a number of serverside performance issue causes it was still not considered "Stable" when compared to older MC versions (the last "Stable" Vanilla release is still considered to be 1.12.2 at this time).

While the 1.15 update was stated to primarily be a performance fixing release the vast majority (almost all) of the issues resolved in the update are clientside, not serverside.

The issues in 1.14.4 with the Pillager AI have had fixes applied (though reports on how much this has improved the issue are lacking so we are not sure just how much this has helped with Pillager-based lag) however the main central cause of serverside lag issues going back to 1.13 (and made considerably worse in the 1.14 update) is chunk loading/generation which has had little to no work done on it in the 1.15 update.
Chunk rendering has had a major overhaul but this is entirely clientside, it has no effect on the serverside aspects of chunk loading/generation.

At this time all we can suggest to try and help with general server performance is the same as we have been suggesting for 1.14.* issues:
- Lower the view distance in the (Files > Config Files > Server Settings on the control panel) to 5 or 6, save changes and restart the server to lower how many chunks will load in around players on the server which will help with the CPU usage spikes.
- Avoid loading in a lot of chunks (new or pre-generated) by flying around or travelling long distances by boat/horse/cart etc...
- Make sure to restart the server regularly (recommended at least once a day) to unload excess chunks and entities and refresh the RAM usage.
- Avoiding the usual potential lag causes such as mob build ups/grinders or large amounts of active redstone etc.. is also recommended.

Avoiding Jungle biomes may also still be helpful, as may avoiding leaving leaves to decay. There were numerous lag issues in 1.14.4 that were related to leaf decay and Jungle biomes in particular and currently we are unsure if these have had adequate fixes in 1.15.

I assume as you mentioned plugins that you're already using Spigot or PaperSpigot, which would also be a recommendation as Vanilla is not recommended for use at all at this point.

When using Spigot/PaperSpigot it must also be updated regularly to keep up to date with any patches/bug fixes they have issued - to do so simply log into your server files and delete the jar folder before restarting the server (recommended to do at least once a week).

There is also a guide here on some optimisations you can make through the bukkit.yml, spigot.yml and paper.yml files to help with general server performance (while the guide is for 1.14.4 servers it should be fine for 1.15 as well):⚡.283181/

If you're using Spigot, not PaperSpigot, and it still performs poorly with the bukkit/spigot.yml files tweaked as stated in the guide then using PaperSpigot and doing the paper.yml tweaks in the guide would be advised.

Unfortunately beyond this there is little we can suggest for 1.15 server issues - the server version/software itself is simply full of performance issues that would require serverside fixes on Mojangs end to improve (as Spigot/Paper can only do so much when the Vanilla software itself has poor performance).
Unfortunately at this point it also seems like 1.16 will have similar issues - not much has been mentioned in the 1.16 snapshots that would indicate any real fixes for the chunk loading/generation lag issues. There have been some fixes for other possible server lag issues, such as mob AI, but as chunk loading/generation is one of the main/biggest issues with server performance drops right now without this being fixed/tackled properly the issues will likely persists over into 1.16 as well.