Opis

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Opis is a powerful tool made by ProfMobius to track down lag induced by entities or Tile Entities. You can download it here if you don't have it in your mod folder already. By default Opis comes preinstalled on current versions of GTNH.

Opis Interface

Summon the Opis window with the following command:

• /opis

Summary Tab

This is the default tab. On this tab you can see various information, such as the tick time overall, network data between the client and server (upload rate, download rate, ping, ...) as well as the amount of forced chunks and loaded chunks. To trigger a profiling session, click on the button named "Run Opis". A progress bar will display under the button which changes to "Running..." while a profile is generating.

Generating a profile is very taxing on the server and lag should be expected during the process. Once profiling is finished, the game window will freeze, taking some time for the game to process all the data. Once it's done data will populate to the other tabs. Use the Tracking tab or Server timing tab to learn more about lag on the server.

Ping time as used by Opis includes not only packet travel time between the client and server but also the processing time of that packet at the server. For example, a high ping time might correlate with a delay between breaking a block client-side, and having that block actually be removed from the game world and drop as an item. Ping is also graphed at the bottom of the Summary tab in real time.

Forced Chunks are chunkloaded chunks, usually by an item such as a Railcraft Anchor or mod like FTB Utilities. Loaded Chunks are all chunks currently active in memory.

Tracking Tab

In the tracking tab, you will be able to see in real time various data once you'll have initialised a run. They will be sorted in 4 categories:

• Players tab
• Entities tab
• Tile Entities tab
• Dimensions tab

Players tab

In this tab, you'll see all the players online, the dimension they are in, as well as their coordinates in the dimension. You can also teleport yourself to them or pull them to you.

Entities tab

In this tab, you'll be able to see the loaded entities, and you'll also be able to kill them all. Be careful with this option, this can cause unintended side effects for the players, like losing their nametagged mobs.

Tile Entities tab

In this tab, you'll be able to see how many tile entities there are in your world loaded for each type of tile entity.

Dimensions tab

In this tab, you'll be able to see the load caused by entities and tile entities in each dim. It should be noted that it's only entities and tile entities load, not the total load by dimension (for instance, AE2 can do some additional load that Opis cannot see). The purge buttons will ask you to trash any mob in the dimension, any item on the ground, as well as purging chunks to only let force loaded chunks. Keep in mind that it's not a proper way of unloading a chunk, so you may cause unintended behaviors sometimes by doing this. In the screenshot below, you can see that an empty dim is taking some load even if the dim is not loaded, this is why it is recommanded for public or semi-public servers to limit the amount of personal dims, as the cumulated load is not neglectible.