TickMender

TickMender is the fix and performance mod of the Nytheria modpack (Fabric, Minecraft 1.21.1, about 415 mods). It holds 37 small repairs for crashes, lost data, memory leaks, lag and slow starts in the game and in other mods, for cases where upstream has no fix.

Every repair has its own switch, stays idle when its target mod (or the exact version it was written for) is not installed, and returns what the original code returns: the same world, the same gameplay, the same picture.

What it is, and what it is not

• It was built for Nytheria's mod set. Most fixes target one named mod, often one exact version, and do nothing anywhere else.
• A few fixes are for the game itself, for Fabric API or for PuzzlesLib. Those are active in any pack that has the target (see Compatibility).
• It is not a general optimiser like Sodium or Lithium, and it does not replace them.
• It changes no gameplay rule: no spawn rates, no mob caps, no tick rules, no view or simulation distance. It does not change world generation or visuals.
• The numbers below were measured with Nytheria on one PC. They are not a promise for another pack.

What it fixes

The name in the first column is the fix's switch in config/tickmender.json.

Crashes and lost data

Memory leaks at world close

A closed singleplayer world, or a stopped server, used to stay in memory for the rest of the game run: about 235 MB per world opened and closed. Five fixes let it go.

Server tick

World generation (flying over new terrain)

Client frame time

Start-up, world load and resource reload

Log filter

logFilter keeps known, harmless WARN and ERROR lines of other mods out of the log, so real problems are easier to see. It only looks at the message text of WARN and ERROR lines. The 57 patterns are in config/tickmender-logfilter.json, you can edit them, and every pattern has a hit counter. A summary of the hits is written when a server has stopped, when a world was left and when the client exits.

The pattern list was written for Nytheria. In another pack, read the list before you rely on the log, or switch logFilter off.

JVM arguments hint

jvmArgumentsHint (client) is not a code fix. A player who starts the game without the recommended JVM arguments is shown them once on the title screen, with the place to paste them, a Copy button, Done and Do not show again. The mod only shows the line. It never changes launcher settings and never writes into the launcher's files, and the line never contains -Xmx or -Xms.

Measured results

Measured on the pack author's PC (Intel i5-14600KF, 64 GB RAM, RX 9070 XT) with Nytheria, Java 21 and a 10 GB heap. Most cells are one run, on a PC that was not idle, so treat differences below about 10 % as noise.

Dedicated server, with and without TickMender

Same server, same conditions: four simulated players, simulation and view distance 10, 10 GB heap. The only difference is the TickMender jar. These runs used an earlier build with 15 of the 37 fixes (all ten server tick fixes among them).

The largest single effect is PuzzlesLib's event dispatch: 7.6 ms per tick before and 0.2 ms after with players standing, 13.1 ms and 0.7 ms while they explore. Part of the gain with standing players is the state of the run (mob caps, a data pack clock), not the fixes.

Client

Shaders on, render distance 12, 10 GB heap, singleplayer.

"The whole pass" means: the pack before the performance pass against the pack after it. That is TickMender together with fixes in two other mods of the same author (BetterX Remastered 30.5.1 and Sporran 1.0.4) and a few config changes in the pack. Those numbers are not TickMender's alone.

The JVM arguments hint

The same flight, the same average frame rate, 10 GB heap. Only the JVM arguments differ.

How you can trust it

• One switch per fix. Set it to false and restart: the fix's mixins are not applied at all and the target runs its own unmodified code.
• Idle when there is nothing to repair. A fix does nothing when its target mod is missing. Ten fixes are written for one exact version and do nothing with any other.
• It says what it does. One log line at start-up lists the state of every fix: active, idle (...), off (config) or inactive (...). Every injector is checked after it was applied, a missing one is named in a warning, and the original code runs unchanged at that point. The first use of every fix is logged once.
• Verify mode. With -Dtickmender.verifyCaches=true, every fix that answers from something it remembered, or with code of its own in place of a mod's, runs the original code as well, uses the original's answer and reports any difference (VERIFY FAILED) and a count (VERIFY RESULT).
• 372 unit tests in the build of 1.0.0.

In the last verify runs before the release, eleven fast paths were compared with the original code in the running game. No mismatch.

Candidates that would have changed what the game does, or could not be shown to keep it, were left out on purpose.

Configuration

config/tickmender.json is created with defaults the first time the mod starts. It holds one line per fix:

{
  "puzzlesLibDispatchCache": true,
  "ringPlacementExecutor": true,
  "irisSameDimensionReload": false,
  "logFilter": true,
  "jvmArgumentsHint": true
}

(Shortened. The real file has all 37 switches.)

• true is active, false is off. The file is read once at game start, so restart after a change.
• After an update that brings new fixes, their switches are added with their defaults. Everything already in the file is kept.
• A value that is not true or false, or a file that is not valid JSON, costs one warning in the log and falls back to the default. The mod leaves your file untouched.
• config/tickmender-logfilter.json holds the patterns of the log filter.
• A file tickmender-jvm-presets.json in config/ replaces the built-in line of the JVM arguments hint. -Dtickmender.jvmHint=off disables the hint for one start.

Compatibility

• Minecraft 1.21.1, Fabric Loader 0.16.0 or newer, Java 21.
• No other dependency. Fabric API is not required. Nothing is shaded.
• Works on a client, on a dedicated server, or on both. Neither side needs the other to have it. It adds no packets and no registries.
• The client-only fixes are idle on a dedicated server.

Where the fixes apply:

• The game itself (any pack): ringPlacementExecutor, merchantShutdownSave, structurePlaceFilter, structureTemplateCacheHit, stoppedServerCriteria, stoppedServerBiomeSearchCache, zipPackListingIndex, blockStateModelIdMemo. How much they do in another pack was not measured.
• Fabric API 0.116.17: fuelRegistryApplyOnce, stoppedServerFakePlayers, closedWorldRenderContext.
• PuzzlesLib 21.1.x: puzzlesLibDispatchCache, for every pack with mods that use PuzzlesLib.
• Not tied to a mod, on by default: logFilter and jvmArgumentsHint. Both were written for Nytheria. In another pack, check the pattern list and the recommended line, or switch them off.
• Everything else: one named mod each, as listed above. A fix whose target looks different from the version it was written for is not applied, and the log says so.

FAQ

Does it work outside Nytheria?

Yes, it starts in any Fabric 1.21.1 pack. What it does there depends on which target mods and versions you have. The start-up log line shows which fixes are active. Expect a fraction of the 37, and do not expect Nytheria's numbers.

Can I add it to, or remove it from, an existing world?

Yes. It adds no blocks, items, registries or packets, so a world does not depend on it. What stays behind after removal are its files: config/tickmender.json, config/tickmender-logfilter.json, the folder .cache/tickmender/ and tickmender-jvm-arguments.txt.

Does it change gameplay?

No. No spawn rate, cap, distance or tick rule is touched, and the performance fixes return what the original code returns. The four fixes for crashes and lost data change one thing on purpose: the data is no longer lost. One example: a wandering trader that nobody has opened is saved without trades at a server stop and rolls them at its first use after the restart, with the game's own roll.

Do players need it to join a server that has it?

No. And a client that has it can join a server that does not.

What does the JVM arguments hint do?

It checks which arguments the game's Java was started with. If the recommended garbage collector settings are missing, it shows them once on the title screen, with the steps (those of the CurseForge app when the game was started by it) and a Copy button. You paste the line yourself. If the game runs worse with it, remove it again. There is no hint when the arguments are already set, when you chose another garbage collector, with less than 7 000 MB of heap, or after "Do not show again". Switch: jvmArgumentsHint.

Why does the log say a fix is idle?

Because there is nothing for it to repair: the target mod is not installed, the installed version is not the one the fix was written for, or it is a client fix on a dedicated server. inactive is different: the target is there but looks different, a warning names what is wrong, and the original code runs unchanged.

Licence and credits

MIT. Free to include in any modpack, no permission needed.

Written by Navrelis for the Nytheria modpack. TickMender is not affiliated with the mods it repairs and contains none of their code. If a mod you use is repaired here, the right place for the real fix is still that mod.