1.20.4 Summary of Patches
Attempts to prevent chunk system deadlocks or provide additional debug information in the log when they occur. These deadlocks usually manifest as the server freezing indefinitely (e.g. entities not moving), while the client continues to work just fine.
The patches in this group fix concurrency-related issues within Minecraft and/or Forge. Most of them result in rare, hard-to-diagnose crashes during loading.
Fixes a memory leak in vanilla caused by the ender dragon retaining a reference to the previous client world.
Fixes Forge configs occasionally becoming corrupted when launching the game.
Experimental, not enabled by default. An attempted fix for the memory leak issue that occurs after playing long enough on 1.16.
1.18 and newer. A key optimization. Ports a patch from Paper that fixes issues on 1.17 with chunkloading requiring huge amounts of memory and generating many CompletableFuture instances. 1.18+ are now able to load worlds on only 400MB of memory like 1.16 could.
Reduces the memory usage of old client-side worlds that aren't needed after switching dimensions. These are normally garbage collected in vanilla, but mods sometimes retain references to them.
Core patches required for ModernFix to work
Patches used when running in a development environment, for speed improvement and/or testing
Adds ModernFix to the branding list on the title screen, and also to the F3 screen.
Normally off, can be enabled to force the raw stack trace to be dumped to the log when a crash occurs. Occasionally vanilla's crash report system fails to work properly and gives an entirely irrelevant stack trace/report.
Remove the Unicode font, saves 10MB but causes special characters to no longer render
Adds the vanilla watchdog to singleplayer worlds as well, but just prints out the stacktraces rather than forcefully terminating the world. This version includes the functionality of Fullstack Watchdog, but the latter is still needed for multiplayer.
Uses a couple injections to measure world load time, datapack reload time, resource reload time, bootstrap time, and adds the necessary hooks to enable vanilla's unused profiler logic for resource reloading if so configured.
Adds easter egg features (does not affect any vanilla visuals or behavior) when running on a snapshot version.
To be used for debugging purposes only. Causes a thread dump to be output to the log every 60 seconds. This can help to diagnose unexplained freezes during loading/gameplay.
If enabled, and a compatible version of Spark is installed, the entire launch sequence will be profiled until the main menu.
This option may help to detect the cause of chunkloading freezes. However, leaving it enabled may cause slightly worse performance.
Shows a warning on startup if other performance mods considered essential and highly compatible are not present
All versions. If REI or JEI are installed, construction of the vanilla search trees for creative searching is disabled, and searching is instead done using these mods' search implementations. This saves several seconds during world loading, and probably also saves some RAM as well (although I have not measured).
All versions. Avoids creating fresh copies of enum arrays each time a blockstate cache is initialized. Minor optimization, but easy to do.
All versions. Memoizes the RenderMaterial (texture) collection and dependency list that models return instead of requiring them to be recalculated on each request. Helps accelerate the model load/bake process.
Avoids pointlessly creating a URL object and speeds up skull block rendering.
All versions. Saves the generated list of stronghold positions with the world, instead of regenerating it on every world load. Saves a little bit of time on 1.16, and quite a bit more on 1.18 and 1.19.
All versions. Many mods ship outdated structure files, which requires the game to upgrade them using DFU every single time they are loaded. This can be quite slow. This patch adds logic to instead save the upgraded version of the structure, and reuse it on the next load. To handle the case that the mod changes a structure file but not the name, the original file's hash is compared against the cached version, and if they do not match the structure will be upgraded again.
Reduces memory usage by clearing mapping data structures in Fabric Loader that are either redundant or rarely used by mods. Off by default for compatibility reasons.
Force-loads all mixins when launch finishes and then clears out mixin data structures to remove most of Mixin's memory footprint. Disabled by default for compatibility reasons.
Fixes memory waste caused by some legacy servers (e.g. Hypixel) sending empty chunks as if they contain blocks. Reduces memory usage significantly on these servers.
(Fabric) Experimental option that reduces the memory usage of registries by roughly 50%. Not useful in most modpacks unless they contain millions of blocks and items.
All versions. Moves resource pack and data pack reloading to a dedicated worker pool instead of using the default Worker-Main threads. This allows mods to Smooth Boot to still potentially improve singleplayer performance at runtime while not slowing down launch due to a limited thread count.
Deduplicates climate parameter objects used by the new biome system, can save ~2MB but also slows down datapack reload somewhat.
All versions, but disabled by default due to load time impact. Deduplicates resource location namespaces and paths. This saves RAM but also increases the cost of constructing a new ResourceLocation by quite a bit.
Makes most wall blocks share the same shape object instead of each one having its own copy. Can reduce memory usage substantially when lots of wall blocks are added by mods.
All versions. Modifies DFU initialization to happen the first time something needs to be upgraded. This sounds similar to LazyDFU but is distinctly implemented, as it avoids loading any DFU classes/data structures, while LazyDFU only disables rule optimization. Essentially, this option is a safer version of DataFixerSlayer as it will still load DFU when needed.
You should typically continue to use LazyDFU even with this option enabled, as otherwise DFU rule optimization will cause lag.
Constructs entity models the first time they are seen instead of during launch. Some mods are not compatible with this option and will cause EntityRenderer crashes.
All versions. See https://github.com/embeddedt/ModernFix/wiki/Dynamic-Resources-FAQ.
All versions. Allows the game to unload sounds, instead of sounds indefinitely persisting after being loaded.
All versions. Allows the game to unload structure files after generation concludes instead of keeping them loaded forever.
Mitigate lag when there are hundreds of thousands of suggestions while typing a command
All versions. Avoids rendering the sides of items in GUIs. (Yes, vanilla appears to do that.)
This can triple FPS with a mod like REI/JEI installed on weaker GPUs, if enough items are visible. Disabled by default since it's new and not tested much, but should be safe. The most likely issue is items being completely invisible in GUIs, or appearing flat in the world.
All versions. Enables the game to use a faster texture stitching system originally written by SuperCoder79 for lwjgl3ify on 1.7.10, which can save some time during loading. Rarely, it's been reported to cause weird artifacts on blocks or in GUIs, this may be a Sodium bug.
Fixes Minecraft's built-in wait function consuming excessive amounts of CPU resources.
All versions. Implements optimizations to speed up the model loading process.
Fixes an issue causing registration of blocks/items to slow down proportional to the number already registered. This improves startup time.
All versions. Uses a more efficient backing map for compound NBT tags that deduplicates key names and also uses an array map for very small compounds. This reduces the overhead of storing many compound tags in memory.
All versions. A key optimization. Newer Minecraft versions (after 1.12) implemented a blockstate cache system that caches frequently used information about a blockstate, such as whether it is solid, its collision shape, etc. Rebuilding this cache is quite fast in vanilla (it takes only a second or two) but is quite slow with many mods installed, as there are many more blockstates present in the game which all must have their caches rebuilt.
This problem is exacerbated by Forge as the cache is rebuilt at many points when the data would almost certainly be unused before the next rebuild. Examples include right before reaching the main menu (during the "Freezing data" stage), as well as multiple (!) times when a world is being loaded.
ModernFix solves this performance bottleneck by instead making cache rebuilds lazy. Each blockstate rebuilds its cache the first time the data would be accessed. At any point when vanilla or Forge would attempt to rebuild caches for all blockstates, this is redirected to simply invalidate the cache on each blockstate instead.
This should not have any impact on TPS after startup concludes.
All versions. Removes the biome temperature cache as Lithium does on modern versions.
Completely removes spawn chunks from the game. They are no longer loaded at all, unlike Ksyxis.
All versions. A key optimization. Launches on modern versions are heavily bottlenecked by filesystem access. Many requests are frequently made to resource packs to list resources or check if a given resource exists, and each of these result in a very slow file API call.
ModernFix completely eliminates most of the bottleneck here by simply caching a listing of all resources that exist within mod-provided and vanilla resourcepacks. The cache is rebuilt on resource reload (except for the vanilla resources, since they should never change while the game is running).
There are no known compatibility issues with this patch except for OptiFine (its CTM resources do not load correctly). However I do not recommend using OptiFine in any scenario, as it adds several minutes to launch time by itself and is not tested with ModernFix at all.
All versions. Enabled only if FerriteCore is installed. Takes advantage of FerriteCore's handling of blockstates to speed up their creation. This can help speed up launch with mods that add lots of blockstates, such as furniture mods.
All versions. Adjusts the worker and server thread priorities to be lower than the client thread. This helps improve FPS stability on machines with few CPU cores, provided that the Java implementation in use respects priorities.
Concurrency patches to prevent crashes during launch