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MemGuard

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MemGuard

By SeishiroNagiOwner

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Reduces RAM usage in large modpacks and servers by deduplicating NBT strings and monitoring memory usage, without forced GC freezes.

Mod Loaders
Minecraft
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About

Description

MemGuard

Lightweight memory helper for modded Minecraft.
Deduplicates repeated NBT strings and keeps an eye on your heap — without ever freezing your game.

Minecraft 1.20.x Minecraft 1.21.x Forge NeoForge Fabric

🆕 Forge v1.0.5 — no more lag spikes

Older Forge builds (1.0.3 and earlier) forced a full garbage collection every 5 minutes and after every texture atlas upload. In big modpacks that meant a short freeze every few minutes. Version 1.0.5 removes every forced GC: tested in a 364-mod pack, the 609 ms freeze every 5 minutes is gone. If you use MemGuard on Forge, please update.

What MemGuard Does

Feature Description
NBT String Dedup Short, repeated NBT strings (item ids, keys, enum names) share one instance instead of being stored thousands of times. Lock-free and size-limited, so it never slows other threads down.
Memory Monitor Writes a short memory status to the log and warns when heap usage gets risky, so you know when a pack needs more RAM or a lower view distance.
No Forced GC MemGuard never calls System.gc(). The JVM's own garbage collector already runs at the right moments.

MemGuard is a helper, not a miracle: it does not promise specific FPS, MSPT or RAM numbers. For memory leaks, pair it with mods like AllTheLeaks or FerriteCore.

Supported Versions

Loader Minecraft Java Latest build
Forge 1.20 – 1.20.6 17+ v1.0.5
NeoForge 1.21.x 21+ v1.0.4
Fabric 1.21.x 21+ v1.0.1 (update with the same fix coming soon)

Check the Files tab for the exact build per version.

Compatibility Notes

  • Works alongside FerriteCore and AllTheLeaks.
  • Safe to run with -XX:+DisableExplicitGC (common in server packs).
  • If logs mention missing Create classes, check that Create and its addons are on the same update line (Update 5 with Update 5 addons, Update 6 with Update 6 addons). That is not caused by MemGuard.

Quick Install

  1. Install the loader for your Minecraft version.
  2. Put the MemGuard jar for your loader in the mods folder.
  3. Start the game and look for [MemGuard] lines in latest.log.

Support the Project

If MemGuard helps your pack, consider leaving a tip — it keeps the coffee ☕ flowing and the fixes coming!

Buy me a coffee on Ko-fi

Found a problem? Leave a comment with your latest.log — every report helps. 💙

MemGuard

Lean memory behavior for long Minecraft sessions.

MemGuard is a lightweight utility mod for Fabric / Forge / NeoForge (Minecraft 1.21.1) focused on reducing avoidable allocations and making memory pressure easier to observe.

What MemGuard does

1. Reuses repeated short NBT strings

  • Hook: NbtString.of(...)
  • Repeated short values are reused through an LRU cache (up to 2048 entries).
  • This reduces duplicate object allocations for common IDs/tags in larger modpacks.

2. Logs periodic heap snapshots

  • Heap usage is sampled from server tick context.
  • Warning logs are emitted when configured usage thresholds are exceeded.
  • Intended for visibility and troubleshooting, not as a direct performance claim.

3. Tracks texture-atlas lifecycle (client)

  • On atlas upload completion, MemGuard logs heap-used values in debug context.
  • This helps correlate load phases with memory behavior.

Technical notes

  • Uses mixin hooks for targeted behavior (NbtCacheMixin, ServerChunkManagerMixin / ChunkCacheMixin, TextureCacheMixin).
  • No native code, no unsafe memory access.
  • System.gc() is not used to force garbage collection.

Important accuracy notes

  • MemGuard does not guarantee fixed FPS/MSPT/MB improvements.
  • Real impact depends on modpack size, entity/world state, JVM vendor/flags, and session length.
  • Expected benefit is typically higher in medium/large packs with repeated NBT patterns.

Reproducible evaluation (recommended)

To evaluate MemGuard for your own setup, compare baseline vs. MemGuard under identical conditions:

  1. Same Java version, JVM args, mod list, world seed, and config.
  2. Same runtime window (recommended: 30-60 minutes per run).
  3. At least 3 baseline runs + 3 MemGuard runs.
  4. Collect comparable metrics:
  • p50/p95 MSPT (spark or similar)
  • heap usage trend from logs
  • allocation/GC event data (JFR or similar)
  1. Compare distributions (median/p95), not single spikes.

Installation

Fabric

  1. Install Fabric Loader (0.16+)
  2. Install Fabric API
  3. Place MemGuard jar in mods/

Forge / NeoForge

  1. Install the matching loader for your Minecraft version
  2. Place MemGuard jar in mods/

Compatibility

  • Designed to work alongside common optimization mods.
  • As with any mixin-based mod, test your exact modpack before production deployment.