MemGuard

# 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) 5. 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.