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Using Spark Profiler

An advanced guide to diagnosing server lag (TPS drops) using the Spark profiler.

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What is Spark?

Spark is a performance profiling plugin/mod that records exactly what your server's CPU is doing. It helps identify which plugin, entity, or mod is causing lag.

Installation

If you are using Paper or Purpur, Spark often comes pre-installed or can be easily added.

1. Download Spark.
2. Upload the .jar to your /plugins/ (for Paper/Spigot) or /mods/ (for Fabric/Forge) folder.
3. Restart the server.

Running a Profiler

When your server starts lagging (low TPS), run the following command in-game or in the console:

This will record data for 120 seconds.

Analyzing the Results

Once the profiler finishes, it will generate a link (e.g., https://spark.lucko.me/abc12345). Click this link to open the viewer.

Key things to look for:

• Server Thread (bottom up): Expand this tree to see what is consuming the "tick".
• Entities: If net.minecraft.world.entity is high, you likely have too many mobs or entities in a specific area.
• Plugins: Look for plugin names in the tree. If a specific plugin is taking up >10% of the tick, it might be the cause.

Common Fixes

• High Entity Usage: Use a plugin like ClearLag (sparingly) or reduce mob spawn rates in bukkit.yml.
• Bad Plugin: Check if the plugin has an update or remove it.
• Chunk Loading: Pre-generate your world using a plugin like Chunky to prevent lag from generating new terrain.