Analyzing Lag with Spark

Spark is like an X-ray for your server. Instead of guessing why things are slow, it shows you exactly which plugin, mod, or entity is eating up your CPU. It’s the ultimate tool for any serious server owner running Paper, Fabric, or Forge.

1. Getting It Set Up

Paper/Spigot: Just head to the Plugins tab in Mission Control and install it from the catalog.
Fabric/Forge: Download the mod version from Modrinth and drop it into your mods/ folder.

2. Running Your First Profile

When the lag starts, run this command in-game or in the Console:

/spark profiler start

Let it run for 3-5 minutes so it captures enough data. When you're ready, stop it:

/spark profiler stop

The server will give you a link, so click it to see your report!

3. How to Read a Flame Graph

When you open the link, you'll see a Flame Graph. It looks complicated, but it's simpler than you think:

Width = CPU Usage: The wider a "bar" is, the more work it's doing. Focus on the wide bars at the top.
Top-Down: The top bars are the actual tasks being run; the bars below them are just the categories they belong to.
Colors: Human-made stuff (plugins/mods) usually stands out from the gray Minecraft internals.

What to Look For

Culprit	Clue in the Graph
Too Many Mobs	Look for `EntityTick` or specific names like `EntityVillager`.
Heavy Plugins	Look for the name of the plugin (e.g., `LuckPerms` or `WorldEdit`).
New Chunks	Look for `ChunkProvider` or `ChunkGenerator`.

4. Useful "Quick Check" Commands

/spark health: A quick look at your TPS (ticks per second) and memory.
/spark tps: See if your server has been lagging recently or if it's a new issue.
/spark gc: Shows you a graph of your RAM usage; it's great for spotting "memory leaks."

Still confused by the graph? Our Discord community is full of performance nerds who love reading these. Drop your link in #support!