spark

spark is a performance profiler for Minecraft clients, servers and proxies.

Useful Links
Website - browse the project homepage
Documentation - read documentation and usage guides
Downloads - latest plugin/mod downloads

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What does spark do?

spark is made up of three separate components:

CPU Profiler: Diagnose performance issues.
Memory Inspection: Diagnose memory issues.
Server Health Reporting: Keep track of overall server health.

⚡ CPU Profiler

spark's profiler can be used to diagnose performance issues: "lag", low tick rate, high CPU usage, etc.

It is:

Lightweight - can be ran in production with minimal impact.
Easy to use - no configuration or setup necessary, just install the plugin.
Quick to produce results - running for just ~30 seconds is enough to produce useful insights into problematic areas for performance.
Customisable - can be tuned to target specific threads, sample at a specific interval, record only "laggy" periods, etc
Highly readable - simple tree structure lends itself to easy analysis and interpretation. The viewer can also apply deobfuscation mappings.

It works by sampling statistical data about the systems activity, and constructing a call graph based on this data. The call graph is then displayed in an online viewer for further analysis by the user.

There are two different profiler engines:
Native AsyncGetCallTrace + perf_events - uses async-profiler (only available on Linux x86_64 systems)
Built-in Java ThreadMXBean - an improved version of the popular WarmRoast profiler by sk89q.

⚡ Memory Inspection

spark includes a number of tools which are useful for diagnosing memory issues with a server.

Heap Summary - take & analyse a basic snapshot of the servers memory
A simple view of the JVM's heap, see memory usage and instance counts for each class
Not intended to be a full replacement of proper memory analysis tools. (see below)
Heap Dump - take a full (HPROF) snapshot of the servers memory
Dumps (& optionally compresses) a full snapshot of JVM's heap.
This snapshot can then be inspected using conventional analysis tools.
GC Monitoring - monitor garbage collection activity on the server
Allows the user to relate GC activity to game server hangs, and easily see how long they are taking & how much memory is being free'd.
Observe frequency/duration of young/old generation garbage collections to inform which GC tuning flags to use

⚡ Server Health Reporting

spark can report a number of metrics summarising the servers overall health.

These metrics include:

TPS - ticks per second, to a more accurate degree indicated by the /tps command
Tick Durations - how long each tick is taking (min, max and average)
CPU Usage - how much of the CPU is being used by the server process, and by the overall system
Memory Usage - how much memory is being used by the process
Disk Usage - how much disk space is free/being used by the system

As well as providing tick rate averages, spark can also monitor individual ticks - sending a report whenever a single tick's duration exceeds a certain threshold. This can be used to identify trends and the nature of performance issues, relative to other system or game events.

Usage
To install, just add the .jar file to your mods directory.

Information about how to use commands can be found in the docs.

If you’d like help analysing a profiling report, or just want to chat, feel free to join us on Discord.

Guides
There are a few small "guides" available in the docs, covering the following topics.
The tick loop
Finding the cause of lag spikes

ABOUT THIS LISTING

This page describes spark by lucko. The description and screenshots are the author's own, imported from their listing on Modrinth on 24 October 2026: https://modrinth.com/mod/spark

Mythiq.net hosts no files for it. The download button goes straight to the release file on cdn.modrinth.com, so you are downloading from the author's own host, not from a copy of ours.

The download count, rating and comments on this page start at zero and count Mythiq.net only. The source's own figures are not copied here — they measure a different site, and a number that cannot be checked against our own ledger is not worth printing.

MOD LOADER

This release is built for Neoforge. A mod built for one loader will not load under another — Fabric mods do not run on Forge, and vice versa.

GAME VERSION

Built for Minecraft 26.3, 26.2, 26.1.2, 26.1.1, 26.1. Minecraft mods are tied to an exact version: a 1.21.4 build will refuse to load on 1.21.5.

DEPENDENCIES

Check the author's listing for required libraries before you start the game — a missing dependency shows up as a crash on launch, not as a warning.

1. Install Neoforge for the Minecraft version you play, if you have not already.

2. Download the .jar with the button on this page. Do not unzip it — a mod jar is installed as it is.

3. Put it in your mods folder:

Windows — %APPDATA%\.minecraft\mods

macOS — ~/Library/Application Support/minecraft/mods

Linux — ~/.minecraft/mods

4. Launch the game with the Neoforge profile selected.

ON A SERVER

Anything that changes world generation or gameplay has to be installed on the server as well as on every client. Client-side visual and interface mods do not.

UPDATING

Replace the old .jar rather than adding the new one beside it. Two versions of the same mod in the folder is a crash on launch.