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spark

spark is a performance profiling plugin/mod for Minecraft clients, servers and proxies.

Useful Links

What does spark do?

spark is made up of three separate components:

CPU Profiler Memory Inspection Server Health Reporting
Diagnose performance issues. Diagnose memory issues. 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/mod.
  • 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 next item)
  • 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 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.

For a comparison between spark, WarmRoast, Minecraft timings and other profiles, see this page in the spark docs.

License

spark was originally a fork of WarmRoast, which is licensed under the GNU General Public License.

spark itself is also licensed under the GNU General Public License.