How to Adjust Your Minecraft Server's RAM Allocation
Set the right amount of RAM for your Minecraft server type, and use Aikar's optimized JVM flags to get better performance out of every gigabyte.
Where to Set RAM in WISP
RAM allocation is controlled by JVM startup flags in the WISP panel:
- Go to the Startup tab in your WISP panel.
- Find the Java Startup Command or JVM Arguments field.
- Look for (or add)
-Xmsand-Xmxflags:
-Xms2G -Xmx4G
-Xms— Minimum (starting) heap size-Xmx— Maximum heap size
Set both to the same value if you want a stable memory footprint and don't want the JVM to resize constantly. For example, -Xms4G -Xmx4G.
How Much RAM Do You Need?
| Server Type | Recommended RAM |
|---|---|
| Vanilla (1–10 players) | 1–2 GB |
| Vanilla (10–30 players) | 2–4 GB |
| Paper/Spigot with plugins (10–30 players) | 2–4 GB |
| Paper/Spigot with plugins (30–100 players) | 4–8 GB |
| Small modpack (under 50 mods) | 4–6 GB |
| Medium modpack (50–150 mods) | 6–8 GB |
| Large modpack (150+ mods) | 8–12 GB |
These are starting points — watch your actual memory usage in the WISP panel and adjust up if you're consistently near the limit, or down if you're well under it.
The 75% Rule
Never allocate more than 75% of your server's total RAM to Minecraft. The operating system and other processes need headroom. On a 8 GB server, don't go above -Xmx6G. Starving the OS causes slowdowns and crashes that look like Minecraft problems but aren't.
Aikar's Flags (Recommended for Paper)
If you're running Paper or Spigot, Aikar's flags significantly improve garbage collection behavior — less lag spikes, more stable performance. Replace your JVM arguments with:
-Xms6G -Xmx6G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+ProvidesDefaultStandardResolutionOnly -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true
Adjust the -Xms6G -Xmx6G values to match your server's allocation. The rest of the flags can be used as-is.
The official, up-to-date version of these flags is at https://docs.papermc.io/paper/aikars-flags.
Checking Memory Usage
In the WISP panel, the Console or Overview tab shows real-time memory usage. In-game (with OP), you can also run:
/gc
(on Paper/Spigot) to see heap usage and trigger a garbage collection cycle.