RLCraft Server Lag: Fixes That Work (1.12.2, v2.9.3)
Published
RLCraft lag usually comes from one of three things: not enough memory, one overloaded server thread, or too many entities and loaded chunks. Throwing RAM at it only helps the first. Here's how to tell which one you have, in about ten minutes.
This guide is for the current RLCraft release, v2.9.3 on Minecraft 1.12.2 (Forge 2860 or newer, which the pack ships with). It runs on Java 8 (which Java each Minecraft version needs).
Step 1: measure instead of guessing
Install spark, the standard Minecraft profiler. Its download page lists a Forge 1.12.2 build among older versions, described as not actively supported but still working, so commands may differ slightly from newer docs; run /spark to see what your build offers.
On current spark builds:
/spark tpsprints the server's ticks per second. 20 is healthy; sustained numbers under about 18 are noticeable lag./spark healthshows memory and CPU in a live view./spark profiler start, play (or let the lag happen) for a few minutes, then/spark profiler stop. The result is a link to a report showing what spent the time.
How to read it:
| What you see | What it means | What to do |
|---|---|---|
| Memory sits near the limit and keeps climbing, or the server crashes with an out-of-memory error | Not enough RAM | Add RAM (see sizes below) |
| Memory is fine, but TPS drops | The main thread is the limit (CPU-bound) | Reduce load (steps 2-4); more RAM won't help |
| Short, regular freezes every few seconds to minutes | Garbage collection pauses, or chunk generation as players explore | Check memory headroom; see step 3 |
Step 2: lower the load on the main thread
- View distance. In
server.properties, tryview-distance=8(or lower), then restart. In 1.12.2 there is no separate simulation distance setting, so view distance is the main lever. - Dropped items and mobs. Piles of dropped items and large mob groups cost ticks. Spark's profile shows which entities cost the most.
- Chunk loaders and farms. Anything that keeps many chunks loaded around the clock keeps ticking even when nobody's looking.
Step 3: exploring lag
When players run into unexplored land, the server generates terrain on the spot, which causes spikes. Many modern packs fix this by pre-generating with Chunky, but note that Chunky's oldest supported version is 1.13.2, so it can't be used on RLCraft's 1.12.2. Instead, keep players from all sprinting in different directions at once, and keep a world backup before large expeditions.
Step 4: pick a sensible size
The RLCraft CurseForge page recommends 3 to 4 GB for the client (the default 1 GB is not enough). A server needs more because it runs the world for everyone. On Packyard:
- RLCraft's minimum and recommended plan size is 5 GB on the order page.
- Our modpack RAM guide suggests 6 GB for 2 to 5 players, 8 GB for 6 to 10 and 10 GB for 10 to 20, and rates RLCraft's CPU load as low to medium. Those larger numbers are estimates based on public pack listings and our rule of thumb, not benchmarks, and the guide says so.
- Our own provisioning check of RLCraft on a 5 GB plan took about 4.5 minutes from order to the server answering a status ping (266 seconds). First boot is slow; wait it out.
- For comparison, a newer RPG-style pack like Vault Hunters starts at 8 GB, because every vault is generated as its own area (Vault Hunters 3 server RAM).
More than the recommended size rarely cures lag. If spark says memory is fine, spend your effort on steps 2 and 3.
Step 5: setup details people miss
- The RLCraft server pack's
server.propertiesneedsenable-command-block=true. The pack's CurseForge page says some structures may not generate and villagers may be missing without it. - Players need the same RLCraft version on their client as the server runs.
- Make a backup before changing configs. On Packyard you can make your own backup in the panel and restore it with one click.
Run it on Packyard
Packyard installs the RLCraft server pack for you with the right Java version, and the server stays on with a permanent address (yourserver.play.packyard.ca). RLCraft starts at 5 GB, which is $7.50 a month ($1.50 per GB of RAM, USD plus applicable taxes). You can edit configs in the panel's file manager or over SFTP, and add friends as sub-users who help run it without seeing your billing. Available in the US and Canada (not Quebec); servers are in US West.
Run RLCraft on Packyard from $7.50, or read the RLCraft server hosting page and our step-by-step RLCraft server guide.
RLCraft belongs to its creators. Packyard is not affiliated with RLCraft, Mojang or Microsoft.
FAQ
How much RAM does an RLCraft server need?
We sell it from 5 GB. For 2 to 5 players our RAM guide suggests 6 GB, and more only if spark shows you're out of memory.
Why is my RLCraft server lagging even with plenty of RAM?
Minecraft runs most of the world on one thread. If that thread can't keep up, more RAM changes nothing. Use spark to find what's slow.
Does RLCraft work on Java 21?
RLCraft is a Minecraft 1.12.2 pack and runs on Java 8; we set the Java version for you when you order.
Can I use Chunky to pre-generate RLCraft?
No. Chunky supports Java Edition 1.13.2 and newer; RLCraft is 1.12.2.
Can Bedrock players join?
No. RLCraft is a Java mod pack, and Packyard is Java Edition only.
More guides and posts on the Packyard blog.