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Insufficient System Memory

The JVM crashes (often writing an hs_err log) saying there is insufficient memory or that a native allocation failed. This is the operating system running out of RAM, not the Minecraft heap, so it is different from a Java heap-space OutOfMemoryError.

What does this error mean?
Beyond the Java heap, the JVM and OS need additional native memory. 'Native memory allocation (mmap) failed' or 'insufficient memory for the Java Runtime' means the system could not provide it, usually because too much was allocated to the heap, other processes are using the RAM, or there is no swap. 
There is insufficient memory for the Java Runtime Environment / Native memory allocation (mmap) failed
Most Common Causes
  • An -Xmx so high it leaves no room for native/OS memory.
  • Other processes consuming the machine's RAM.
  • No swap configured, so brief spikes cannot be absorbed.
  • A container/host memory limit below what Java needs.
  • The OS OOM-killer terminating the process.
How To Diagnose
  1. Check total RAM vs your -Xmx ('free -h').
  2. Look for an hs_err_pid file with memory details.
  3. See what else is consuming RAM ('top').
  4. Check the system log for an OOM-killer message.
Recommended Fixes
  • Lower -Xmx
    Leave 1-2 GB free for the OS and native memory instead of allocating everything to the heap.
  • Free or add RAM
    Close other heavy processes, or increase the machine/container memory.
  • Add swap
    Configure some swap to absorb short memory spikes (not a substitute for real RAM).
  • Respect host limits
    Keep total usage under your plan's memory cap so the OOM-killer does not strike.
Analyze My Log
Frequently Asked Questions

Heap OOM is the Java heap filling up. This is the OS itself out of RAM, often from over-allocating -Xmx.

No, the opposite. Lowering -Xmx leaves room for the native/OS memory the JVM also needs.

A Linux mechanism that kills processes when the system runs out of memory, your server can be its target.