Troubleshooting

mlock Issues

EPERM: Operation not permitted

Cause: Missing CAP_IPC_LOCK capability.

Solution:

# Docker
docker run --cap-add=IPC_LOCK ...

# systemd
AmbientCapabilities=CAP_IPC_LOCK

# setcap
sudo setcap cap_ipc_lock+ep /usr/bin/my-daemon

ENOMEM: Cannot allocate memory

Cause: Memlock ulimit exceeded.

Solution:

# Docker
docker run --ulimit memlock=-1:-1 ...

# systemd
LimitMEMLOCK=infinity

# shell
ulimit -l unlimited

Container Issues

Daemon deadlocks under memory pressure

Cause: Memory not locked, daemon pages being swapped.

Solution:

docker run --cap-add=IPC_LOCK --ulimit memlock=-1:-1 ...

See Memory Locking for full details.

General Issues

Daemon fails to start

1. Check logs: journalctl -u my-daemon
2. Verify configuration: my-daemon --check-config
3. Check permissions on binary and config files
4. Verify resource limits are reasonable

High memory usage

1. Check for memory leaks with heaptrack or valgrind
2. Review VmRSS in /proc/<pid>/status
3. Ensure mlock is not locking more than needed