System Configuration

Kernel Parameters

Agnocast uses POSIX message queues for inter-process notification. The default Linux limits are too low for typical robotics workloads.

Required

Set the maximum number of messages per queue:

bash sudo sysctl -w fs.mqueue.msg_max=256

To persist across reboots, add to /etc/sysctl.d/agnocast.conf:

ini fs.mqueue.msg_max = 256

Optional (for large deployments)

```ini

Maximum number of message queues system-wide

fs.mqueue.queues_max = 1024 ```

Per-user POSIX message queue memory limit

Each bridge manager message queue consumes memory proportional to the maximum message size and queue depth. When running many Agnocast processes simultaneously, the per-user POSIX message queue memory limit (RLIMIT_MSGQUEUE) may be exceeded, causing mq_open to fail.

To increase the limit, either add the following line to /etc/security/limits.conf:

bash * - msgqueue unlimited

Or use prlimit to change the limit for the current shell:

bash sudo prlimit --pid=$$ --msgqueue=unlimited

You can verify the current limit with:

bash ulimit -q

RT Throttling (for CallbackIsolatedExecutor)

If using real-time scheduling with the CallbackIsolatedExecutor, you may need to increase the RT throttling limit. The default allows RT tasks to use 95% of each period:

```ini

/etc/sysctl.d/agnocast-rt.conf

kernel.sched_rt_period_us = 1000000 kernel.sched_rt_runtime_us = 980000 ```

This allows RT tasks to use up to 98% of each 1-second period, leaving 20 ms for non-RT tasks.

Warning

Setting sched_rt_runtime_us = -1 disables RT throttling entirely, which can lock up the system if an RT task runs away. Only use -1 if you fully understand the implications.