If you're experiencing issues with IO (Input/Output) limits not working on an XFS filesystem, there are a few potential reasons and troubleshooting steps you can take:

1. Verify IO Limits Configuration:

   Double-check that you've configured the IO limits correctly. This may involve checking the configuration files, system settings, or commands used to set the limits.

2. Check for IO Scheduler:

   Verify which IO scheduler is in use. Some schedulers may not respect IO limits as expected. For example, the "loop" scheduler doesn't perform any IO scheduling and could potentially bypass limits.

   You can check and change the scheduler with commands like cat /sys/block/sdX/queue/scheduler and echo SCHEDULER_NAME > /sys/block/sdX/queue/scheduler.

3. Kernel and Filesystem Versions:

   Ensure that your kernel and XFS filesystem are up-to-date. Sometimes, issues related to IO limits can be resolved by updating to a newer kernel or file system version.

4. Testing with Different File Systems:

   Test if the same IO limits are working on a different file system like ext4. This will help determine if the issue is specific to XFS or if it's a system-wide problem.

5. Consider Using groups:

   If you're managing resources for specific processes, you might consider using groups (control groups) for finer-grained control over resource allocation. This can be especially useful in containerized environments.

6. Monitor Disk Activity:

   Use tools like iostat, iotop, or sar to monitor disk activity and see if the IO limits are being violated. This can give you insight into what's happening at the system level.

7. Check for Any Custom Scripts or Tools:

   Make sure there are no custom scripts or tools running that might interfere with IO limits.

8. Review Kernel and Disk Driver Logs:

   Check system logs for any messages related to IO or disk activity. This might provide clues about what's happening.

9. Community and Support Forums:

   Seek help on community forums or support channels specific to your operating system or distribution. Others might have encountered similar issues and found solutions.

10. File a Bug Report:

If you're unable to resolve the issue, consider filing a bug report with the developers of the relevant software components (kernel, file system, etc.).

Remember to always backup critical data before making any significant changes to your system, especially if you're testing different configurations or settings.