Which way could guarantee more precise delay?'rt_task_sleep' or 'rt_task_wait_period'?

[孙世龙 via Xenomai]

Hi,
       I need to run a simpe routline periodically.For example,
the routline needs to run every 1ms.

       Which way could guarantee more precise delay?'rt_task_sleep'  or
'rt_task_wait_period'?

       If there is a better solution,please let me know.

       Thank you for attention to this matter.
       Look forward to hearing from you.