HOW TO AVOID DELAYS

Competition from other threads

resetting a thread to use SCHED_FIFO scheduling ensures that it will run until
- it blocks OR
- yields the processor OR
- a higher priority SCHED_FIFO thread becomes runnable

occur whenever app accesses a memory address that is not currently resident in physical RAM
disk I/O required to bring memory contents into RAM
mlockall(2) prevents memory from being paged out of RAM
still necessary to touch memory before "critical use", because allocated memory is not mapped to RAM until then.

the kernel sometimes blocks all IRQ handling
audio interface IRQ has a deadline for service. if interrupts are blocked for too long, we miss the deadline OR make it impossible to process the available data in time.
user space can't do anything about this - it requires kernel patches, fixes, redesigns.