SCHED_FIFO higher priority thread is getting preempted by the SCHED_FIFO lower priority thread?

Question

I am testing my multithreaded application in Linux RT multicore machine.

However during testing, we are observing that real time Thread switch(created with SCHED_FIFO sc

Answer 1

There could be two reasons:

• CPU throttling: the scheduler is designed to reserve some CPU time to non-RT tasks; you have already disabled it by acting on the /proc/sys/kernel/ entries
• blocking: your high-priority task is blocking either
  • on some synchronization mechanism (e.g., mutex, semaphore) or
  • on some blocking call (e.g., malloc, printf, read, write, etc.)