Re: Kernel schedules kernel tasks on isolated cpus, SCHED_FIFO prevents kernel tasks from running

On Wed, 2017-06-28 at 08:39 -0500, Andrei Hurynovich wrote:

Hi.

We are trying to build realtime(-ish) system based on rhel6(kernel  2.6.32-642.1.1.el6.x86_64).

We used isolcpus to remove some cpus from process  scheduling(isolcpus=2-19 nohz_full=2-19 rcu_nocbs=2-19).

We spin off a program thread that set's its cpu affinity to one of those  isolated cpus, sets its scheduling chass to SCHED_FIFO, spins in a loop  and never sched_yield()-s to the kernel.

We set sysctl kernel.sched_rt_runtime_us = -1 so realtime threads are  NEVER interrupted.

You want an actual realtime kernel for that to work right. The real time kernel currently supported by Red Hat is 3.10 based, not 2.6.32 based. -- All rights reversed