Hi, On 11/15/18 11:32 AM, Mohsen Alizadeh Noghani wrote:
Hello everyone. I'm using 4.4.162-rt175 and a core i3-4170 processor. I would like my only real-time process (1 thread) to run on an isolated core, without interruptions by the local timer. * Support for fully tickless opration is enabled in the kernel configuration CONFIG_NO_HZ_FULL=y
I can't remember if v4.4-rt works with CONFIG_NO_HZ_FULL correct. IIRC this has been addressed in later versions of the -rt patch set.
You should try first with a more recent version and see if you get your setup working.
* Kernel boot parameters for isolating CPU 1, isolcpus=1 nohz=on nohz_full=1 rcu_nocbs=1 However, even when I haven't assigned any process to CPU 1, it's being interrupted by the timer tick at a rate of 1 KHz (HZ_1000=y), as seen in the output of cat /proc/interrupts
Looks like nohz didn't work.
1- Is there something I'm missing in the configuration or boot parameters? 2- If tickless operation is not possible, what is the second-best combination of timer tick handling and timer frequency configurations? Is "Periodic timer ticks" preferable to "Idle dynticks system"? Is a lower timer frequency better as the only process on the isolated CPU gets interrupted less?
Generally, nohz and -rt is not the best configuration. Obviously it depends on your needs. Periodic timer ticks will give you the best (read smallest) latency performance.
Thanks, Daniel
