Question about an Intel NUC core-i3

I'm very new to this so please pardon the questions.  I recently acquired an INTEL NUC core-i3 with 8GB of ram. This is intended to drive a MESA 7i76e board on a plasma table.  

tldr; I'm primarily curious to know if the latency results I'm getting are going to work (if that's possible to advise).

I've downloaded the latest iso and  went through performance tuning.  I *think* I've done all the things.  It's sometimes hard to follow all the different threads on tuning.

1) Turned off things in BIOS (hyper threading, power management etc.). This left me with two CPUs
2) Grub configured (including isolcpus)
3) CPU governor set to performance
4) IRQ coalescing disabled (intel NIC)
5) CPU core isolated for LinuxCNC (cpu 1) (I am not sure how to confirm this is actually working as intended)
6) Ethernet IRQ pinned to isolated CPU (cpu 1)

The latency histogram as a result looks like this (6 glxgears & running YT videos):
 

~60 us of max latency.   Is this worth continuing to try to use or should I be looking at a better computer?  Any advice appreciated.

I have not hooked it up to the machine yet to try it.  Hope to be attempting that in coming weeks.  Thought I'd post this to see if I need a different computer first.

- Dave

 

Also not sure about the frequency on cpu 1. The governor looks right but current freq = 400Mhz. This doesn't seem good if I understand it right. (again very new to this)

$ sudo cpupower -c all frequency-info
[sudo] password for cnc:
analyzing CPU 0:
driver: intel_pstate
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: Cannot determine or is not supported.
hardware limits: 400 MHz - 2.10 GHz
available cpufreq governors: performance powersave
current policy: frequency should be within 400 MHz and 2.10 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency: Unable to call hardware
current CPU frequency: 2.10 GHz (asserted by call to kernel)
boost state support:
Supported: no
Active: no
analyzing CPU 1:
driver: intel_pstate
CPUs which run at the same hardware frequency: 1
CPUs which need to have their frequency coordinated by software: 1
maximum transition latency: Cannot determine or is not supported.
hardware limits: 400 MHz - 2.10 GHz
available cpufreq governors: performance powersave
current policy: frequency should be within 400 MHz and 2.10 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency: Unable to call hardware
current CPU frequency: 400 MHz (asserted by call to kernel)
boost state support:
Supported: no
Active: no

current CPU frequency: 2.10 GHz (asserted by call to kernel)

All is good, move on to testing on a machine.

Thanks Tommy.

FWIW I've been digging into isolcpus and becoming convinced it's not a good idea on this 2 core CPU at least. Maybe it helps on CPUs with more cores but I am finding very bad results with it here.

I discovered even tho I have isolcpus=1 and I locked the NIC IRQ to CPU 1 rtapi_app was running on CPU 0 during the latency measurements above. When I ran latency-histogram using taskset to lock it on CPU 1 I got horrible latency spikes.

I also found that *all* the IRQs are on CPU 1 which defeats the whole purpose of isolating it.

So I'm going to remove all the CPU isolation optimizations and just run this 2 core setup with the CPU scheduler left to do whatever it decides to do and see what happens. Of course I'll keep all the other optimizations. i.e. power management disabled, governor on performance, etc.

The latency with isolcpus=1 you show is fine. I ran with latency of 120 to 150 us for years and yours is half that!
Just move on for now. Come back if you get an error finishing read.