unexpected realtime delay on task 0

Have you read wiki.linuxcnc.org/cgi-bin/wiki.pl?The_Is...results_for_isolcpus

It mentions other options for isolcpus than the one you said you have tried. Something to investigate if you have 4 or more cores.

If you can state what motherboard or desktop you are trying to use, someone may chime in.

There are one or two threads regarding latency issues and the methods take to resolve the issue on the forum. Maybe worth trying a search or just browsing through the forums.

Here is one forum.linuxcnc.org/18-computer/25927-red...lticore-pc-s-success

i tried these solutions but it's just decrease latency a bit when i start, after around 30-50s latency still spikes up from 8us to 260us. On ubuntu 16.04 with preempt rt kernel the terminal show: Unexpected realtime delay.... On debian 3.4.55-4 (rtai kernel) show nothing but still spike up to from 11us to 130us(core i3)

so, now i 'm testing on 3 pc include: dual core, core i3, core i5. The list what i tried are:
+ Setting BIOS:
- Turn off HT technology, multicore,speedstep, USB legacy support, Virtualization, power saving.
+ Edit grub:
- Add isolcpus= 1; 1,2,3; 2,3 at GRUB_CMDLINE_LINUX_DEFAULT="there is something else here" --> update grub
- Replace isolcpus=1 by radeon.modeset=0 --> update grub
+ following this solotions forum.linuxcnc.org/18-computer/25927-red...success?limitstart=0
+ fixing SMI.

+result: i use this way to test: cd /usr//testsuite/kern/latency then ./run
- with dual core(use liveCD): the latency (lat max) is around 60us with no overrun
- with core i3(use liveCD) : the latency is around 130k with some overruns
- with core i5(use ubuntu 16.04 and preempt-rt): didnt try new solution yet but last result give around 260us
=> these solutions didnt work.

+ next i think i will try change graphic card and disable onboard card. I will update my mainboard soon, hope someone give me some advices

As I mentioned before details (model\manufacturer) of PC's and motherboards will help.

I experimented with a P4 3.0Ghz dell (can't recall the model), I used the Linuxcnc supplied cd, Linuxcnc running on slackware and linuxcnc running on a base built following Linux From Scratch & Beyond Linux From Scratch......from memory the best results I got was from the slackware\linuxcnc combo. I did notice spikes on all 3 combos when using IDE drive interface, not so with SATA.

I eventually got fed up trying to get decent results and opted for a BeagleBone Black and using the PRU for step generation...yeah graphics aren't the best, takes a couple of extra seconds to load......but the programmable realtime units and hardware quadrature encoders are pretty cool. Keeping the HDMI I still have 16 outputs and 18 inputs (as I have the system configured) plus one extra that I can use as either Input or Output.

The above is no way a slight on Linuxcnc, the Developers and of course the forum and it's members. I have learnt far more on this from this forum, wiki & members than anywhere else. It was more a comment on the access to hardware and personal funds available to myself.....I'd bought a BBB a few years ago.

Some people have reported ok results using on board graphics on certain boards.

here is my system info for core i3 and core i5 pc (today i cant turn on dual core pc )

I'm guessing it will have something to do with System management mode, as the dereference in the i3 & i5.

Operations in SMM take CPU time away from the applications, operating system kernel and hypervisor, with the effects magnified for multicore processors since each SMI causes all cores to switch modes. To quote from en.wikipedia.org/wiki/System_Management_Mode .

It may be a case of these machine being unsutiable...maybe this is an uneducated guess.

I did a bit of a search and found this thread on stackoverflow

stackoverflow.com/questions/25399405/eva...x-centos-intel-machi

Link to the manpage of hwlatdetect
manpages.ubuntu.com/manpages/xenial/man8/hwlatdetect.8.html

This will not fix the problem but should give an indication of what is happening. (hopefully)