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Successfully configured with stepconf: but +Y-axis "stutters" running G-code

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4 years 6 months ago #240550 by tommylight
Replied by tommylight on topic Successfully configured with stepconf: but +Y-axis "stutters" running G-code
forum.linuxcnc.org/18-computer/38838-har...sts-used-pc-s#163885

Adding some memory might help a lot, but not always.
I do have a Dell Optiplex 760 that works perfectly well with 4GB of RAM and RT 5.10 kernel, even for software stepping at 80K to 100K base period.
ASUS ROG Crosshair VIII Impact - AMD X570

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4 years 6 months ago #240559 by RGH
Replied by RGH on topic Successfully configured with stepconf: but +Y-axis "stutters" running G-code
Assuming we are still talking the same machine configuration (didn't read everything - just skimmed through the posts) - the 8GB should be plenty! I have machines running LinuxCNC  happily with 2GB.

@Clung - my 2cents if you care :
Tackle the issue at hand and stop doing unrelated overly complicated stuff - just keep it really simple stupid and cut to the chase.
  • Did you test the kernel config I suggested for preempt-rt? What was the result? Did the interrupt isolation work? Did you check by watching /proc/interrupts?
  • Why 64-bit RTAI that is considered for "the more adventurous"?  Why not the bulletproof 32-bit RTAI?
  • Why 3 hdds? Why multiboot?
  • Why running from USB?
And sorry if some of the points don't really apply or I seem ignorant as for the reasons - really TLDR all those past pages and I lost the thread @ favorite editors and text adventures ;-)

I would suggest:
  • Just disconnect everything but one hard disc that you are prepared to wipe completely
  • Install the original 2.7 32bit RTAI iso  ( www.linuxcnc.org/iso/linuxcnc-2.7.14-wheezy.iso ) on that disc (wiping it of anything that was on there! no multiboot)
  • Test the latency 
    • Use the histogram program, ignore the other tests - the graph allows you (or us) to 'read' what's happening
    • Don't waste time running the test for any length of time if the results are bad - it has no value
  • Adjust the kernel params as required to improve things if required
    • If you don't feel 'grub fluent' install 'grub customizer' to simplifiy playing with the kernel params
=> All this takes roughly an hour if you don't get sidetracked and it quickly verifies if the machine is a lost cause or not

Then, and only then -  if the machine behaves and you are happy with the latency: 
  • Update 2.7 to 2.8.x as per the instructions and setup the machine configuration
  • Do whatever multi-disk / multi-boot fiddling you deem necessary
The following user(s) said Thank You: tommylight

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4 years 6 months ago #240560 by clunc
Replied by clunc on topic Successfully configured with stepconf: but +Y-axis "stutters" running G-code
Thank you, Nebur/passing motorist: a Plan.

I can do that.

I'll answer only two questions, to keep it shortest:
I had done the config changes you suggested, including isolating all but one core. Didn't know to watch /proc/interrupts.
64-bit because it's the natural state for the motherboard (to my way of thinking)--no extra steps required to "throttle down." I am also desperate to get onto a path that is sustainable as machines and linux distributions, which work, age and become harder and harder to find.

My goal is to have a system that is at least straightforward to upgrade: "trivial" would be nice.

@tommylight It is knowing that you have had a number of 780s that worked just fine that has kept my attention on ironing out this one's wrinkles.

On this 780 however, following straightforward steps results in a calibration step that never returns!

I'm off to follow Nebur's proposed method.

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4 years 6 months ago #240561 by RGH
Replied by RGH on topic Successfully configured with stepconf: but +Y-axis "stutters" running G-code
Sorry for the ambiguity - that list of questions I wrote was mostly suggestive and the "cut to the chase" and "keep it simple stupid" was meant in regards to the approach of solving the issue and not to the answering of those questions - that would be really rude ;-)

Anyway - good look!
The following user(s) said Thank You: tommylight

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4 years 6 months ago #240570 by tommylight
Replied by tommylight on topic Successfully configured with stepconf: but +Y-axis "stutters" running G-code
I am sure the 780 can be used, even with 2GB of ram, using the Wheezy ISO.
Alas, some might have memory or hdd or their corresponding controllers failing, power supply with dried capacitors, overheating processor, etc, and all those will mess up the latency, badly.
In my case all of those are easy to deal with as i owned 3 computer shops and i still do high end PC builds so i have plenty of spare parts to test with, also have access to all the local shops for anything i might need testing, i just do not have time for everything i would like to do.
Because of the above i have to refrain from just advising to get a new PC, hell it took me 4 months to get my new PC buying parts one at a time since i have everything invested in machine parts.
Despite all that, i still use some old and some very old Pc and laptops, i like using parallel port as it is very reliable.
So yes, do keep testing, Nebur makes some very good points, and no matter what the results, you have learned something, even if that sometimes means learning what does not work. Done that a lot! :)
How much memory is on the PC?
There are always more than one way of skinning a cat, or a PC, so if you really want to go all in, get the Debian testing non free ISO, install, change repositories to "unstable", do a full upgrade, install LinuxCNC and see how it behaves. This despite being the "beyond cutting edge" has proven good for some old PC and a laptop that was never ever usable with anything.
ASUS ROG Crosshair VIII Impact - AMD X570

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4 years 6 months ago #240594 by andypugh
Replied by andypugh on topic Successfully configured with stepconf: but +Y-axis "stutters" running G-code

I installed LinuxCNC from the Debian 10 .iso onto a 16GB USB thumbdrive and successfully booted into it and then patched it with the RTAI kernel following "Section 7.2" steps in LinuxCNC install.

The very next step was to try to do a calibration run, following Andy's instruction:
% sudo /usr/realtime-4.19.195-rtai-amd64/calibration/run

For reference, on a VM I get this (but obviously the numbers are terrible, it's a VM)
Code:
andypugh@buster:~/linuxcnc-dev/src$ sudo /usr/realtime-4.19.195-rtai-amd64/calibration/run password for andypugh: .runinfo is /usr/realtime-4.19.195-rtai-amd64/calibration/.runinfo No RTAI modules loaded. Running insmod on /usr/realtime-4.19.195-rtai-amd64/calibration/.runinfo... Cleaning up... RTAI successfully unloaded. Removing /tmp/runinfo... Done. andypugh@buster:~/linuxcnc-dev/src$ uname -a Linux buster 4.19.195-rtai-amd64 #5 SMP PREEMPT Sun Jul 11 19:13:27 BST 2021 x86_64 GNU/Linux andypugh@buster:~/linuxcnc-dev/src$ sudo /usr/realtime-4.19.195-rtai-amd64/testsuite/ display latency run andypugh@buster:~/linuxcnc-dev/src$ sudo /usr/realtime-4.19.195-rtai-amd64/testsuite/run .runinfo is /usr/realtime-4.19.195-rtai-amd64/testsuite/.runinfo No RTAI modules loaded. Running insmod on /usr/realtime-4.19.195-rtai-amd64/testsuite/.runinfo... RTAI testsuite and calibration tool (all data in nanoseconds) # period = 100000 (ns) # average time = 1 (s) RTH| lat min| ovl min| lat avg| lat max| ovl max| overruns RTD| -24427| -24427| 19500| 157239| 157239| 3 RTD| -24429| -24429| 19882| 170663| 170663| 4 RTD| -24472| -24472| 19432| 169168| 170663| 10 RTD| -24537| -24537| 18725| 152273| 170663| 14 RTD| -24427| -24537| 18696| 645448| 645448| 21 RTD| -24429| -24537| 19149| 185268| 645448| 27 RTD| -24419| -24537| 19021| 134501| 645448| 30 RTD| -24423| -24537| 19161| 154606| 645448| 31 RTD| -24432| -24537| 18565| 133818| 645448| 35 ^CRTD| -24432| -24537| 18565| 133818| 645448| 35 >>> S = 98.696, EXECTIME = 0.14951 Cleaning up... RTAI successfully unloaded. Removing /tmp/runinfo... Done. But on a real machine I get an error (Which I have seen before, Google gets you back here, but I don't recall the fix) [code]andypugh@rm-one:~$ sudo /usr/realtime-4.19.195-rtai-amd64/calibration/run [sudo] password for andypugh: .runinfo is /usr/realtime-4.19.195-rtai-amd64/calibration/.runinfo No RTAI modules loaded. Running insmod on /usr/realtime-4.19.195-rtai-amd64/calibration/.runinfo... Cleaning up... RTAI successfully unloaded. Removing /tmp/runinfo... Done. andypugh@rm-one:~$ sudo /usr/realtime-4.19.195-rtai-amd64/testsuite/run .runinfo is /usr/realtime-4.19.195-rtai-amd64/testsuite/.runinfo No RTAI modules loaded. Running insmod on /usr/realtime-4.19.195-rtai-amd64/testsuite/.runinfo... CANNOT FIND MAILBOX Cleaning up... RTAI successfully unloaded. Removing /tmp/runinfo... Done. The odd thing is that the second machine, if I run the normal linuxcnc "latency_test" gives me this, which is astonishingly good:
[/code]
Aaaargeh!!!! This editor is absolutely unusable. I have spent 20 minutes trying to get this reply formatted right, in both the source view and the normal view. It simply isn't possible, and every time you change view it moves all the tags to the end. 

I am very close to deleting the entire forum and giving up!

Sorry, you will have to work out for yourselves whoe said what, and what was code. I have donemy best and it was not good enough. 

But there was meant to be a screenshot. 

 

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