Unexpected latency issue

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22 Nov 2022 01:32 #257278 by tommylight
Replied by tommylight on topic Unexpected latency issue
Exactly!
If you have a 4 core cpu.
For a two core cpu, =0 or =1
But if the cpu has hypethreading that can not be disabled in BIOS, try =1,3 for a two core cpu, or =1,3,5,7 for a 4 core cpu.

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22 Nov 2022 01:48 #257281 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
Ok great! I believe the core i5's are 4 core cpu's. I tried the =2,3 but it almost seems like it got worse. I'll try =1,3,5,7 tomorrow and give it one more try. I would be really happy if I can get this laptop to run QTPlasmaC more smoothely without the errors but so far it's not looking so good. I'm kinda surprised because even though a laptop is not ideal, I see many people use them without issue and I know many of them have lower specs than the one I'm using. However, maybe I'm asking a bit much by running sheetcam or Inkscape on the same computer:/

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22 Nov 2022 01:56 #257282 by tommylight
Replied by tommylight on topic Unexpected latency issue
Where do you see people using laptops with LinuxCNC running machines????
Those are probably all my videos, i have 3 laptops that can run machines, one only for testing as it uses an USB to Ethernet adapter and still works for hours without dropping the link, on batteries. The best of those got the screen messed up when i left it at a clients site. Shame, as it ran the machine for over two months without ever dropping the link.

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22 Nov 2022 01:59 #257283 by tommylight
Replied by tommylight on topic Unexpected latency issue
Ooops, should have added, the one not mentioned above is an old ACER, also runs machines for days on end, found and bought another one, same model, did not work, gave it to a friend for free. It had utterly useless latency.

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22 Nov 2022 02:08 #257284 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
Hmm, I wonder why the second one wouldn't work like the first:/ To answer your question though, I've seen many videos/users operating their CNC from laptops, but I suppose I wasn't thinking of them running linuxCNC specifically and I probably should've been. My bad. Maybe I need to look into that more....or just save time and follow y'all's advice by getting a desktop. Lol. My apologies. I'm stubborn.

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22 Nov 2022 02:40 #257292 by tommylight
Replied by tommylight on topic Unexpected latency issue
Oh you meant in general using laptops to run machines, sorry it did not light a bulb at the time.
Yes, some do use laptops, some sell machines with laptops, most of those use "USB Mach3" controllers, very often those come here to ask how to replace that.
Back on topic, do some testing, use
latency-histogram --nobase --sbinsize 1000 --show
to test latency, if there are huge excursions in the millions, do not bother anymore, see if there is a way to get into BIOS, otherwise nothing helps.
If the latency remains stable even at 200000 or more with no excursions, there is still hope as the servo period can be longer without affecting machine functionality. Beware that messing with servo period messes up a lot of other things, mostly the PID loop, but more when we get there.

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22 Nov 2022 02:43 #257295 by tommylight
Replied by tommylight on topic Unexpected latency issue

Hmm, I wonder why the second one wouldn't work like the first: I'm stubborn.

Not the same BIOS version, could not find anything as it was over 10 years old, i think. Could not disable hyperthreading.

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22 Nov 2022 14:16 #257334 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
Well, today I tried isolcpus=1,3,5,7. The computer is definitely slower, but the latency is still coming up very high. The BIOS doesn't allow me to adjust very much so I suppose it's time to move things to a desktop:/ Can't say I didn't try though.
The following user(s) said Thank You: tommylight

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22 Nov 2022 20:33 #257373 by rodw
Replied by rodw on topic Unexpected latency issue
I think you are looking for a new PC at this point.

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22 Nov 2022 21:21 #257380 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
I changed the GRUB file back to the original and tried one more time with the histogram. The first result shown is when I had several internet windows open, sheetcam, and 3 GLX gears. The second result shows the spike from the second I opened YouTube and clicked play on a video, Although, I'm not going to be opening YouTube while I'm doing CNC work so I don't know how practical that really is. Do you guys think the first results would skimp by providing I only used this for QTPlasmaC or is it still not looking to great?
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