Unexpected latency issue

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23 Nov 2022 00:08 #257409 by andypugh
Replied by andypugh on topic Unexpected latency issue
You might scrape by if using a Mesa or Pico card, but not if you are using the parallel port. (Sorry, I have not read back to find out)

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23 Nov 2022 01:31 #257415 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
No worries. Thank you. I am using Mesa hardware. At this point I guess I'm just going to look for a good used Optiplex. At least that way I'll have a little piece of mind when running the machine. Thank you all so much for your help. This forum is awesome.
The following user(s) said Thank You: tommylight

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24 Nov 2022 00:14 #257531 by andypugh
Replied by andypugh on topic Unexpected latency issue
You might as well continue with what you have for now. The configs are portable. And you might find it works fine.

Make some parts, worst case you break some tools.

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30 Nov 2022 00:24 - 30 Nov 2022 00:29 #258058 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
Update: I bought a used desktop PC (as suggested) along with a monitor, keyboard, etc. The PC is a Lenovo M93P Tiny desktop model with an i5 2.9ghz CPU, 8GB RAM, and a 256GB HDD. Surely I thought this would suffice. I always read about an older desktop being good enough to use for CNC and run the RT kernal. I went through the install process of LinuxCNC. HORRIBLE latency test results. Can you guys help me out? Now I'm just throwing money away. I have 2 GLX Gears open with a few internet windows and I can barely type this response. I have already gone into the BIOS and disabled any power saving or unnecessary features. This is the slowest system I have seen in awhile. Please help.
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Last edit: 30 Nov 2022 00:29 by LucasWorx.

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30 Nov 2022 01:38 #258069 by tommylight
Replied by tommylight on topic Unexpected latency issue
Did you disable hyperthreading and C states?
I had an M93P till about 2 years ago, most of my LinuxCNC testing and setting up was done on it so i know it had very good latency.
That same M93P is still running a machine with Mesa 7i92 daily. It was not slow...
Did you by any chance disable multicore/multiprocessor support? That will cripple the PC for sure.
The only difference with yours was a faster 4 core processor, 3.8 turbo i think, probably 4770.
Take some pictures of the BIOS, i do not recall what was in it.

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30 Nov 2022 02:13 - 30 Nov 2022 02:32 #258077 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
Yes sir. The first thing I did was go through the BIOS and disable a bunch of stuff. Hyperthreading is disabled and C states is set at C1 (as low as I could go). Looks like a 4570T so you were pretty close. I notice it only says 2 cores though:/ I thought it should've read 4. I did not yet disable the multiprocessor support. I thought that would make it even worse. How does disabling the processing power/support help the PC rather than make it even slower? I'll give that a shot right now. Is it better to allocate more or less RAM to the video card? I have that option as well, from 32MB to 1024MB.
Links to BIOS pictures:
drive.google.com/file/d/16Cgu23AwxzYIaPk.../view?usp=share_link
drive.google.com/file/d/16ELIdnWIuNs64Ai.../view?usp=share_link
drive.google.com/file/d/16LDx8lLA63Y47WJ.../view?usp=share_link
drive.google.com/file/d/16G8nqjDNJ0y_P5N.../view?usp=share_link
drive.google.com/file/d/16OtHkAC-gvWqYPe.../view?usp=share_link
drive.google.com/file/d/16XbhWJwSZWiVy5x.../view?usp=share_link
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Last edit: 30 Nov 2022 02:32 by LucasWorx. Reason: Adding links

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30 Nov 2022 03:39 #258087 by LucasWorx
Replied by LucasWorx on topic Unexpected latency issue
I've disabled about every option in the BIOS and reduced the video card allocated RAM. I ran the histogram for a bit with some stuff open and then I ran the latency test as well. I'm still showing 7 figures on the latency test with just a few internet windows open and 1 terminal. This is ridiculous.
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30 Nov 2022 09:01 #258101 by rodw
Replied by rodw on topic Unexpected latency issue
The only thing I can think of is failing hardware generating spurious interrupts that consume processor time.
I would reseat all memory chips and and cards in the machine. but thats an outside chance.

I als notice a big disconnect between the 2 latency test methods. the histogram is much better.

Could you try
latency-histogram --nobase --sbins 1000

and share the screen dump?

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01 Dec 2022 16:24 #258227 by andypugh
Replied by andypugh on topic Unexpected latency issue
There is something very odd going on here, your latency test results are worse than I see running LinuxCNC on a VM on my Mac!

You could try the RTAI kernel instead.

linuxcnc.org/docs/stable/html/getting-st...#cha:Installing-RTAI

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