Latency

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24 Jan 2024 23:13 #291557 by garja
Latency was created by garja
PCW... I was told you know a lot about latency issues.
I'm using a Mesa 7i96S card.
My computer is a Fujitsu i5-6500 3.2 GHZ with 8 MB ram.
I've installed LinuxCNC 2.9.2 Debian Bookworm.
According to the latency test window, kernel version
=#1 SMP-Preempt_RT Debian 6.1.67-1 (2023-12-12)
When I run a latency test I get numbers like 367.
I've tried disabling the onboard graphics and used a PCIe 3.0 AMD video card. Still get the same results. In the CMOS there was a cpu setting that allowed me to use just one thread. Using just one thread yields the same results.
If I run latency-histogram --no base --sbinsize 1000 and 3 glxgear windows, my max (us) is 115.4 after just 300 seconds. It jumps to 167.2 after just 650 second.

Any thoughts that might be helpful to me?

Thanks... Garlen

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24 Jan 2024 23:19 #291559 by PCW
Replied by PCW on topic Latency
Do you get latency related errors when running the 7I96S?

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24 Jan 2024 23:36 #291561 by garja
Replied by garja on topic Latency
Hey... thank you so much for your quick response.

I didn't get any errors just high numbers. I was able to connect to the Mesa 7i96s card and when I ping it I don't get any errors either. John from Mesa mentioned that you had commented

"Also as long as you do not suffer real time errors or Ethernet timeouts the latency is largely irrelevant."

I was able to ping my Mesa card and did not see any timeouts. Maybe there is another way to test to see if I do get any Ethernet timeouts?

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25 Jan 2024 01:14 #291564 by PCW
Replied by PCW on topic Latency
I don't mean ping timeouts but rather latency/communication
errors from LinuxCNC

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25 Jan 2024 02:06 #291566 by garja
Replied by garja on topic Latency
I've only connected the Mesa card and connected through my Ethernet card and pinged it to make sure I had it setup correctly. I've not started the actual setup of Debian Bookworm 2.9.2. I guess my next step is to complete the Pncconf wizard or should I run a Mesa wizard before I do the Pncconf wizard. I guess I'm not sure what to do next.

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29 Jan 2024 11:38 #291884 by vmihalca
Replied by vmihalca on topic Latency
I do get latency errors from linuxcnc. I am using Mesa 7i97.
Debian bookworm, linuxcnc 2.9.2 compiled from sources.
I got max jitter on servo thread 1553904.
On the same PC while I was using debian 10 I had no complains about the latency.
Nothing in the bios was changed since then.
The machine seems to run fine, but I've mostly run test programs as I am still working on it.

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29 Jan 2024 15:49 #291897 by PCW
Replied by PCW on topic Latency

I got max jitter on servo thread 1553904.

That's fairly terrible (about 1/2 ms on a 3 GHz PC)
 Are you sure you are running a real time kernel?
What does

uname -a

report?
 

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10 Feb 2024 23:22 #293043 by garja
Replied by garja on topic Latency
Anyone have any experience with using an HP p6000 Series? It uses an AMD Anthon ll 640 quad core processor. Wondering if anyone knows anything about how good its latency is.

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10 Feb 2024 23:31 #293044 by tommylight
Replied by tommylight on topic Latency
Not me, but if you do run on latency issues, try this first:
forum.linuxcnc.org/38-general-linuxcnc-q...ead-and-irq-affinity
The following user(s) said Thank You: garja

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11 Feb 2024 14:28 #293092 by garja
Replied by garja on topic Latency
Will do. Thanks tommylight
The following user(s) said Thank You: tommylight

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