Latency, error finishing read, and IRQ affinity

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10 Feb 2024 18:43 #293024 by Mecanix

It should be run from /etc/rc.local and not as a policyscript for irqbalance.


Ah. You actually did mentioned, missed it, sry. 
$ sudo nano /etc/default/grub

    #GRUB_CMDLINE_LINUX_DEFAULT="quiet"
    GRUB_CMDLINE_LINUX_DEFAULT="quiet isolcpus=1"

$ sudo update-grub
$ sudo nano /etc/rc.local
-----------------------------------------------------
    #!/bin/sh -e
    #
    # IRQ Affinity by mozmck
    sh '/etc/irqbalance.d/lcnc_irqpolicy.sh'
    exit 0
-----------------------------------------------------
$ sudo chmod +x /etc/rc.local
$ sudo systemctl daemon-reload
$ sudo systemctl status rc-local

What's the required voodoo to verify/debug besides $ watch -n1 -d cat /proc/interrupts ? 

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10 Feb 2024 19:01 #293025 by rodw

Made this sticky, thank you.

If this is stickied now, is this the right section? It might be better in Installing linuxcnc
The following user(s) said Thank You: seuchato

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10 Feb 2024 19:16 #293026 by Mecanix

I haven't tested it myself yet, but I know I have a dual-core or two around here that I can try it on. Probably be next week or so before I can find time to do that.
 

(my take:) I wouldn't bother spending time on those expired dual-core dinosaurs, @mozmck. As soon as you "isolcpus=1" this in grub you instantly lose irqbalance. The service won't even start regardless if the script is ran from a policy or by using rc.local custom/adapted script from rc.local. 

One thing for sure, this hack works flawlessly for =>4 cores cpus. Remarkable enhancement I'd like to add. Recommend!!! 
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10 Feb 2024 19:53 #293033 by tommylight

If this is stickied now, is this the right section? It might be better in Installing linuxcnc

That or "driver boards", what would be more appropriate?

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10 Feb 2024 20:37 #293035 by cmorley
Should probably be added to official docs..
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11 Feb 2024 01:20 - 29 Feb 2024 21:11 #293049 by mozmck
Here is a script which will do the following:
  1. Set up isolcpus and a couple of other kernel arguments
  2. Run update-grub
  3. Create the IRQ affinity policy script for irqbalance
  4. Set up irqbalance to use the script.

There are a few kernel options that *might* be helpful in reducing latency that can be enabled by uncommenting the relevant sections.
There are a couple of lines at the end which disable syncing the system clock to internet time servers.  This syncing has in the past been one cause of realtime errors.  This might should be made default???

To use, save the script as "rt_setup", make it executable, and run it with sudo because it needs root privileges.
sudo ./rt_setup
Then you'll need to reboot the PC.

One improvement would be to detect dual-core systems or ones without irqbalance and do something different for the IRQ affinity.

****** UPDATE ******
I updated this script and moved it to the first post in this thread.
Last edit: 29 Feb 2024 21:11 by mozmck.
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13 Feb 2024 21:13 #293261 by Ekholm
 
I got the error in the picture. can't find folder
Attachments:

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13 Feb 2024 21:22 #293264 by Mecanix

I got the error in the picture. can't find folder

$ sudo apt update && sudo apt upgrade
$ sudo apt install irqbalance
$ sudo ./rt_setup
​​​​​​​
 
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13 Feb 2024 21:49 - 13 Feb 2024 21:55 #293267 by mozmck
Is irqbalance installed? - Oops, should have refreshed the page before sending.  I don't know where else the config file for irqbalance would be than /etc/default
What linux distribution are you running?
Last edit: 13 Feb 2024 21:55 by mozmck.

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14 Feb 2024 04:36 #293295 by hmnijp

Something like this should work:

#!/bin/bash
MASK=$( printf "%X" $((1<<`lscpu -e=CPU | tail -1`)) )
NIC=`awk 'BEGIN{nic=""} {if ($1=="iface") {tmpnic = $2} if ($1=="address") {if ($2 == 10.10.10.1) {nic = tmpnic}}} END{print(nic)}' /etc/network/interfaces`

if [ "$NIC" != "" ]; then
    grep $NIC /proc/interrupts | cut -d ":" -f 1 | while read -r IRQ; do
        echo $MASK > /proc/irq/$IRQ/smp_affinity
    done
fi
exit 0"
 

quotes seem to be missing here?  ($2 == 10.10.10.1) →→→ ($2 == "10.10.10.1")

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