Script for automated testing of computer latency.

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01 Oct 2020 08:00 #184459 by seuchato
Get well soon! Thanks.
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02 Oct 2020 17:28 #184590 by tommylight
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11 Oct 2020 18:44 #185742 by seuchato
BeagleBrainz pointed out , that for a latency test "one should stress the computer". This is also mentioned here . BeagleBrainz stated also, that this means io load, like disc access, like opying large files around etc.

So far, my script does none of this. It collects data of the hardware used and invokes a latency test with or without a base thread, depending users wish and/or if a parallel port is detected.

While I did exactly that (ripping a dvd to hd) for wheezy based install, I did not consider this being required to get "realistic" latency data when writing the script. It was my believe, that LnuxCNC, once loaded from disc, does by far most of its duties in Ram. It would read the gcode file yes, but these files almost never go into the GB range. The largest gcode file I have is ~22MB.

Prior to adding heavy disc io, I would like to understand the reasoning, as why this is really needed to get reliable, repeatable latency data for the - say - database in https://forum.linuxcnc.org/18-computer/39371-results-of-latency-test-list-of-computers-tested-for-use-with-linuxcncthis thread.

So, kindly give me a hand, let me know why it is needed and - most important - what is needed.

Greez
chris

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11 Oct 2020 19:43 #185747 by BeagleBrainz
Quoting from the docs. Emphasis by myself.

"The idea is to put the PC through its paces while the latency test checks to see what the worst case numbers are."

To me that would mean not to simulate a Linuxcnc session but to really put a heavy load on the computer. Similar to destructive testing of a product.

I guess you could create a file, write a certain amount of bytes from /dev/random, move the file around, delete the file, create another larger file, do the same, create a number of smaller files using the same method, move them around. Open a few random windows, move them around, close them.
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11 Oct 2020 21:53 #185764 by tommylight
DD is very useful for that as it can be used to write zeros to HDD/SSD or read from them and write to nothing:
www.cyberciti.biz/faq/howto-linux-unix-t...nce-with-dd-command/
That is just one of many examples.
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15 Oct 2020 19:45 #186227 by seuchato
@beaglebrainz: thanks for the hint. I will add io load.
@tommylight: thanks for the link, inspiring. Tomorrow I got off for the weekend. Apart from stripping weight off our FP2NC to hopefully get ot down to our workshop, I have nothing to do. Soooo, I'll probably be working on the script again.

Greez
chris
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16 Oct 2020 06:25 #186254 by seuchato
help needed:

Can someone that has no separate /home partition kindly post the result of:
mount | grep -Ei "on /home"

Tia
chris

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16 Oct 2020 07:23 #186256 by BeagleBrainz
rmurphy@thinkPad-t530:~$ mount | grep -Ei "/home"
rmurphy@thinkPad-t530:~$
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16 Oct 2020 07:32 - 16 Oct 2020 07:33 #186258 by seuchato
BB (or however else :) )
can you kindly also post the result of this:

lsblk -b -o MOUNTPOINT,FSAVAIL -x FSAVAIL | grep "/" | awk '!seen[$0]++' | sort -r -n -k2 | sed -n 1p

Tia
chris
Last edit: 16 Oct 2020 07:33 by seuchato.

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16 Oct 2020 07:48 #186260 by BeagleBrainz
rmurphy@thinkPad-t530:~$ lsblk --version
lsblk from util-linux 2.31.1
rmurphy@thinkPad-t530:~$ 
rmurphy@thinkPad-t530:~$ lsblk -b -o MOUNTPOINT,FSAVAIL -x FSAVAIL | grep "/" | awk '!seen[$0]++' | sort -r -n -k2 | sed -n 1p
lsblk: unknown column: FSAVAIL
Try 'lsblk --help' for more information.
rmurphy@thinkPad-t530:~$ 
rmurphy@thinkPad-t530:~$ lsblk -b -o MOUNTPOINT,FSTYPE -x FSTYPE | grep "/" | awk '!seen[$0]++' | sort -r -n -k2 | sed -n 1p
/          ext4
rmurphy@thinkPad-t530:~$ 
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