RPI4 Raspbian 64 bit & LinuxCNC

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11 Apr 2021 01:44 #205597 by cakeslob
works on 8gb, the 5.10 atleast , but im getting constant low voltage warnings which are (presumable) causing intense latency spikes, works pretty good on cm4 2gb
The following user(s) said Thank You: elovalvo

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20 Apr 2021 05:05 #206501 by tjtr33
i think there are too many closely related threads here

and this hread is about rpi 64 bit so i post again...

elovalvo's 64bit runs well on pi4 4g
aarch64 5.4.61-rt37-v8+ 2.8.1
30.2 max base latency after 14 hrs
latency-histogram --base 80000 --servo 1000000
with 4 glxgears
hth
tomp

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21 Apr 2021 05:25 #206615 by tjtr33
Another 14 hr run gave me 25.8 max base latency.
I use
latency-histogram --base 80000 --servo 1000000
with boot params of
isolcpus=1,2,3 idle=poll
and disable the screen blanking & screensaver

I dont know why 80 uS base period is such a sweet spot,
but 50,60,70,90 and 100uS were all tested. ( many tmes on may pi's )
and all (non-80) were not as good.
Why is 80 'sweet'?

I did get pretty good resuts from 50uS base period,
seeing 34uS latency after just a couple hours.

I was ready to discard the 50uS as a possible based thread period,
but it leaves 16 uS.

I say this ("leaves 16uS") because I believe the period - latency = reliable time available.
Is that true?

Then...
how good is 16uS as a time to get everything done?

When people say that 20uS latency is good in the context of a 50uS thread period,
are they implying they need 30uS to accomplish all tasks?

Is there a profiler that can determine how much of the period is used/unused?

thx
TomP
tjtr33
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21 Apr 2021 22:44 #206729 by andypugh

Why is 80 'sweet'?


I suspect that you are closer to knowing that than anyone on the planet. At least you know it.
The number of realtime users on the Pi in the world who have analysed the system is measured in the "severals" I suspect.

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22 Apr 2021 03:37 - 22 Apr 2021 03:38 #206760 by tjtr33
Thx Andy :-)
also
i ran a 50uS base thread ( still running)
and have max latency 28.7
i did change the environment in that i setup Samco's suggested ntp fix.
lateny-histogram --base 50000 --servo 1000000, with 4 glxgears
isolcpus=1,2,3 idle=poll
over 17hrs now
tjtr33
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Last edit: 22 Apr 2021 03:38 by tjtr33.

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04 May 2021 19:30 #207865 by Craig E
A total newbie I am trying to install this on a new PI 4b 8G
I get to here and it cannot find this file
git clone github.com/LinuxCNC/linuxcnc.git emc

Then I am done.
What am I doing wrong? any help is greatly appreciated

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04 May 2021 22:08 - 04 May 2021 22:09 #207883 by andypugh
Try
git clone https://github.com/LinuxCNC/linuxcnc.git linuxcnc-dev

(It might well be that the command that you copied was munged by the auto-linking feature of the forum, where did you find it? )
Last edit: 04 May 2021 22:09 by andypugh.

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05 May 2021 11:43 #207952 by Craig E
Thanks Andy,
I am following the procedure at the top of this string.
Your command worked but stopped on the next command after that. Below is the whats left for me to follow.
I am totally new to both LinuxCNC and Rpi4 but I was able to install the 64bit OS and the Real time Kernel rt64-kernel.tgz.
I am stuck on building LinuxCNC for PRI4 64 bit and installing it.
Below is where it all ended for me.


git clone github.com/LinuxCNC/linuxcnc.git emc
cd emc

debian/configure uspace
dpkg-checkbuilddeps

debuild -uc -us
cd ..

The .debs file can be also download from this link:
LinuxCNC_64bit.zip

Installing LinuxCNC:

cd ~/
wget ftp.it.debian.org/debian/pool/main/p/pyg...2_2.10.1-3_arm64.deb
sudo dpkg -i python-gtksourceview2_2.10.1-3_arm64.deb
sudo apt --fix-broken install

sudo gdebi linuxcnc-uspace_2.9.0~pre0_arm64.deb
sudo gdebi linuxcnc-uspace-dev_2.9.0~pre0_arm64.deb
sudo gdebi linuxcnc-doc-en_2.9.0~pre0_all.deb

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05 May 2021 13:24 #207965 by elovalvo
If you followed Andy's command, the following command must move you to a new directory called 'linuxcnc-dev'

So the 'cd emc' command becomes 'cd linuxcnc-dev'

Also be careful that the command
wget ftp.it.debian.org/debian/pool/main/p/pyg...2_2.10.1-3_arm64.deb

will have to be fully extended to

wget ftp.it.debian.org/debian/pool/main/p/python-gtksourceview2_2.10.1-3_arm64.deb

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05 May 2021 13:55 #207967 by Craig E
Thanks that worked but now I am getting this error

dpkg-checkbuilddeps
dpkg-checkbuilddeps: error: Unmet build dependencies: debhelper (>= 6) libudev-dev tcl8.6-dev tk8.6-dev libreadline-gplv2-dev asciidoc (>= 8.5) dblatex (>= 0.2.12) docbook-xsl dvipng ghostscript graphviz groff imagemagick inkscape python-lxml source-highlight w3c-linkchecker xsltproc texlive-extra-utils texlive-font-utils texlive-fonts-recommended asciidoc-dblatex libxmu-dev libglu1-mesa-dev libgl1-mesa-dev | libgl1-mesa-swx11-dev libgtk2.0-dev intltool autoconf libboost-python-dev netcat libtirpc-dev

I am assuming that these did not load correctly up in the build Phase I did get some files not found notes but no errors that I can remember

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