Latency over 15.000.000 - before it was between 6000 and 7500

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15 Sep 2017 10:56 #98990 by denhen89
Hello guys,
i really need your help as soon as possible, because right now i am very frustrated with LinuxCNC. I am sorry for the long story, but i think i should explain everything.

Some time ago i got an modern PC from my brother without an VGA. That PC has an ASUS M4A88TD-V EVO/USB3 motherboard, AMD Phenom X6 CPU, 64gb ram (in bios it shows only 16gb, dont know why?), 64GB SSD.
To be abtle to install LinuxCNC and do an Latency test, i put in the VGA (GTX 770) form my main PC.

The Latency test result:
Max Jitter(ns) 1.0 ms thread: about 6000
Max Jitter (25 us thread) : about 7500

I was so happy to get such good result, so i moved on to install the 2.8 Pre Master version, and after some time i also got it o work. If i remember correctly i was fighting to get the 2.8 Version downloaded and installed, but when i opened LinuxCNC it still showed the version 2.7 (i think it was this version), so i had to disable it and activate 2.8. I really dont remember anymore if that was exactly what i did but this is what i remember :D.

After the update was done i did not check the Latency anymore, i shut down the PC, took all wires off and put the PC in the corner.

Yesterday i bought an used GTX 770 card, because i knew it works with that card and also i wanted to use this PC for Solidworks.
I have put in the new (used, but working) VGA, started the PC for the first time after about 3 month and straight got into problems:
When loading Linux i got some error messages. /sbin/modprobe -b pci... Please take a look the picture in attachment.

So, i thought maybe that VGA does not work, so took it out and put in my VGA which i used 3 month ago and got the good latency results. I still got the same message, but not always, so i played around with the bios settings. Disabled CI1 and some other stuff.
Later i got it done and now Linux is (mostly) starting without problems, but the Latency test is.... EXTREMLY BAD. Starts with over 9.000.000 and after some time it goes up to 15.000.000.
I had many updates to do, so i have updated all, but that did n ot changed anything.

I then thought that maybe there is no VGA driver installed ?? So i tryed to figure it out, by googling and find the correct commands.
I tryed so many that i dont remember them, but that commands was to check what VGA is installed and showed GTX 770. Then i tryed some commands to check if any drivers are installed. It gave some output, but only 2 lines and nowhere i found "Nvidia", "nouveau" or "vesa" (i think that are all possible drivers for nvidia VGAs?), so i thought that the VGA driver got somehow erased, and tryed to install nvidia driver and nouveau, but i did not get it done.

In the synaptic packet manager is found files named Nvidia, so i dont know right now if there are drivers installed or not.

After couple hours of trying i was soo frustrated, because of this all problems and LinuxCNC. Like on the first time i installed Linux i alsohad again problems with the Clock and i couldnt anymore find the commands to solve that problem. Then also all the time some dpkg/lock problem, which i somehow got deleted (but the file showed again in the folder after entering an new command). Then i also foudn out that i have no GLXgears..

It was late in the night, so i googled a bit and found here an thread where someone wrote that with the 2.7 Version he has Latency of about 15.000, but when using 2.8 its over 1.000.000.
So, is 2.8 pre the problem here ? I just tried to deactivate the 2.8 version and activate 2.7, but i dont know anymore how it works.

Why the hell everything on LinuxCNc has to be so complicated...

I am now already thinking to not work with Linux and just use Mach3, because if 2.8 version dont work like it should, then i cant use the square gantry feature with 2 home switches.

Guys, i am really sorry for crying here around about LinuxCNC and also the long text, but if there is any fix for my problem, then please let me know it. I wanted already to reinstall LinuxCNC, but could you tell me how to test the Latency with the 2.7 version and if the latency is good then 2.8 is the problem and will delete Linux and install Windows and use Mach3. I think there is no other alternative then, because i want to have the square gantry feature with 2 motors and mach3 has it.

Thanks in advance.

Br,
Denis
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15 Sep 2017 13:01 #98993 by PCW
I dont think that this is a 2.7 versus 2.8 issue

On your current system can you post the results of:
uname -a

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15 Sep 2017 13:08 #98994 by denhen89
Thank you for your reply PCW.
As soon as i get back home (in about 1 hours) i will post the result.

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15 Sep 2017 13:59 #98996 by denhen89
So, that is the result:
xxxxx@DENISCNC:~$ uname -a
Linux DENISCNC 3.4-9-rtai-686-pae #1 SMP PREEMPT Debian 3.4.55-4linuxcnc i686 GNU/Linux

Thanks in advance.

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15 Sep 2017 20:02 #99007 by PCW
OK so you are at least running a real time RTAI kernel

Usually really bad latency is due to:

1. CPU power management/clock speed switching/C states (Cool&Quiet etc) enabled in BIOS
2. Hardware with bad drivers, Nvidia is an example of this
3. Failing hardware (check you dmesg for evidence of this)
4. Systems where you cannot disable power management (Laptops commonly)

I run 2.7 and 2.8 on many test systems and have not seen any difference in latency
I suspect something happened to your PC to change latency not related to LinucCNC version

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16 Sep 2017 00:20 #99017 by denhen89
Hello,

again thanks for your reply and help.

So, i have some good news (i think...).

After playing around with the bios settings with no good results and also trying to install vga drivers without success, i deciced to delete LinuxCNC by installing Windows 7 ULT. I used Windows 7 to deinstall linux, because i read it should be installed before LinuxCNC to prevent the erasing of the GRUB, and i wanted to use Windows 7 for Solidworks/Solidcam or other alternative progs, so i think it was the quickest way to deinstall LinuxCNC.

After windows 7 was installed i put in the USB stick with LinuxCNC Wheezy 2.7 and decided to first try the LiveCD before installing and do the Latency test with GLXGEARS and using the browser to write this post :).

Result after 30mins:
Max Interval (Servo thread 1.0 ms) 1005743
Max Interval (Base thread 25 us) 30351
Max Jitter (Servo thread 1.0 ms) 7423
Max Jitter (Base thread 25 us) 6996

So, it looks like everything works good. I got the same result as 3 month ago, but 3 month ago LinuxCNC was installed and not running from LiveCD, so if fear that if i will install it and update everything include the update to 2.8 Pre, that i will again have Latency problems. The good thing is, that i now know that my Hardware is fine.

Today (after i got some sleep) i will install LinuxCNC, update to 2.8 pre and do the Latency test again. If everything will work then i go to pick an second SSD just for LinuxCNC, because right now i have only an 64gb SSD (55gb netto) and Windows 7 with VGA and ethernet driver takes about 42GB, so no space for Solidworks and Solidcam or other alternative progs. I will then format again and use the 64gb just for LinuxCNC.

I hope that LinuxCNC 2.8 pre will work.

I will inform about the results then.

Good night/day. :)
Br,
Denis

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16 Sep 2017 10:42 - 16 Sep 2017 10:43 #99028 by denhen89
Hello,

i try to keep it as short as possible. (after updating to 2.8 pre the latency was again over 10.000.000)

1. LinuxCNC Wheezy 2.7 install
- Installed
- Tested Latency :
- Result:
Max Jitter (Servo thread 1.0 ms) 7423
Max Jitter (Base thread 25 us) 6996

2. Available updates
- Updated all available updates
- Tested Latency :
- Result: Same (everything works fine)
- Rebooted

3. Updated to 2.8 Pre (how i did it)
- opened Synaptic Packet Manager
- Settings → Repositories → "Other Software" Tab
- unchecked all links related to LinuxCNC
- added this 2 lines:
deb buildbot.linuxcnc.org/ wheezy master-sim
deb-src buildbot.linuxcnc.org/ wheezy master-sim
- closed the window and reload updates
- updated
- rebooted

4. Problems started now
4.1 - (see picture "1.jpg") PC started and the Motherboard information screen which shows what to press for what (bios, boot menu, etc.), showed for about 20-25 seconds, but usually its just there for 2-3 seconds.
4.2 - (see picture "2.jpg") GRUB Menu loaded, but now after the update i had 2 Linux versions to choose
4.3 - I choosed the first option (3.4.9) like you see on the picture
4.4 - (see picture "3.jpg") - When loading Linux it took quite long and showed some USB error. There cam 2-3 more USB errors and all where about same, but not all are on the pictures and after some time Linux was loaded, but i could not use my keyboard and also not my mouse, so i restarted, plugged keyboard and mouse to an different slot and changed an USB BIOS setting from "USB HiSpeed" to "USB FullSpeed or so.." (maybe not important), and then my keyboard and mouse worked, but still the motherboard loading screen was showing for 20 seconds and also loading into Linux after GRUB took very long and with some USB errors.
4.5 - Tested Latency: Result: VERY BAD (again over 10.000.000)
4.6 - (see picture "4.jpg") Restarted the PC and choosed the other Linux version (3.2.0-4-rt-686-pae): MODPROBE -b -pci ERROR
4.7 - (see picture "5.jpg") Restarted the PC again, choosed the first Linux version again, opened Synaptic Packet Manager" and searched for "Linux-image". I right clicked on an installed 3.2.0-4 and clicked "Mark for complete removal" (unfortunately the line is not visible on the picture, because i did the picture after i deinstalled the version already)
4.8 - Restarted the PC: Now everything loaded quickly like usually and GRUB does not show anymore the 3.2.0-4-rt-686-pae version.
4.9 Latency Test: still SAME BAD (over 10.000.000)

So, now its 100% that the Latency problem is produced by some update which was available after adding the 2 lines (deb buildbot.linuxcnc.org/ wheezy master-sim
deb-src buildbot.linuxcnc.org/ wheezy master-sim)

and update all available updates include the update to LinuxCNC 2.8 pre. (there wasnt so many updates, about 10-15 maybe)

Now, the next thing i would do is to reinstall LinuxCNC again, and then when adding the 2 lines to update to 2.8 pre, i will choose only Linux 2.8 Pre update, but leave all other updates unchecked.
I somehow cant believe that it has something to do with 2.8 pre, but with the other available updates.

Unfortunately i have to go away now for 3-4 hours, but when i come back home and get no other solution, then i will see how to reinstall linuxcnc easily and try to update only 2.8 without any other updates after adding the 2 lines.

PS: After adding the 2 lines and reload available updates, i will make an picture of all available updates, and post them here. Maybe someone will now what causes the latency problem if its not the 2.8 Pre version.

Thanks in advance.
Br,
Denis
Last edit: 16 Sep 2017 10:43 by denhen89.

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16 Sep 2017 11:09 #99029 by PCW
I would not expect any different since you loaded a sim = simulation package with no real time abilities

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16 Sep 2017 11:15 #99030 by denhen89
Hello,

could you tell me what you exactly mean. What did i wrong and how can i solve the problem ?

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16 Sep 2017 11:59 #99032 by denhen89
I am currently driving on the road(stopped now to write this post :D), but have googled it and now i know that the simulation package is just to play aroubd with some gcode or so but not to test the latency.
My question is now what i did wrong. Why i have that sim package. Before i updated the latency was fine, so what i have to do to get not the sim package?

Thanks in advance.

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