On Sat, 2012-03-31 at 08:00 +0200, Alwyn McLeod wrote:
> When I run the latency test, I get Base thread jitter of 932659. In the
> config file the max. is set at 50,000.
>
> When I load EMC2 I get a message "Unexpected real time delay: check dmesg
> for details' as well " RTAPI: ERROR:Unexpected realtime delay on task 1.
> This message will only display once per session. Run latency test and
> resolve before continuing.
>
> Being a novice as far as Ubuntu is concerned, I am at a loss as to how I
> can resolve these issues. Any assistance will be appreciated.
The jitter you measured is too high, so you'll need to make some
configuration changes to make it better. If your PC where sitting in
front of me, I would first check on what slots it has, the processor
type and chipset, what video port is being used as well as the monitor.
This would give me an idea of what changes can be made to keep the video
system from interfering with latency. Also I would watch the latency
test for a while to see when the really bad numbers come up. If the
numbers jump right a way, my guess is the video driver, if some event
like a disk access or plugging in or accessing a USB device, maybe a
related BIOS setting may be needed. If it happens and repeats after a
couple of minutes, it might be the SMI issue mentioned in the trouble
shooting section on the wiki. When the latency numbers start getting
pretty good from the changes you have made, it would be best to run the
test over night to make sure something else that operates on a long time
base doesn't slip through.
Without knowing all of the above, my most common solution tends to be
getting the xorg.conf file settings to work. On a new install, this file
doesn't exist. So one will need to be made. If you have an xorg.conf
file, make a copy of it so you can reuse it if needed.
I usually start a terminal window (from the Desktop; Applications /
Accessories / Terminal), type on the command line "sudo
gedit /etc/X11/xorg.conf". This will give you root privileges so you can
edit a system file, then gEdit will create the new file and you can fill
in what is needed. Usually I add something similar to:
~~~~~~~~~~~~~
Section "Device"
Identifier "Configured Video Device"
# Driver "nvidia"
Driver "vesa"
EndSection
Section "Monitor"
Identifier "Configured Monitor"
Option "DPMS"
Horizsync 30-66
Vertrefresh 50-130
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
Defaultdepth 24
SubSection "Display"
Viewport 0 0
Depth 24
Modes "1280x1024"
EndSubSection
EndSection
Section "ServerLayout"
Identifier "Default Layout"
screen "Default Screen"
EndSection
~~~~~~~~~~~~~~
The # comments out the current video driver if this line exists, then I
load a generic driver (vesa) that plays well with latency. Sometimes
there is an open source version of a proprietary driver, which can work
well and have more features than vesa.
The monitor section lets the computer know what frequencies and
resolutions are valid for the monitor. My equipment tends to be very old
and Xorg has a hard time getting the settings on its own. One thing I do
first is to bring up System / Preferences / Monitors and see if the
monitor is recognized and the proper resolutions listed. If not, I add
the Monitor and Screen sections to xorg.conf. If you add the monitor
data, it is very important you use the actual data that matches the
make, model and version of your monitor. Setting these wrong can make
you monitor unreadable or go blank, and for a Linux novice can be very
hard to get out of gracefully. By the way, if this happens, Alt F1 may
get you to a terminal session. If Xorg does get some of these settings
correctly, then you can leave those parts out. Getting this sorted out
can take hours and a lot of rebooting. Oh, and when you save the new
settings, just log out and back in (use the power icon and log out
instead of power off) in order to activate the new settings or reboot.
If the latency problem is not video related, you may need to study the
troubleshooting and related sections in the wiki and other
documentation.
Don't be afraid to ask questions, good luck.
--
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA
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