LinuxCNC for possible use with G540/X-Carve

I'm building an X-Carve and I'm considering a Gecko G540 for a hardware motion controller, and LinuxCNC for the software.

As recommended, I downloaded the Live/Install DVD image linuxcnc-2.7-wheezy.iso, burnt it to DVD and I'm running a latency test on the machine I want to use. I'm simultaneously trying to load the machine by running several instances of glxgears, and several simultaneous YouTube videos on AutoPlay.

For some reason, the Live CD comes set up with power management and screen saver operational (which I understand would NOT be advisable for a computer controlling a CNC machine, so why?) and also, it keeps trying to do an automatic update which is pointless, seeing as it's a DVD! But anyway...

The only browser is some piece of rubbish called IceWeasel which can't run for 30 minutes without crashing. Believe me, I've had to restart that 20 times already. I'd like to run the latency test for 12 hours or even 24 hours to try and get some righteous numbers for the maximum jitter, as I understand that is key to assessing the machine's potential, and also required when actually setting up after install.

So, that's the position here, and I'd like to invite any constructive suggestions on getting a good assessment of the machine's potential. It looks good so far, but any recommendations on improving the test/getting more useful results would be appreciated.

I'm not sure you need to run the latency test for more than a few minutes, as long as you're giving the computer enough tasks to adequately load the processor and memory, it shouldn't take more than 10 minutes to get a reasonable baseline. At least for a hobby machine like an X-carve, if you were setting up a machining center and needed 3000ipm rapid moves your timings might be more critical, but you should be able to achieve 200ipm reliably with numbers that are "in the ball park."

I haven't had issues with iceweasel crashing, one of those automatic updates might be an update to address the stability issue with iceweasel. Although I haven't had issues, iceweasel still isn't my favorite web browser, you can get firefox or chromium out of the package manager, or with a bit more effort add the necessary repository and install google chrome, unfortunately every time you reboot you'll have to re-install and/or update packages, until you're sufficiently pleased with the OS that you choose to install it to a permanent drive. Installation from the package manager should only take a couple minutes, or from terminal a little less time.

I've never trusted the live OS to be 100% representative of the actual installed OS, I have run live and installed versions of several distributions of Linux and found that the default settings for things like power management and screen savers can vary slightly between the live and installed version. The default setting for the installed 2.6 version was to have the screensaver enabled as I recall. I'm not sure it was changed for 2.7, I believe the developers leave the majority of the settings at the distribution default and only add or change what is necessary for LinuxCNC to run.

From the tone of your post, I'm guessing you are not a Linux user. Any Linux distro is going to be weird and clunky coming from a PC or Mac. I understand it can be frustrating, but remember Linux is still, for the most part, an operating system created and maintained by volunteer programmers. A lot of the persistent oddities remain because everybody has the time to complain but nobody has the time (or knowledge) to fix the problem. With the help of the forum you're actually getting several times more support than what you paid for.

Thanks for your response.

Yes the X-Carve I'm building is for hobby purposes, but I'd like to make it as sound and reliable a machine as possible, which is why I am looking at LinuxCNC. Alas, I don't have the budget for a really top-notch controller, but the G540 will hopefully meet my requirements.

I was trying to run the latency test with several instances of glxgears and multiple YouTube videos, but the browser kept crashing every 15 minutes or so. This meant that the videos (which would exercise the network and the video system) was mostly not running. Every time I checked the machine, IceWeasel would have crashed again, and the jitter numbers would have got worse. I figure so long as those numbers are going UP, the test isn't over. I'm going to run the test again, with VLC playing video instead of IceWeasel.

I haven't had issues with iceweasel crashing, one of those automatic updates might be an update to address the stability issue with iceweasel. Although I haven't had issues, iceweasel still isn't my favorite web browser, you can get firefox or chromium out of the package manager, or with a bit more effort add the necessary repository and install google chrome...

I tried to install google chrome, but the install failed, probably because I'm not familiar with the package manager. I tried to let the automatic updates complete, but that failed as well, for reasons I do not know.

I will create a partition on the HD and do a full/proper install from the DVD to actual disk, and try again to assess the software from there.

From the tone of your post, I'm guessing you are not a Linux user.

Actually, I have not used Windows since 1996 and didn't use it much before then, either. The last machine I owned with Windows on it, was Windows v3.0. I basically went from DOS to OS/2. I've been running Linux for the last 20 years on machines of all shapes and sizes, and I've done hundreds -- if not thousands -- of installs via floppy, CD, DVD, network, etc. I've built headless disk, web, mail and file servers, triple-headed workstations, diskless PXE network booting firewalls... Any way, I'm not uncomfortable with Linux.

I use Slackware. My exposure to Debian on Raspberry Pi caused me to throw three RPi2 units into a box to collect cobwebs, and my 24 hours of exposure to Debian on this Live DVD actually made me consider installing Windows and trying Mach3. (And if you knew the level of distain I have for Microsoft products, your eyebrows would rise!) Since LinuxCNC seems to be a chimera (part application, part operating system) and I can't install it on Slackware, I will have to treat it like hardware. The machine will boot straight into the application, and I'll just do everything else on a Slackware box, and just drop my .nc files on a NFS filesystem for LinuxCNC to use.

Any way, I'm going to test again with different circumstances, in the hope of getting a reliable set of results.

I have an X-Carve running with a Gecko G540 under Linuxcnc.. Standard Debian with Linuxcnc 2.7.3.
Works very well indeed. Let me know if you want any config details.

Thanks for the offer. I'm in the early stages now, but I may take you up on your offer later!

Since LinuxCNC seems to be a chimera (part application, part operating system)and I can't install it on Slackware........

Linuxcnc is nothing to do with operating systems, it is an application.

The problem is that few people would have the knowledge to install and build its requirements, so it is presented as a complete distribution of which Linuxcnc forms a small part.

Most of your gripes are with Debian not Linuxcnc.

I was trying to run the latency test with several instances of glxgears and multiple YouTube videos, but the browser kept crashing every 15 minutes or so. This meant that the videos (which would exercise the network and the video system) was mostly not running. Every time I checked the machine, IceWeasel would have crashed again, and the jitter numbers would have got worse. I figure so long as those numbers are going UP, the test isn't over. I'm going to run the test again, with VLC playing video instead of IceWeasel.

You need to test what the computer is going to do.
Running multiple instances of glxgears imposes a load from openGL usage, moving windows rapidly or cycling between them forces redraws and tests the video system.

No-one can watch more than one video at a time and hopefully you are not going to watch anything at all whilst machining, so this running videos through a browser is completely unnecessary. I know it is recommended in places, but to my mind it is completely specious.

I figure so long as those numbers are going UP, the test isn't over. I'm going to run the test again, with VLC playing video instead of IceWeasel.

The numbers can only ever go up, which is another problem of the latency-test.
It is a cumulative total and often a never repeated spike right at the start due to disk access and other system resource hits will colour the whole test.

Run it for a couple of minutes and then reset. Then run real world tests for things you are likely to do whilst running a machine, eg switch workspaces, switch windows, do some file transfers, move the mouse, plus the underlying openGL load from about 4 - 6 instances of glxgears.

As previously mentioned, your results will be subject to the access times imposed by running from a removable medium and will probably not be as good as an installed version.
Should give you an idea though.

regards

Most of your gripes are with Debian not Linuxcnc.

I know. I haven't seen LinuxCNC running, yet.

Run it for a couple of minutes and then reset. Then run real world tests for things you are likely to do whilst running a machine, eg switch workspaces, switch windows, do some file transfers, move the mouse, plus the underlying openGL load from about 4 - 6 instances of glxgears.

I've installed it on the disk, and I'll try a short test as you describe.

Thanks for your comments and suggestions.

No-one can watch more than one video at a time and hopefully you are not going to watch anything at all whilst machining, so this running videos through a browser is completely unnecessary. I know it is recommended in places, but to my mind it is completely specious.

Then run real world tests for things you are likely to do whilst running a machine

Could not agree more.

Rick G

The busiest my machine has ever been was when running latency-test!
While I do copy files over my network to and from the computer,that's never done while I'm actually machining something.
The only time that the specifics of the operating system got in the way was setting up some menus and panel layouts I wanted and that was because most of my Linux work over the years has been with Redhat/Centos not Debian.

I figure the only time I'll be doing any sort of upgrade will be to install a new version of Linuxcnc (or perhaps PathPilot...)