PREEMPT_RT patch and Arch

Question

Hello All,
I'm wondering if anyone has toyed around with the PREEMPT_RT patch using the Arch concept to simplify the processes to accommodate non-critical motion control across wireless or local area networks as a server for applications such as security cameras, thresholds, landscape automation, environmental controls, etc. There are also several commercial applications that might be reasonably run through the hybrid RT capabilities of a adapted timer and a preempted Linux kernel with an ultra-lean Arch config.
I'm a newbie and interested in finding out what I don't know before I throw a bunch of time at a flawed concept. I've been linux lurking for quite a while hoping to find a really lean operating system and overhead that retains the dual characteristics of general motion control and networking. These could be used in any number of closed loop commutation and synchronization schemes to afford relatively accurate positioning at long distances and communicate the result.
Obviously this could be accomplished with enough money to buy gear and canned (black box) applications but the cost of repetitive installation pales even the bravest entrepreneur. So, the search continues.
Is there any inherent reason that Arch and the RT patched kernel won't work together? Most of the pengutronic stuff I've been reading is a little dated. Admittedly, I may have just outed my lengthy lurk in a spasm of sheer excitement that this may be the one. But I thought I might just simply ask before I work my way to another dead end.
Anyone?

Answer 1

Let me say up front...    personally I have no idea. You could always simply try it and see if it works!
That said, my reason for posting is to say, you might get better traffic on this question in another part of the forum, since this has very little to do with differing architectures. Your best bet might actually be the Networking, Server, and Protection area since your basically talking about setting up a server designed to control security cameras, or the Kernel & Hardware Issues area, since you are asking specifically about a kernel patch.
I got curious and googled the patch you're talking about...   I am fairly sure it should work for Arch, since it seems to be very distro agnostic.
I am curious about why you feel the rt patch would help with motion control over a network...   it is aimed at working with microsecond timings, than longer term workloads. RT is only really useful (right now) for really short units of work in response to real time events. Basically, if you want to hit a bug's wing that was spotted on a camera with a high powered, very narrow focused laser, then an RT kernel might help you. An RT kernel is aimed at starting up responses really fast. Unless you are responding to something captured by the cameras, and less than a tenth of a millisecond is necessary to that response, a normal "real-fast" kernel might be a better idea.
http://www.rdrop.com/users/paulmck/real … 06.22a.pdf
There is a link to a white paper about the RT-Kernel and the Preempt_RT patch set. It's 9 PDF pages, but if you want to just skim it, the summery has a nice decision tree to help make the choice between real-time patch and the vanilla "real fast" kernel.
The RT-patchset might actually be more work than strictly needed for the concept you're working on.
It seems to me, and I am far from a Guru or an expert, that what you are hunting for is a motion capture application that can easily be network controlled and is open-source. You need a low overhead OS to give all of the system resources to the motion capturing program. Arch is good for low overhead, and there is the package zoneminder in the AUR (Also with the zmviewer-svn that adds a client capacity to the suite, meaning you can look at/control them from another computer).
You may want to look at Linux-From-Scratch to make an absolutely basic system on the hardware you wish to use for this enterprise. You can strip out all of the unneeded drivers from the kernel, locales, manpages, build tools, and all of the other cruft that is needed by the average install of any Linux OS meant to run on diverse groups of hardware.
By the way, the Linux-From-Scratch would allow you to custom compile and thoroughly test each update before sending them out as binaries to your customers, as well as allowing you to do complete upgrades rather than piecemeal updates to each program on the system as they come available. (Business like the set time table for releases because of the lower amount of downtime for the critical systems.)
Last edited by LeoSolaris (2009-05-11 14:49:41)