[ale] Linux vs XP Embedded

[Bjorn Dittmer-Roche]

I'm no expert but I've done a bit of research on the topic. If you are not
doing serious real-time, either OS should be fine as far as scheduling.
You can expect simmilar performance and latency out of them and you'll
have to actually do benchmarking to determine which performs better with
the hardware in question. Linux is a joy to program and some people really
like to program windows, too, so I would make that decision based on the
experience/preferance of the admins/programmers and, ahem, the need for
reliability.

FreeBSD is another great option for high performance/small footprint/no
charge. It's got great threading and very good latency and linux binary
comatibility which, in amny cases, outperforms "real" Linux.

If XP/Linux 2.6/FreeBSD won't cut it in the scheduling department, you
need something more serious. You can't do better than QNX. QNX is really
quite increadible. It's posix compliant, real-time, well supported and if
you need to write your own drivers for anything, it will take much less
time in QNX than anything else because the drivers run in protected
memory space.

The "real-time"  versions of linux don't use the same userland API's as
normal processes, so I'm told that as a result they are difficult to
program and have some annoying restrictions, so I would stay away from
that.

	bjorn

On Tue, 24 Feb 2004, Joe Knapka wrote:

> Hi folks,
>
> I've been given an interesting realtime control system to build, and
> my employer wants to evaluate both Linux (woohoo!) and Windows XP
> Embedded (bummer).  I know some of you have some embedded/realtime
> experience with Linux, so I'd like your opinions on this subject.  I
> can't say much about the application itself, except that it will be
> handling something in the neighborhood of 50Gbytes per day (that's a
> G) of IP and serial traffic, and must meet hard deadlines on the order
> of once per second (but a missed deadline won't kill anyone - this is
> not a medical or aviation application. We can probably even recover
> from a missed deadline, but that sort of thing should be kept to an
> absolute minimum).
>
> I'm thinking that a 2.6-series kernel would be the way to go with
> this.  I understand 2.6 integrates the preemptive and low-latency
> patches, and that 2.6 can be built in a VM-less configuration so as to
> remove latency associated with demand paging.
>
> Does anyone have any further suggestions or alternatives?  Also, is
> anyone here in a position to evaluate the relative strengths of Linux
> vs XP Embedded?  Personally I feel that the "Embedded" part of that
> name is probably pure marketing hype, but I could be wrong.  It is hard
> to see how Linux could possibly be a *worse* choice then XP in this
> domain, though.
>
> Thanks,
>
> -- Joe Knapka
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