On Fri, 8 Jan 2021 09:27:35 +0000
Ahem A Rivet's Shot  wrote:

>On Fri, 08 Jan 2021 09:56:13 +0100
>Deloptes  wrote:
>
>> I know a guy from the mailing lists (Gene Hasket) that is operating some
>> CNC and was complaining about lack of RT in linux. He is using some
>> patched kernel from somewhere - I do not recall the details, but it is
>> really a problem that Linux is not applicable to time sensitive
>> applications.

Well, some 10 years ago, the firm I used to work for designed a print register
control system running on Linux retrofitted to a printing press. This was a
press that spilt the printed sheet into four ribbons, lined them up one on top
of the other, and also timed the cut and fold. I was there the first time it
was
run. A gaggle of bigwigs were there, and as the press operator started the
machine one of them asked when it would be in register. By the time the
printing
itself was stable, and they picked up one of the folded sheets, it was in
register on all four sheets within 2mm.

Fun facts:
The machine had rated top speed of 36,000 copies per hour - 10 A3 size per
second. On an emulated press, our system could manage at least 60,000. Modern
presses do 100,000

> Problem ? It's a fact and always will be that multi-tasking
>operating systems and real time processing don't go together unless the
>real time demands are very long relative to the processing speed (eg.
>payroll).
>
> Time was we used MS-DOS for burning CDs rather than unix because
>it only took one late write to make a coaster, buffering and faster
>processors means that we can now burn blu-ray discs from a multi-tasking OS
>and almost never make a coaster. That doesn't make unix a real time OS it
>just means that the timescales have shrunk.
>

Even on an old eeePC900 by adjusting the priorities I can see the audio and
interface threads are running on different cores, so with modern high count CPU
cores, and GPUs the distinction is becoming moot. I don't know how to do it
myself, but a *lot* of audio processing is very simple parallel operations -
the thing that GPUs excel at!

--
W J G

--- SoupGate-Win32 v1.05