Re: preempt rt in commercial use

[Nivedita Singhvi <niv@us.ibm.com>]

Klaas van Gend wrote:
> On Wednesday 15 September 2010 05:38:49 jordan wrote:
>> Which leads me to my last example. Most people are aware that since
>> about 1999-2000, Linux has dominated the movie industry. Beginning
>> with Titanic and even today with say, Avatar.
>>
>> I would be willing to bet, that all of those wonderful rendering farms
>> and production suites, are
>> in fact using rt-linux.
> 
> 
> Please put a lot of money on that bet, because I'd like to win it :-)
> 
> Why would those rendering farms use rt-linux?
> 
> Rendering is not done in real-time - far from it actually. It can take minutes 
> of the entire farm to render a single frame. So rendering is nothing but CPU-
> intensive (calculating how all those lightbeams are reflected by each surface) 
> - and everything I/O bound is about throughput: writing the rendered pixels to 
> disk and getting more surfaces from disk.
> 
> There are no deadlines for rendering, there are no penalties if a frame is 
> late by seconds - if the farm cannot complete its job overnight, they'll add 
> more CPU power.

While all of the above is true, I'll add that it's worth testing
RT because certain applications which have lock-step operations,
can be very negatively impacted in throughput by severe lack of
determinism.  If all of a set of operations need to complete before
they can do the next set of operations, and one of the threads takes
very long, the others all idle as a result. If this happens frequently,
you're better off trying to cap max latencies.

So RT actually provides improved *throughput* as well, despite the
increased overhead.

I don't know if these rendering type applications necessarily
fall into that bucket, but I would at least take a look.


thanks,
Nivedita