From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nivedita Singhvi Subject: Re: preempt rt in commercial use Date: Wed, 15 Sep 2010 07:03:17 -0700 Message-ID: <4C90D225.1080902@us.ibm.com> References: <201009151059.23039.klaas.van.gend@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: jordan , Raz , linux-rt-users To: Klaas van Gend Return-path: Received: from e3.ny.us.ibm.com ([32.97.182.143]:48669 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218Ab0IOOEJ (ORCPT ); Wed, 15 Sep 2010 10:04:09 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e3.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id o8FDmEV4027576 for ; Wed, 15 Sep 2010 09:48:14 -0400 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o8FE46bJ046432 for ; Wed, 15 Sep 2010 10:04:06 -0400 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id o8FE45vA025603 for ; Wed, 15 Sep 2010 08:04:05 -0600 In-Reply-To: <201009151059.23039.klaas.van.gend@mvista.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: 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