From: Dirk Baerts (d.baerts++at++fokkerspace.nl)
Date: 11/15/2000 06:41:27
Allan,
Thanks for your extensive answer.
Unfortunately, one chef whipping the eggs isn't an option right now.
And indeed, the O2 is short of system memory : 64 M. We'll do something about
that.
Dirk
> On Nov 14, 6:05pm, Dirk Baerts wrote:
> > We developed a pf app for an Onyx2, that - as an option - uses a Pbuf
> > and noticed that when this option is on, another pf app running on the
> > same machine suffers a dramatic performance hit.
> > The first app has a very small scene : one cube, three cylinders,
> > implemented in OpenGL and Performer, no special effects
> > The second has a rather large scene, build on VEGA & Performer, with
> > special effects.
> > Both running 20 Hz. And sharing pipes.
> > Before bothering you with details :
> > -- Is there a general rule to run several pf apps concurrent on the same
> > machine ?
>
> Yes: don't. Running multiple _independent_ Performer applications on
> one system is akin to multiple chefs trying to whip eggs in the same
> bowl. They spend more time disentagling from each other than making
> the dish.
>
> To be more precise, each DRAW process will be competing for access to
> the (single) graphics pipe, causing graphics context switches to
> occur, which are a heavyweight operation on deeply pipelined systems
> like the Onyx. Since you mentioned a pbuffer it's likely that the
> applications would be competing for framebuffer resources within the
> graphics pipe as well.
>
> This [graphics context switching] is why we discourage the use of
> gr_osview and other graphical tools while your Performer apps are
> running, by the way.
>
> Likewise, unless you have enough CPUs for _all_ the processes running
> within each application, each APP, CULL, and DRAW process is likely
> to be competing for time to be scheduled on a CPU.
>
> It's far better to incorporate it all into one application, add a few
> pfChannels containing the simple scene in a new pfPipeWindow and let
> everything run its normal course.
>
> > We have to run these apps at the same time so we tried to run the simple
> > one on an O2, that happened to be around.
> > Due to the poor graphic-hardware this app pushes an O2 over its limits,
> > and even crashes, when other processes - like new shells - are started.
> > -- Is there - apart from : don't - a general rule to run performer apps
> > on an O2 ?
>
> No special rule, Performer works fine on the O2. It's a guess but it
> sounds as if you were running out of system memory.
>
> Allan
>
> --
> Allan Schaffer allan++at++sgi.com
> Silicon Graphics http://reality.sgi.com/allan
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-- -------------------------------------------------- Dirk Baerts D.Baerts++at++Fokkerspace.nl Fokker Space BV tel (+31)71-5245296 Department AS&E fax (+31)71-5245498 P.O. Box 32070 ; 2303 DB Leiden ; The Netherlands
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