Juan Saenz-Diez (jrsdm++at++hotmail.com)
Thu, 01 Jul 1999 21:08:38 PDT
For an almost unspoiled frame rate evaluation, I would suggest that you turn
off stats and type in some terminal window something like:
sar -g 1 1000
and watch the last column for actual swapbuffer rate.
Regards,
Yuri.
>From: Geoff Levner <g.levner++at++acsys.it>
>To: info-performer++at++sgi.com
>Subject: the elusive constant frame rate
>Date: Thu, 01 Jul 1999 13:24:40 +0200
>
>I have a MultiGen scene which runs in perfly at 30-60 Hz in
>PFPHASE_FREE_RUN, and I would like for it to run at a constant 30 Hz.
>Sounds easy. But if I set the phase to PFPHASE_LOCK (or FLOAT, or
>LIMIT) and set the target frame rate to 30, the actual frame rate varies
>between 20 and 30 Hz, or sometimes even 15. And if I set the target
>frame rate to 15, the actual frame rate can go as low as 7.5!
>
>Can anyone tell me what is happening here?
>
>On further investigation, I noticed that the actual frame rate is
>slowest when the viewing frustum is the most uncluttered. That is, with
>a target of 15 Hz, I get 15 Hz somewhere in the middle of the scene, but
>7.5 Hz when looking up toward the sky (which is the default pfEarthSky,
>no textures). In fact, anything I do to increase drawing time (such as
>turning off culling) actually increases the frame rate (sic!). If you
>look at the stats when the frame rate is lagging, everyone is waiting on
>the draw process, which consists of a tiny solid line followed by a
>looooong dotted line.
>
>Even without my scene, I found a similar phenomenon in perfly. If I run
>perfly with an empty scene and lock the frame rate to 15 Hz --
>
> perfly -P 1 -r 15 -E skyclear
>
>-- and then turn on the statistics, the actual frame rate is 7.5....
>
>All tests were done on an Onyx2 IR2 with 4 CPUs running IRIX64 6.5 and
>Performer v2.2.2.
>
>HELP!
>
>--
>Geoff Levner -- g.levner++at++acsys.it
>ACS Studio, via Aurelia 58, 00165 Roma, Italy
>tel. +39-063936331, fax +39-0639363317
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