Answers found to some performance/functionality problems
Answers found to some performance/functionality problems
- Subject: Answers found to some performance/functionality problems
- From: Steven Langer <email@hidden>
- Date: Thu, 17 Jul 2003 15:53:34 -0700
I believe I have explanations for some of the performance and
functionality issues I have seen with beta 3 of Apple's X11 server.
For some time I have been unable to get a program running on my Linux
system to correctly display in a window on my Mac using glx (OpenGL
over X11). I upgraded from version 4349 to version 4363 of the Nvidia
drivers today and the problem appears to have gone away.
I often use display lists on my OpenGL programs. They help cross
network OpenGL performance significantly and I had never seen them
hurt performance under Windows or Linux. On several Macs with 32 MB
of graphics memory, I found that display lists were about half as
fast as direct rendering. I borrowed a titanium laptop with 64 MB of
graphics memory. On this laptop, display lists are roughly twice as
fast as direct rendering. All of these Macs had their display set for
a million pixels or more.
I use a double-buffered, z-buffered visual that is typical of most 3D
applications that support rotation of the scene or animation. I
suspect that these buffers take up so much graphics memory that the
driver decides there isn't room for a display list in graphics
memory. The laptop with 64 MB of graphics memory has at least 32 MB
free, so I suspect that this Mac put the display list in memory and
got much higher performance.
This wouldn't be a big issue on PCs where 64 MB or more of graphics
memory has been standard for a while now. However, the graphics
memory on a Mac graphics card is frequently half the amount on the
corresponding PC card. As a result, there are a lot of G4 Macs out
there with 32 MB of graphics memory. I hope to get Mac AGP graphics
cards with 64 and 128 MB of graphics memory and see if this solves
the performance problems on the Macs that currently have 32 MB of
graphics memory.
This is encouraging news because it now looks like we can use an OS X
Mac with at least 64 MB of graphics memory to look at the large data
sets we have on our Unix servers.
Steve Langer
Lawrence Livermore National Laboratory
(NOTE: these are my own opinions, not those of LLNL)
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