Re: Comparing X performance on Debian and Solaris
On Fri, Jul 26, 2002 at 08:35:11PM -0700, Sageev George wrote:
> I've been noticing that my Solaris installation
> on my Ultra 30 (with Creator 3D) seems more
> "accelerated" than the Debian installation
> when comparing a couple things in X.
Which version of the Creator 3D card? They don't all have
the same performance characteristics.
> For instance, Netscape is very jumpy
> during scrolling in Debian, but smooth
> in Solaris, and if I drag windows around
> the workspace, in Debian the windows lag
> behind significantly, while in Solaris the
> lag is a lot smaller (but still there).
It might be more useful for you to run x11perf on both systems and see
which particular primitives are unexpectedly fast or slow. From this
description it sounds like the Linux drivers may not be using vertical
scrolling (which has hardware acceleration), and may not be using the
fastest mode for bitmap copies (which do not have hardware acceleration).
General blits were left out of the Creator design because the UPA bus
is fast enough that it doesn't matter much; but it is slow enough to
be noticable. But if the window drags are being done as a bunch of
single reads from the framebuffer, that could be significantly improved
on. Under Solaris, this is done by using the hand-coded gcopy, which
does block reads and maintains temporary workspace in registers. (It's
also profitable to do a block (8x size) read of a region instead of 2
or 3 individual reads, in case anyone is tuning at that level.)
> I have read that there is proprietary microcode
> that enables the accelerated functions on
> an Elite 3D. Is there something similar
> missing from the XFree86 4.0 driver for
> the Creator 3D? I had tried recompiling
> the kernel in Debian, but I didn't create any
> kernels that were able to speed the graphics
> to the level that they are on the Solaris
> installation.
There isn't any downloadable microcode in the Creator card. What
microcode there is exists in a mask ROM.
> Does anyone have any thoughts on what
> I might be doing wrong in my Debian installation?
> Or, is this the behavior to expect from
> Debian Woody 2.4 kernels?
This is unlikely to be attributable to the kernel: The register layout
on the Creator ASIC was specifically designed to allow some pages to be
mapped directly by user processes, and commands to be sent to the card
without the overhead of a system call. It's far more likely that the X
server under Linux doesn't have all of the possible optimizations.
Jon Leonard
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