On Tue, 14 Oct 2003, Alexander Shopov wrote:

>> Kernel modules are not inherently faster.  the reason directx (and
>> openGL) seem so fast on windows is because the manufacturers and MS
>> tweak the drivers for every last bit of performance.  Plus they are
>> able to utilize interfaces that are not accessable in xfree86 due to IP
>> concerns.  Some xfree86 drivers actually are faster or support more
>> features than their windows counterparts.
>> 
>Hi Alex,
>How can we prove this with real life data?
>I do realize XFree86 is VERY fast in some situations - for example I 
>have seen Quake 3 running faster on GNU/Linux than on Windows - on the 
>same hardware.

I'm not quite convinced that that is an objective comparison 
however.  Was Quake 3 running in both operating systems with the 
exact same 3D settings?  Windows drivers support the full 
hardware featureset, and games are more likely IMHO to use the 
full hardware set of features in Windows.  The XFree86 open 
source drivers support only a limited set of the functionality 
available in Windows.  If you disable all hardware features in 
Windows which are not available under Linux, and configure 
everything else to be as close as possible for an accurate apples 
to apples comparison does Linux perform better?

My experience is that while Linux DRI support is decent for most 
users, it doesn't outperform Windows.  One needs to also make 
sure the same AGP mode is being used, etc. and that MTRR is 
functional...

Of course I'm not discounting your claims, just a bit skeptical 
as to how the exact tests were ran, and how it was instrumented, 
or if it was just a placebo'ish "it seems faster" type of thing, 
etc...


>What can we really do to prove to infidels that XFree86 works great? 
>Logic most of the times fails, explanation like usage of IPC, latency 
>tests etc. also fails, people just scream "Kernel graphics g0000d, X 
>b4444d" and it is demos like this that help me shut them up.
>What can we do?

Quite frankly...  random uninformed people making claims that X 
is slow, without any shred of a clue or properly deduced 
scientifically measured and reproduceable instrumented data, will 
always be out there.  We can't stop people from spreading 
unfounded rumours nor from making random guesses as to why they 
or someone they know may be experiencing slowdowns in some 
application or another.  X itself isn't slow by any stretch of 
the imagination, and there have been studies done that show this 
precicely.  I don't think trying to "prove" anything to people 
who will believe whatever they want to believe helps us any at 
all personally...

The best thing any of us can do, is continue to properly and 
scientifically analyze the X server, it's video drivers, and 
other related technologies, profile them, optimize them, etc.

Right now, the biggest hit on the desktop is probably 
unaccelerated RENDER operations.  That's what most users likely 
see as "desktop slowdowns" currently.  Over time, those things 
will improve as people write support.

The most important thing, when comparing Linux/X/XFree86 to 
Windows performancewise however, is that apples to apples 
comparisons are being made, and to understand exactly what 
component and/or level of the puzzle any problems that are found 
reside in.  In the case of RENDER for example, that isn't an X11 
performance problem, it is an XFree86 video driver limitation 
currently.  Nothing that can't be overcome in the future.

For video games and 3D however (to get back on specific topic), 
proprietary drivers that implement all of the hardware's special 
do-dads are very likely to always outperform the OSS drivers, 
simply because more resources are spent on the proprietary 
drivers, and more engineers with more deeper knowledge of the 
hardware are working on them.

Take care,
TTYL


-- 
Mike A. Harris

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