[Xorg] Chromium vs GLX protocol

[Brian Paul]

Jon Smirl wrote:
> Slashdot is saying that SGI is going to port their clustered ATI
> graphics to Linux in the near future. The SGI page says this code is
> based on Chromium. I've read that the network protocol of Chromium is
> far better than the GLX protocol, especially in the area of state
> management. Does anyone have experience with both protocols and can
> comment on how they compare?

Sure...

> If the Chromium protocol really is a lot better would it make sense to
> evaluate shifting our focus from GLX to the Chromium protocol? In the
> long  run the coming shift to things like X on GL and Glitz may
> ultimately move a lot of network traffic from the X protocol to one of
> the GL ones. If Chromium is significantly better wouldn't it be wiser
> to change the X server GL protocol now rather than later?

The Chromium command packer packs GL commands more densely than GLX. 
A one-byte opcode is used for most commands and operands are packed 
tightly in memory.  Opcodes are packed separate from the operands in a 
unique way too.

Chromium also has a state tracking system which can eliminate 
redundant commands from being packed/sent.  It's pretty complicated 
though and still a source of bugs.

I wouldn't say that Chromium's packer is a *lot* better than GLX.  And 
I wouldn't advocate switching to it.  GLX interoperability is 
important and making such a switch would upset that.  I don't think 
the effort to switch would be worth the trouble.  Performance-wise, I 
think the gains would be quite modest.

-Brian