To XCB or not to XCB ...

[Daniel Stone]

On Tue, Aug 29, 2006 at 04:39:14PM +0200, Lubos Lunak wrote:
> On Sunday 27 August 2006 00:04, Jamey Sharp wrote:
> > We haven't formally released XCB yet (mostly we just need release
> > engineering at this point), and the version of Xlib built with XCB
> > should be more widely tested before declaring it stable. However, I know
> > of no correctness bugs in either.
> >
> > There is a very small, but measurable, performance hit to using XCB,
> > made marginally worse when Xlib is used on top.
> 
>  Is this about the fact that XCB is split up into a large number of 
> ridiculously small libraries that'll no doubt make ld.so choke with any 
> somewhat larger application or is this something else?

From an embedded (okay, consumer device, whatever) point of view, this
is an absolute showstopper.  We just can't afford to take that kind of
hit for every app that links libX11.

> > We know how to improve 
> > this performance somewhat, but it hasn't happened yet. Of course, when
> > apps and libraries start migrating to XCB, they'll be able to gain
> > significant performance improvements by taking advantage of XCB's better
> > API.
> 
>  Is it possible to find some more details on this? I couldn't find anything on 
> the XCB website and I wonder how XCB should provide "significant" performance 
> improvements over something that's not much more than just a tool for talking 
> the wire X protocol.

I assume Jamey's talking about how the API's asynchronous, rather than
libX11's nightmare horror show.

Cheers,
Daniel
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