[Xcb] Re: To XCB or not to XCB ...

Lubos Lunak l.lunak at suse.cz
Tue Aug 29 07:39:14 PDT 2006

On Sunday 27 August 2006 00:04, Jamey Sharp wrote:
> On Sat, Aug 26, 2006 at 10:07:26AM -0700, Kean Johnston wrote:
> > One other question. For creating a new distribution what is the
> > conventional wisdom about XCB? If I dont include it, will it
> > cripple X in any way? If I do, will there be any performance
> > benefits or deficits? The web page wasn't very enlightening,
> > so if someone can put forth an educated opinion, I would
> > greatly appreciate it. Thanks.
> 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?

> 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've been running essentially the current version of Xlib/XCB on my
> laptop in lieu of stock Xlib since early this year, up to fixing a
> couple of bugs in that time, and I don't believe there is any
> perceptible performance difference on real applications,

 Too bad believing happens to be probably the worst tool for measuring 

> nor have I 
> encountered any bugs in months. I've been testing out a bunch of new X
> apps recently, too. :-)

Lubos Lunak
KDE developer
SUSE LINUX, s.r.o.   e-mail: l.lunak at suse.cz , l.lunak at kde.org
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