[Xcb] Question about xcb performance and threading support

Julien Danjou julien at danjou.info
Tue Feb 17 05:24:07 PST 2009

Hi Benoît,

At 1234876657 time_t, Benoît Minisini wrote:
> I have currently using valgrind / callgrind & kcachegrind with the Gambas IDE 
> to try to understand why QT4.4 is slower than QT3.
> I noticed in the Gambas/QT4 kcachegrind output that pthread_mutex_lock and 
> pthread_mutex_unlock take respectively 1.41% and 1.52% of the execution time.
> The Gambas/QT3 kcachegrind output gives approximatively the same result.
> I am a bit disappointed with that: using 3% of the total execution time just 
> to manage threads in a library for a completely non-threaded application.
> Is there a way to optimize that? For example having a single-threaded version 
> of libxcb. Or is there something more complex behind that? (I guess so...)
> My system is a Mandriva 2009 with libxcb 1.1.91.

I might be wrong, but this can be related to the small size of the XCB buffer.
I suggest you retry with libxcb >= 1.1.92 which has a bigger buffer by default
(16k rather than 4k before).

Julien Danjou
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