[Xcb] XPutImage and context switches / roundtrips?

Clemens Eisserer linuxhippy at gmail.com
Wed Sep 10 13:12:58 PDT 2008

Hi Peter,

Thanks a lot for your reply.

> No. XCB automatically flushes its internal buffers whenever it runs out
> of space.
>> I guess on single-core systems this means two context switches per flush?
> You're thinking of sync, not flush.

Well, but when xcb does an automatic flush because the buffer is full
doesn't that mean it would like to have its buffer emptied?
Having the buffer freed means it has to be moved somewhere - in this
case to the x-server, or am I wrong?
Either the image-data is buffered somewhere with a >4kb buffer (maybe
in the kernel or somewhere else), or the kernel has to context-switch
to the x-server to process the flushed data.

Thanks in advance, Clemens

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