[Mesa-dev] Performance glxSwapBuffers 32 bit vs. 64 bit

Michel Dänzer michel at daenzer.net
Thu Nov 10 09:42:13 PST 2011

On Don, 2011-11-10 at 11:01 +0100, Theiss, Ingo wrote: 
> The function calls of mesa/state_tracker/st_cb_readpixels.c:382 ->
> st_readpixels and mesa/main/pack.c:552 -> _mesa_pack_rgba_span_float
> clearly stands out when comparing the 32 bit and 64 bit profile.

I'm afraid that's a red herring, as I don't think glXSwapBuffers calls
glReadPixels under any circumstances. I suspect the time inside
glXSwapBuffers isn't spent on CPU cycles but rather waiting for some
kind of event(s). Offhand I don't know any better way to debug that than
attaching gdb, interrupting execution every now and then and hoping to
catch it somewhere inside glXSwapBuffers. Maybe others have better

Earthling Michel Dänzer           |                   http://www.amd.com
Libre software enthusiast         |          Debian, X and DRI developer

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