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Re: What is the reason for tls_model("initial-exec") in Mesa?



On Sat, 11 Dec 2010 18:22:32 +0100, "Raphael Wimmer" <raphael.wimmer@ifi.lmu.de> wrote:
> Hi,
> 
> it seems that only compiling Mesa without "--enable-glx-tls" fixes the  
> problem.
> I have run a Nexuiz demo game as a benchmark for Mesa with/without TLS,  
> and the results seem very similar:
> 
> Mesa compiled with TLS initial-exec:
> 1184 frames 62.7560000 seconds 18.8667219 fps, one-second fps min/avg/max:  
> 10 19 60 (64 seconds)
> 
> Mesa compiled without GLX TLS:
> 1184 frames 62.6740000 seconds 18.8914063 fps, one-second fps min/avg/max:  
> 10 19 60 (64 seconds)
> 
> Mesa compiled with TLS global-dynamic:
> 1184 frames 63.1370000 seconds 18.7528707 fps, one-second fps min/avg/max:  
> 10 19 60 (64 seconds)

nexuiz is very much GPU-bound for me at that framerate (~30% cpu usage),
so I'm guessing you didn't actually test the effect of disabling TLS at
all.  You'd need something CPU bound to really show the difference of a
CPU-side optimization like this.  I've found cairo-perf-trace with
cairo-gl on my hardware to be one of the most CPU-bound apps I can come
up with (but even then, we've got the CPU usage down to the point where
it's at the edge of being GPU-bound).  Some old GL screensavers that
never got updated for modern GL API, like hyperspace, might also work.

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