On Sat, 2007-12-15 at 11:07 -0700, Brian Paul wrote:
> Keith Packard wrote:
> > The pthreads library introduces significant overhead for single-threaded
> > applications,
> 
> Just out of curiosity, have you made some measurements?

Yeah, we're seeing 5-10% locking overhead in some preliminary i965 code
which is hitting mutexes fairly hard. A lot of that is caused by
reference counting, which could switch to atomic instructions, but
still, it might be nice to simply skip mutexes for single threaded apps.

> Sounds like a good idea.  Any GL app that's multithreaded should be 
> linking with -lpthreads in the first place so I don't see much risk for 
> breakage (undefined thread funcs at run/load time).

I'm cooresponding with Ulrich to see if he's got a better plan. Right
now, the only way I've gotten it working is by using a separate library
with glthreads.c. Ick.

> I guess the new code would go in the glthreads.c file, protected by 
> #ifdef __GNU_C__ (or whatever).

Nope, it's in a separate file and built into a separate library. I don't
like this, but I haven't figured out how to make it work inside libGL.

> I say go ahead, but maybe not on mesa_7_0_branch for now.

Yeah, I'd stick it on a branch. The only change it makes right now is to
build this new library and have libGL link to that instead of -lpthread,
so it's nicely isolated.

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