Gareth Hughes wrote:
It is critically important for OpenGL drivers to have fast (single-instruction) access to thread local variables. ... While glibc's new thread library implementation has many benefits, particularly to application programmers (with support for the new keyword '__thread', and so on), it basically forces a function call per thread local variable access for situations like the one I described above. ... Comments, questions are welcome.
Hi Gareth, I forwarded your note to the NPTL mailing list. Roland McGrath replied, and suggests that you might want to reread the TLS paper (I think he's referring to http://people.redhat.com/drepper/nptl-design.pdf, which appears to be offline at the moment); also look at the GCC implementation of __thread, and note -ftls-model and __attribute__ ((tls_model)).
If that didn't make any sense, it's probably because I mangled Roland's words; you might want to ask him what he meant. - Dan