On Wed, Jan 16, 2013 at 6:21 PM, Saul Tamari <stamari@xxxxxxxxx> wrote: > I checked the shared library and parts of it are not compiled with -fpic. > So that could be the cause of the problematic TLS behavior I'm seeing? > The run-time linker doesn't prepare the loaded TLS variables > correctly? If you put code that accesses TLS variables into a shared library, and that code was not compiled with -fpic/-fPIC nor with -ftls-model=global-dynamic, then accessing the TLS variables will read the wrong values. > Can -fpic compilation cause significant performance or memory > footprint changes on modern x86 Xeon processors? Yes, it's about a 3 or 4% performance hit. Putting code not compiled with -fPIC in a shared library will slow down program startup, and make the program less secure because the text segment will be writable. Also, the shared library will not actually be shared: each process will have its own copy in virtual memory. Whether these things matter to you depends on how you run your code. Ian
