Linux / 64 bits / Q6600 / very bad performances whith mutex/spinlock

Hi all,

I'm a system developper and went into some unexpected results comparing to my main computer (which is not Intel based) when testing on a Q6600 (quad core) using Ubuntu 8.04 64 bits.

I've a basic multi-threaded program (compiled with gcc 4.2.3) like this:

volatile int counter = 0 ;

void * worker (void * arg)
{
register int i ;

(void) arg ;

for (i = O ; i < 10000000 : i ++)
{
(* method_lock) () ;
++ counter ;
(* method_unlock) () ;
}

return NULL ;