rb_thread_sleep   320 include/ruby/intern.h void rb_thread_sleep(int);
rb_thread_sleep  4644 io.c           	    rb_thread_sleep(1);
rb_thread_sleep  2285 process.c      		rb_thread_sleep(1);
rb_thread_sleep  2289 process.c      		rb_protect((VALUE (*)())rb_thread_sleep, 1, &state);