eventfd is passing counting value.
eventfd_write(fd, 1);
-> read result: 1
eventfd_write(fd, 1);
eventfd_write(fd, 1);
-> read result: 2
eventfd is passing counting value.
eventfd_write(fd, 1);
-> read result: 1
eventfd_write(fd, 1);
eventfd_write(fd, 1);
-> read result: 2