xubuntu:yagihiro% time ./use_mmap
./use_mmap 0.02s user 0.02s system 7% cpu 0.622 total
xubuntu:yagihiro% time ./use_mmap
./use_mmap 0.03s user 0.02s system 7% cpu 0.637 total
xubuntu:yagihiro% time ./use_mmap
./use_mmap 0.03s user 0.02s system 8% cpu 0.640 total
xubuntu:yagihiro% time ./use_mmap
./use_mmap 0.04s user 0.01s system 7% cpu 0.631 total
xubuntu:yagihiro% time ./use_read
./use_read 0.00s user 0.24s system 7% cpu 3.089 total
xubuntu:yagihiro% time ./use_read
./use_read 0.03s user 0.02s system 7% cpu 0.741 total
xubuntu:yagihiro% time ./use_read
./use_read 0.03s user 0.03s system 7% cpu 0.740 total
xubuntu:yagihiro% time ./use_read
./use_read 0.04s user 0.02s system 8% cpu 0.728 total
xubuntu:yagihiro% time ./use_read
./use_read 0.02s user 0.03s system 7% cpu 0.747 total