Ubuntu 18.04 LTS Performance Tuning or not

After several experiments, I confirmed that previous performance tuning for Ubuntu 16.04 LTS does not fit for Ubuntu 18.04 LTS. The previous performance tuning, such as hard drive read/write, will slow down the performance of Ubuntu 18.04 LTS. If you implemented such tuning in Ubuntu 18.04 LTS and noticed the performance drops, you may consider to turn it off or disable it.

For example,

echo 1024 | sudo tee /sys/block/sda/queue/read_ahead_kb
echo 1024 | sudo tee /sys/block/sda/queue/nr_requests

That's all! See you.