In the machine are you using an SSD ?
This link discusses how SSD are different speeds if booted from battery or AC power, and the percentage difference varies by the manufacturer of the SSD, there can be some work arounds possibly if it is after suspend or speed decreasing by #'s of read/writes re; (Trim ?) - https://askubuntu.com/questions/844459/u...emely-slow
This link discusses how SSD are different speeds if booted from battery or AC power, and the percentage difference varies by the manufacturer of the SSD, there can be some work arounds possibly if it is after suspend or speed decreasing by #'s of read/writes re; (Trim ?) - https://askubuntu.com/questions/844459/u...emely-slow