I am in the process of creating a C++ application that measures disk usage. I've been able to retrieve current disk usage (read and write speeds) by reading /proc/diskstats at regular intervals.
I would now like to be able to display this usage as a percentage (I find it is more user-friendly than raw numbers, which can be hard to interpret). Therefore, does anyone know of a method for retrieving maximum (or nominal) disk I/O speed programmatically on Linux (API call, reading a file, etc)?
I am aware of various answers about measuring disks speeds(eg https://askubuntu.com/questions/87035/how-to-check-hard-disk-performance), but all are through testing. I would like to avoid such methods as they take some time to run and entail heavy disk I/O while running (thus potentially degrading the performance of other running applications).
In the advent of IBM PC era, there was a great DOS utility, I forgot its name, but it was measuring the speed of the computer (maybe Speedtest? whatever). There was a bar in the 2/3 bottom of the screen, which is represented the speed of the CPU. If you had a 4.0 MHz (not GHz!) the bar occupied the 10% of the screen.
2-3 years later, '386 computers has risen, and the speed indicator bar overgrown not just the line but the screen, and it looked crappy.
So, there is no such as 100% disk speed, CPU speed etc.
The best you can do: if you program runs for a while, you can remember the highest value and set it as 100%. Probably you may save the value into a tmp file.