Why does the computer slow down with almost free CPU and RAM?

Question

linux

Sometimes computers start to "blunt". Usually not immediately after installing the OS, but after many months or years. There is a lethargy when opening windows, a slow response to keystrokes and mouse clicks. Programs visually hardly toss and turn. Although the CPU and RAM are quite free. Sometimes it is observed permanently, sometimes from time to time.
I usually came across this on Windows, and I thought that this was just a feature of Windows, and it just needs to be rearranged regularly. But now I saw almost the same thing on Ubuntu.
Who can be to blame for this delay? Where to dig?

Answer 1

Bad sectors on the screw (see dmesg, smartctl). Temperature of the processor / video card (sensors). Curved driver/crooked iron (see vmstat, cat /proc/interrupts).

Answer 2

Ubuntu is to blame. Both Win and Ubuntu are equally crooked. Reinstall the OS, if everything passes - it's in the software.

Answer 3

I would start with hdd diagnostics like iostat.
The bottleneck in the computer is still the hard drive.