What does pg_top show?

Question

linux

Most likely the question is simple, but I think you will help faster than I will look for myself, thanks in advance.
pg_top shows the following values:
0 buffer r/s,
100 hit%,
Can you tell me what these values ​​are and how they change? The fact that r / s is reading per second, w / s is writing (probably), but what are they measured in? What is hit?
I also see I/O (DB I/O: 0 reads/s, 0 KB/s ) - what is reads/s measured in?

Answer 1

buffer how many are in the buffer for reading (requests per second)
hit - how many requests subtracted from the cache (% ratio)
I / O - these are input / output (read / write) operations per second (or in kilobytes) to disk.