Hello everyone,
I have an `Embedded Linux(Kernel 2.6.37)` running on `ARM`. There's a
default `top` from `busybox 1.13.2`. And I build a `procps-ng 3.3.11` via
cross compile to run on this `Linux`. I found that the process's `%cpu` via
`top` output from `busybox` and `procps-ng` are different.
For example, the `%cpu` of one process, `procps-ng top` display about 30%,
but `busybox top` display only about 10%. The total `%cpu` from `procps-ng
top` and `busybox top` are the same.
Then I read the calculation source code of `busybox` and `procps-ng`. I
found that they really have different calculation formula for one process's
`%cpu`.
<pre><code>
- busybox top:
CPU% = s->pcpu/sum(s->pcpu) * busy_cpu_ticks/total_cpu_ticks
(pcpu is delta of sys+user time between samples)
- procps-ng top:
CPU% = s->pcpu/total_cpu_ticks
</code></pre>
Why the two projects choose different calculation formula? Do they designed
for different application case?
Looking forward to your reply.
Thanks very much!
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