cpu limits status report

[rudo tomori]

Hi,
the goal of my gsoc project is to enable the system administrators to
configure %CPU limits using the rctl command. So that they can for
example limit a particular user to 50% cpu time.

Last week I added a new resource to the racct/rctl infrastructure that
stores the %CPU utilization. I can now start a cpu intensive process
that would normally consume almost 100% cpu time and using rctl, I can
limit it to 40% for example. This works and I can watch it in top how
the %cpu utilization for the process goes down to about the specified
limit.

There are still problems that I will try to address this week:

1. I may sometimes skip setting the pcpu resource for some processes.
This makes now the aggregate pcpu utilization (for example per-user
cpu utilization) incorrect.

2. I probably need to change the formula that calculates the CPU
percentage utilization, because it does not work well for short-lived
processes. I think I will use the same formula as is used in the ps
command.

rudo