Re: [PATCH v3 5/6] Also record sleep start for a task group

On Wed, 2012-05-30 at 16:24 +0400, Glauber Costa wrote:

sleep_start is not for iowait. This is for idle. And I know no other way 
to collect idle time per cgroup, other than the time during which it was 
out of the runqueue.

Now what you say about the sleepers don't make that much sense for idle 
because this information is per-cpu as well.

When the se is being dequeued, it means none of its children is running 
on that runqueue. That's idle. 

But does that mean the cgroup is idle? Its impossible to re-construct
the machine state from this per-cpu data if your definition of
cgroup-idle is the time when _all_ cpus are idle.