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

[Glauber Costa]

On 05/30/2012 04:44 PM, Peter Zijlstra wrote:
> 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.
It is idle for that runqueue, aka cpu. The cgroup itself is idle when 
all cpus are idle. And yes, then you have 2s per sec of idle in a 2-way 
system.

That's pretty much how a physical box works as well.

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