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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