| How to draw values for /proc/stat [message #44383] |
Mon, 05 December 2011 09:32  |
Glauber Costa
Messages: 916
Registered: October 2011
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Senior Member |
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Hi,
Specially Peter and Paul, but all the others:
As you can see in https://lkml.org/lkml/2011/12/4/178, and in my answer
to that, there is a question - one I've asked before but without that
much of an audience - of whether /proc files read from process living on
cgroups should display global or per-cgroup resources.
In the past, I was arguing for a knob to control that, but I recently
started to believe that a knob here will only overcomplicate matters:
if you live in a cgroup, you should display only the resources you can
possibly use. Global is for whoever is in the main cgroup.
Now, it comes two questions:
1) Do you agree with that, for files like /proc/stat ? I think the most
important part is to be consistent inside the system, regardless of what
is done
2) Will cpuacct stay? I think if it does, that becomes almost mandatory
(at least the bind mount idea is pretty much over here), because drawing
value for /proc/stat becomes quite complex.
The cpuacct cgroup can provide user, sys, etc values. But we also have:
* nr_context_switches,
* jiffies since boot,
* total_forks,
* nr_running,
* nr_iowait,
Now I doubt any of us want to see /proc/stat extended to accommodate
things like nr_context_switches, or even worse, nr_running. The way I
see it, there are two options here:
a) moving everything to cpu cgroup so we keep all values being drawn
from the same place
b) Collect that info from multiple places in a transparent way. ctx,
nr_running and nr_iowait will probably come from cpu. jiffies can
come from wherever, and maybe we can even draw total_forks
from Frederic's and avoid counting it twice.
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