| Re: [PATCH v2 4/5] expose fine-grained per-cpu data for cpuacct stats [message #45929 is a reply to message #45863] |
Wed, 18 April 2012 16:14   |
Glauber Costa
Messages: 916
Registered: October 2011
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Senior Member |
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On 04/18/2012 09:30 AM, Sha Zhengju wrote:
> On Mon, Apr 9, 2012 at 6:25 PM, Glauber Costa<glommer@parallels.com> wrote:
>> > The cpuacct cgroup already exposes user and system numbers in a per-cgroup
>> > fashion. But they are a summation along the whole group, not a per-cpu figure.
>> > Also, they are coarse-grained version of the stats usually shown at places
>> > like /proc/stat.
>> >
>> > I want to have enough cgroup data to emulate the /proc/stat interface. To
>> > achieve that, I am creating a new file "stat_percpu" that displays the
>> > fine-grained per-cpu data. The original data is left alone.
>> >
>> > The format of this file resembles the one found in the usual cgroup's stat
>> > files. But of course, the fields will be repeated, one per cpu, and prefixed
>> > with the cpu number.
>> >
>> > Therefore, we'll have something like:
>> >
>> > cpu0.user X
>> > cpu0.system Y
>> > ...
>> > cpu1.user X1
>> > cpu1.system Y1
>> > ...
>> >
> Why not show the all-cpu data together with the per-cpu one? I think
> the total one
> is an usual concern in most cases.
>
Because that is a trivial operation that can be done in userspace.
In general, I see no value in formatting this file any further if we'll
have to get to userspace for the final solution anyway.
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