[Devel] Re: [PATCH v2 4/5] expose fine-grained per-cpu data for cpuacct stats

[Glauber Costa]

On 04/18/2012 09:30 AM, Sha Zhengju wrote:
> On Mon, Apr 9, 2012 at 6:25 PM, Glauber Costa<glommer at 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.