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SubjectRe: [PATCH] Add hierarchical accounting to cpu accounting controller
On Wed, 05 Nov 2008 11:31:32 +0800
Li Zefan <lizf@cn.fujitsu.com> wrote:

> >> cpuacct was designed to count cpu usage of a group of tasks, and now some people
> >> want it to also take child group's usage into account, so I think this is a feature
> >> request but not a bug fix.
> >>
> >
> > I disagree. The child is a part of the parent's hierarchy, and therefore
> > its usage should reflect in the parent's usage.
> >
>
> In memcg the child's usage doesn't reflect in its parent's usage. ;)
>
> Balbir just posted a patchset to add hierarchy support in memcg, and added memory.feature
> to disable/enable this feature. Is it for performance only or also for keeping the user
> interface/behavior unchanged?

The main reason is performance.

And one of memcg's purpose is isolating resource usage of groups. Sum of usage
is not very important sometimes. (we have /proc/meminfo ;)
Sum of usage can be easily calculcated by user land and we don't have to pay
the cost for it in the kernel.

Thanks,
-Kame



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