Re: [PATCH cgroup/for-5.8] cgroup: add cpu.stat file to root cgroup

From: Johannes Weiner
Date: Wed May 27 2020 - 12:08:53 EST

On Tue, May 26, 2020 at 01:08:00PM -0700, Boris Burkov wrote:
> Currently, the root cgroup does not have a cpu.stat file. Add one which
> is consistent with /proc/stat to capture global cpu statistics that
> might not fall under cgroup accounting.
> We haven't done this in the past because the data are already presented
> in /proc/stat and we didn't want to add overhead from collecting root
> cgroup stats when cgroups are configured, but no cgroups have been
> created.
> By keeping the data consistent with /proc/stat, I think we avoid the
> first problem, while improving the usability of cgroups stats.
> We avoid the second problem by computing the contents of cpu.stat from
> existing data collected for /proc/stat anyway.
> Signed-off-by: Boris Burkov <boris@xxxxxx>
> Suggested-by: Tejun Heo <tj@xxxxxxxxxx>

Looks good to me, but Boris can you please update
Documentation/admin-guide/cgroup-v2.rst as well in this patch?

A read-only flat-keyed file which exists on non-root cgroups.