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cgroup/cpu: document cpu.stat.local and clarify cpu.stat behavior

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Add documentation for the cpu.stat.local interface file, which reports
the throttled_usec stat -- the actual throttling time incurred by the
cgroup's own runqueues, which may include throttling inherited from
ancestor cgroup bandwidth limits. Unlike cpu.stat's throttled_usec
which only accounts for throttling caused by the cgroup's own CFS
bandwidth limit.

When the controller is not enabled, the stat is not reported.

Also clarify cpu.stat descriptions: note that the three base CPU usage
stats (usage_usec, user_usec, system_usec) include descendant cgroups,
and that the five CFS bandwidth stats are non-hierarchical -- they only
account for throttling caused by the cgroup's own bandwidth limit.

Signed-off-by: Sun Shaojie <sunshaojie@kylinos.cn>
Acked-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Sun Shaojie 2026-06-29 14:06:36 +08:00 committed by Tejun Heo
parent a2703c2980
commit 171569f8ee
1 changed files with 22 additions and 1 deletions
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23
Documentation/admin-guide/cgroup-v2.rst
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@ -1145,7 +1145,7 @@ will be referred to. All time durations are in microseconds.
This file exists whether the controller is enabled or not.
It always reports the following three stats, which account for all the
processes in the cgroup:
processes in the cgroup (including those in descendant cgroups):
- usage_usec
- user_usec
@ -1160,6 +1160,27 @@ will be referred to. All time durations are in microseconds.
- nr_bursts
- burst_usec
Note that the above five CFS bandwidth stats are non-hierarchical;
they only account for throttling caused by this cgroup's own bandwidth
limit, not including throttling inherited from ancestor cgroups.
cpu.stat.local
A read-only flat-keyed file.
This file exists whether the controller is enabled or not.
It reports the following stat when the controller is enabled:
- throttled_usec
Unlike the ``throttled_usec`` reported by ``cpu.stat`` which
accounts for throttling caused by this cgroup's own CFS
bandwidth limit, ``cpu.stat.local`` reports the actual
throttling time incurred by this cgroup's own runqueues,
which may include throttling inherited from ancestor
cgroup bandwidth limits.
When the controller is not enabled, this stat is not reported.
cpu.weight
A read-write single value file which exists on non-root
cgroups. The default is "100".