On 2022/8/12 18:14, Michal Koutný wrote:
> Hello Chengming.
>
> On Mon, Aug 08, 2022 at 07:03:40PM +0800, Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> wrote:
>> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
>> index dd84e34bc051..ade40506ab80 100644
>> --- a/Documentation/admin-guide/cgroup-v2.rst
>> +++ b/Documentation/admin-guide/cgroup-v2.rst
>> @@ -968,6 +968,13 @@ All cgroup core files are prefixed with "cgroup."
>> killing cgroups is a process directed operation, i.e. it affects
>> the whole thread-group.
>>
>> + cgroup.psi
>> + A read-write single value file that allowed values are "0" and "1".
>> + The default is "1".
>> +
>> + Writing "0" to the file will disable the cgroup PSI stats accounting.
>> + Writing "1" to the file will re-enable the cgroup PSI stats accounting.
>> +
>
> I'd suggest explaining here explicitely, this control attribute is not
> hierarchical (i.e. PSI accounting in a cgroup does not affect accounting
> in descendants and doesn't need pass enablement via ancestors from
> root). And the purpose that it "saves" cycles (where).
Thanks for the suggestion and explanation!
Could you help take a look if there is anything to improve?
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -968,6 +968,23 @@ All cgroup core files are prefixed with "cgroup."
killing cgroups is a process directed operation, i.e. it affects
the whole thread-group.
+ cgroup.pressure
+ A read-write single value file that allowed values are "0" and "1".
+ The default is "1".
+
+ Writing "0" to the file will disable the cgroup PSI accounting.
+ Writing "1" to the file will re-enable the cgroup PSI accounting.
+
+ This control attribute is not hierarchical, so disable or enable PSI
+ accounting in a cgroup does not affect PSI accounting in descendants
+ and doesn't need pass enablement via ancestors from root.
+
+ The reason this control attribute exists is that PSI accounts stalls for
+ each cgroup separately and aggregates it at each level of the hierarchy.
+ This may cause non-negligible overhead for some workloads when under
+ deep level of the hierarchy, in which case this control attribute can
+ be used to disable PSI accounting in the cgroups.
+
