On Tue, Apr 05, 2022 at 08:26:59AM +0200, Michal Hocko wrote:
>On Tue 05-04-22 02:22:18, Wei Yang wrote:
>> On Mon, Apr 04, 2022 at 11:27:53AM +0200, Michal Hocko wrote:
>> >On Sun 03-04-22 02:08:33, Wei Yang wrote:
>> >> After commit bef8620cd8e0 ("mm: memcg: deprecate the non-hierarchical
>> >> mode"), we won't have a NULL parent except root_mem_cgroup. And this
>> >> case is handled when (memcg == root).
>> >>
>> >> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>> >> CC: Roman Gushchin <roman.gushchin@xxxxxxxxx>
>> >> CC: Johannes Weiner <hannes@xxxxxxxxxxx>
>> >
>> >Acked-by: Michal Hocko <mhocko@xxxxxxxx>
>> >Thanks!
>> >
>>
>> Thanks for the ack. When reading the code, I found one redundant check in
>> shrink_node_memcgs().
>>
>> shrink_node_memcgs
>> mem_cgroup_below_min
>> mem_cgroup_supports_protection
>> mem_cgroup_below_low
>> mem_cgroup_supports_protection
>>
>> I am not sure it worthwhile to take it out.
>>
>> shrink_node_memcgs
>> mem_cgroup_supports_protection
>> mem_cgroup_below_min
>> mem_cgroup_below_low
>>
>> Look forward your opinion.
>
>I guess you refer to mem_cgroup_is_root check in mem_cgroup_supports_protection,
>right?
>
>You are right that the check is not really required because e{min,low}
>should always stay at 0 for the root memcg AFAICS. On the other hand the
>check is not in any hot path and it really adds clarity here because
>protection is not really supported on the root memcg. So I am not this
>is an overall win.
Agree.
>--
>Michal Hocko
>SUSE Labs
--
Wei Yang
Help you, Help me
