Re: [PATCH] memcg: make it work on sparse non-0-node systems

Jiri Slaby
2019-04-29T11:55:32Z

On 29. 04. 19, 13:30, Michal Hocko wrote:
> On Mon 29-04-19 12:59:39, Jiri Slaby wrote:
> [...]
>> static inline bool list_lru_memcg_aware(struct list_lru *lru)
>> {
>> - /*
>> - * This needs node 0 to be always present, even
>> - * in the systems supporting sparse numa ids.
>> - */
>> - return !!lru->node[0].memcg_lrus;
>> + return !!lru->node[first_online_node].memcg_lrus;
>> }
>>
>> static inline struct list_lru_one *
>
> How come this doesn't blow up later - e.g. in memcg_destroy_list_lru
> path which does iterate over all existing nodes thus including the
> node 0.

If the node is not disabled (i.e. is N_POSSIBLE), lru->node is allocated
for that node too. It will also have memcg_lrus properly set.

If it is disabled, it will never be iterated.

Well, I could have used first_node. But I am not sure, if the first
POSSIBLE node is also ONLINE during boot?

thanks,
--
js
suse labs