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SubjectRe: [PATCH v4 23/25] memcg: propagate kmem limiting information to children
On 06/18/2012 04:37 PM, Kamezawa Hiroyuki wrote:
> (2012/06/18 19:28), Glauber Costa wrote:
>> The current memcg slab cache management fails to present satisfatory hierarchical
>> behavior in the following scenario:
>>
>> -> /cgroups/memory/A/B/C
>>
>> * kmem limit set at A
>> * A and B empty taskwise
>> * bash in C does find /
>>
>> Because kmem_accounted is a boolean that was not set for C, no accounting
>> would be done. This is, however, not what we expect.
>>
>
> Hmm....do we need this new routines even while we have mem_cgroup_iter() ?
>
> Doesn't this work ?
>
> struct mem_cgroup {
> .....
> bool kmem_accounted_this;
> atomic_t kmem_accounted;
> ....
> }
>
> at set limit
>
> ....set_limit(memcg) {
>
> if (newly accounted) {
> mem_cgroup_iter() {
> atomic_inc(&iter->kmem_accounted)
> }
> } else {
> mem_cgroup_iter() {
> atomic_dec(&iter->kmem_accounted);
> }
> }
>
>
> hm ? Then, you can see kmem is accounted or not by atomic_read(&memcg->kmem_accounted);
>

Accounted by itself / parent is still useful, and I see no reason to use
an atomic + bool if we can use a pair of bits.

As for the routine, I guess mem_cgroup_iter will work... It does a lot
more than I need, but for the sake of using what's already in there, I
can switch to it with no problems.





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