KAMEZAWA Hiroyuki wrote:
> On Fri, 07 Mar 2008 18:32:20 +0300
> Pavel Emelyanov <[EMAIL PROTECTED]> wrote:
>
>> This allows us two things basically:
>>
>> 1. If the subgroup has the limit higher than its parent has
>> then the one will get more memory than allowed.
>> 2. When we will need to account for a resource in more than
>> one place, we'll be able to use this technics.
>>
>> Look, consider we have a memory limit and swap limit. The
>> memory limit is the limit for the sum of RSS, page cache
>> and swap usage. To account for this gracefuly, we'll set
>> two counters:
>>
>> res_counter mem_counter;
>> res_counter swap_counter;
>>
>> attach mm to the swap one
>>
>> mm->mem_cnt = &swap_counter;
>>
>> and make the swap_counter be mem's child. That's it. If we
>> want hierarchical support, then the tree will look like this:
>>
>> mem_counter_top
>> swap_counter_top <- mm_struct living at top
>> mem_counter_sub
>> swap_counter_sub <- mm_struct living at sub
>>
> Hmm? seems strange.
>
> IMO, a parent's usage is just sum of all childs'.
> And, historically, memory overcommit is done agaist "memory usage + swap".
>
> How about this ?
> <mem_counter_top, swap_counter_top>
> <mem_counter_sub, swap_counter_sub>
> <mem_counter_sub, swap_counter_sub>
> <mem_counter_sub, swap_counter_sub>
>
> mem_counter_top.usage == sum of all mem_coutner_sub.usage
> swap_counter_sub.usage = sum of all swap_counter_sub.usage
I've misprinted in y tree, sorry.
The correct hierarchy as I see it is
<mem_couter_0>
+ -- <swap_counter_0>
+ -- <mem_counter_1>
| + -- <swap_counter_1>
| + -- <mem_counter_11>
| | + -- <swap_counter_11>
| + -- <mem_counter_12>
| + -- <swap_counter_12>
+ -- <mem_counter_2>
| + -- <swap_counter_2>
| + -- <mem_counter_21>
| | + -- <swap_counter_21>
| + -- <mem_counter_22>
| + -- <swap_counter_22>
+ -- <mem_counter_N>
+ -- <swap_counter_N>
+ -- <mem_counter_N1>
| + -- <swap_counter_N1>
+ -- <mem_counter_N2>
+ -- <swap_counter_N2>
>
>> @@ -976,19 +976,22 @@ static void free_mem_cgroup_per_zone_info(struct
>> mem_cgroup *mem, int node)
>> static struct cgroup_subsys_state *
>> mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>> {
>> - struct mem_cgroup *mem;
>> + struct mem_cgroup *mem, *parent;
>> int node;
>>
>> if (unlikely((cont->parent) == NULL)) {
>> mem = &init_mem_cgroup;
>> init_mm.mem_cgroup = mem;
>> - } else
>> + parent = NULL;
>> + } else {
>> mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
>> + parent = mem_cgroup_from_cont(cont->parent);
>> + }
>>
>> if (mem == NULL)
>> return ERR_PTR(-ENOMEM);
>>
>> - res_counter_init(&mem->res);
>> + res_counter_init(&mem->res, parent ? &parent->res : NULL);
>>
> I have no objection to add some hierarchical support to res_counter.
>
> But we should wait to add it to mem_cgroup because we have to add
> some amount of codes to handle hierarchy under mem_cgroup in reasonable way.
> for example)
> - hierarchical memory reclaim
> - keeping fairness between sub memory controllers.
> etc...
>
> Thanks,
> -Kame
>
>
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