On 7/12/24 3:27 PM, Vlastimil Babka wrote:
>> I checked the history of slab for this part. It introduced
>> from commit 10befea91b61c ("mm: memcg/slab: use a single set of kmem_caches for all allocations")
>> But still don't know why !page_has_obj_cgroups followed by memcg_alloc_page_obj_cgroups. Anyone like
>> to give a hints?
>>
>> page = virt_to_head_page(p[i]);
>> +
>> + if (!page_has_obj_cgroups(page) &&
>> + memcg_alloc_page_obj_cgroups(page, s, flags)) {
>> + obj_cgroup_uncharge(objcg, obj_full_size(s));
>> + continue;
>> + }
> I'm not sure I understand your question. The code is trying to charge the
> allocation to a memcg and use the objext.memcg to associate that memcg to
> the object so it can be properly uncharged when freeing.
> When it's the first object in the particular slab page to be charged, the
> objext may not be yet allocated, so it has has to be allocated at that point.
I see. Thanks for explanation!
