Re: [PATCH v3 07/11] memcg: add dirty limits to mem_cgroup

Greg Thelen
2010-10-20T04:08:33Z

Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> writes:

>> +static unsigned long long
>> +memcg_hierarchical_free_pages(struct mem_cgroup *mem)
>> +{
>> + struct cgroup *cgroup;
>> + unsigned long long min_free, free;
>> +
>> + min_free = res_counter_read_u64(&mem->res, RES_LIMIT) -
>> + res_counter_read_u64(&mem->res, RES_USAGE);
>> + cgroup = mem->css.cgroup;
>> + if (!mem->use_hierarchy)
>> + goto out;
>> +
>> + while (cgroup->parent) {
>> + cgroup = cgroup->parent;
>> + mem = mem_cgroup_from_cont(cgroup);
>> + if (!mem->use_hierarchy)
>> + break;
>> + free = res_counter_read_u64(&mem->res, RES_LIMIT) -
>> + res_counter_read_u64(&mem->res, RES_USAGE);
>> + min_free = min(min_free, free);
>> + }
>> +out:
>> + /* Translate free memory in pages */
>> + return min_free >> PAGE_SHIFT;
>> +}
>> +
> I think you can simplify this function using parent_mem_cgroup().
>
> unsigned long free, min_free = ULLONG_MAX;
>
> while (mem) {
> free = res_counter_read_u64(&mem->res, RES_LIMIT) -
> res_counter_read_u64(&mem->res, RES_USAGE);
> min_free = min(min_free, free);
> mem = parent_mem_cgroup();
> }
>
> /* Translate free memory in pages */
> return min_free >> PAGE_SHIFT;
>
> And, IMHO, we should return min(global_page_state(NR_FREE_PAGES), min_free >> PAGE_SHIFT).
> Because we are allowed to set no-limit(or a very big limit) in memcg,
> so min_free can be very big if we don't set a limit against all the memcg's in hierarchy.
>
>
> Thanks,
> Dasiuke Nishimura.

Thank you. This is a good suggestion. I will update the page to include this.

--
Greg