Re: [PATCH v2 1/7] Basic kernel memory functionality for the Memory Controller

Glauber Costa
2011-09-18T19:12:08Z

On 09/18/2011 04:05 PM, Kirill A. Shutemov wrote:
> On Sun, Sep 18, 2011 at 12:39:12AM -0300, Glauber Costa wrote:
>>> No kernel memory accounting for root cgroup, right?
>> Not sure. Maybe kernel memory accounting is useful even for root cgroup.
>> Same as normal memory accounting... what we want to avoid is kernel
>> memory limits. OTOH, if we are not limiting it anyway, accounting it is
>> just useless overhead... Even the statistics can then be gathered
>> through all
>> the proc files that show slab usage, I guess?
>
> It's better to leave root cgroup without accounting. At least for now.
> We can add it later if needed.

Fair.

>>>
>>>> @@ -3979,6 +3999,10 @@ static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
>>>> else
>>>> val = res_counter_read_u64(&mem->memsw, name);
>>>> break;
>>>> + case _KMEM:
>>>> + val = res_counter_read_u64(&mem->kmem, name);
>>>> + break;
>>>> +
>>>
>>> Always zero in root cgroup?
>>
>> Yes, if we're not accounting, it should be zero. WARN_ON, maybe?
>
> -ENOSYS?
>
I'd personally prefer WARN_ON. It is good symmetry from userspace PoV to
always be able to get a value out of it. Also, it something goes wrong
and it is not zero for some reason, this will help us find it.