Re: [PATCH v2 0/6] memcg: disable swap cgroup allocation at swapon

[Jeff Liu <jeff.liu@oracle.com>]

On 01/29/2013 11:15 PM, Michal Hocko wrote:
> On Mon 28-01-13 18:54:27, Jeff Liu wrote:
>> Hello,
>>
>> Here is the v2 patch set for disabling swap_cgroup structures allocation
>> per swapon.
>>
>> In the initial version, one big issue is that I have missed the swap tracking
>> for the root memcg, thanks Michal pointing it out. :)
>>
>> In order to solve it, the easiest approach I can think out is to bypass the root
>> memcg swap accounting during the business and figure it out with some global stats,
>> which means that we always return 0 per root memcg swap charge/uncharge stage, and
>> this is inspired by another proposal from Zhengju:
>> "memcg: Don't account root memcg page statistics -- https://lkml.org/lkml/2013/1/2/71"
>>
>> Besides that, another major fix is deallocate swap accounting structures on the last
>> non-root memcg remove after all references to it are gone rather than doing it on
>> mem_cgroup_destroy().
>>
>> Any comment are welcome!
> 
> Could you also post your testing methodology and results, please? It
> would be also really great if you could sum up memory savings.
Sure, I'll post those info in the next try, and will revisit [PATCH v2
2/6] and answer the comments from you and Glauber since my head is not
very clear now. :)
> 
> Anyway thanks this second version looks really promising.
Thanks for your kind review, have a nice day!

-Jeff
> 
>> v1->v2:
>> - Refactor swap_cgroup_swapon()/swap_cgroup_prepare(), to make the later can be
>>   used for allocating buffers per the first non-root memcg creation.
>> - Bypass root memcg swap statistics, using the global stats to figure it out instead.
>> - Export nr_swap_files which would be used when creating/freeing swap_cgroup
>> - Deallocate swap accounting structures on the last non-root memcg removal
>>
>> Old patch set:
>> v1:
>> http://marc.info/?l=linux-mm&m=135461016823964&w=2
>>
>>
>> Thanks,
>> -Jeff
>>
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