On Thu, Jul 11, 2013 at 7:56 AM, Michal Hocko <mhocko@xxxxxxx> wrote:
> On Sat 06-07-13 01:33:43, Sha Zhengju wrote:
>> From: Sha Zhengju <handai.szj@xxxxxxxxxx>
>>
>> If memcg is enabled and no non-root memcg exists, all allocated
>> pages belongs to root_mem_cgroup and wil go through root memcg
>> statistics routines. So in order to reduce overheads after adding
>> memcg dirty/writeback accounting in hot paths, we use jump label to
>> patch mem_cgroup_{begin,end}_update_page_stat() in or out when not
>> used.
>
> I do not think this is enough. How much do you save? One atomic read.
> This doesn't seem like a killer.
Given we're already using mem_cgroup_{begin,end}_update_page_stat(),
this optimization seems independent of memcg dirty/writeback
accounting. Does this patch help memcg even before dirty/writeback
accounting? If yes, then we have the option of splitting this
optimization out of the series.
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