On 05/15/2012 06:46 AM, KAMEZAWA Hiroyuki wrote:
> (2012/05/12 2:44), Glauber Costa wrote:
>
>> This patch creates a mechanism that skip memcg allocations during
>> certain pieces of our core code. It basically works in the same way
>> as preempt_disable()/preempt_enable(): By marking a region under
>> which all allocations will be accounted to the root memcg.
>>
>> We need this to prevent races in early cache creation, when we
>> allocate data using caches that are not necessarily created already.
>>
>> Signed-off-by: Glauber Costa<glommer@xxxxxxxxxxxxx>
>> CC: Christoph Lameter<cl@xxxxxxxxx>
>> CC: Pekka Enberg<penberg@xxxxxxxxxxxxxx>
>> CC: Michal Hocko<mhocko@xxxxxxx>
>> CC: Kamezawa Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
>> CC: Johannes Weiner<hannes@xxxxxxxxxxx>
>> CC: Suleiman Souhlal<suleiman@xxxxxxxxxx>
>
>
> The concept seems okay to me but...
>
>> ---
>> include/linux/sched.h | 1 +
>> mm/memcontrol.c | 25 +++++++++++++++++++++++++
>> 2 files changed, 26 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 81a173c..0501114 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -1613,6 +1613,7 @@ struct task_struct {
>> unsigned long nr_pages; /* uncharged usage */
>> unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
>> } memcg_batch;
>> + atomic_t memcg_kmem_skip_account;
>
>
> If only 'current' thread touch this, you don't need to make this atomic counter.
> you can use 'long'.
>
You're absolutely right, Kame, thanks.
I first used atomic_t because I had it tested against current->mm->owner.
Do you, btw, agree to use current instead of owner here?
You can find the rationale in earlier mails between me and Suleiman.
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