[Devel] Re: [PATCH v3 05/13] Add a __GFP_KMEMCG flag

[Glauber Costa]

On 09/27/2012 05:34 PM, Mel Gorman wrote:
> On Tue, Sep 18, 2012 at 06:04:02PM +0400, Glauber Costa wrote:
>> This flag is used to indicate to the callees that this allocation is a
>> kernel allocation in process context, and should be accounted to
>> current's memcg. It takes numerical place of the of the recently removed
>> __GFP_NO_KSWAPD.
>>
>> Signed-off-by: Glauber Costa <glommer at parallels.com>
>> CC: Christoph Lameter <cl at linux.com>
>> CC: Pekka Enberg <penberg at cs.helsinki.fi>
>> CC: Michal Hocko <mhocko at suse.cz>
>> CC: Johannes Weiner <hannes at cmpxchg.org>
>> CC: Suleiman Souhlal <suleiman at google.com>
>> CC: Rik van Riel <riel at redhat.com>
>> CC: Mel Gorman <mel at csn.ul.ie>
>> Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
> 
> I agree with Christophs recommendation that this flag always exist instead
> of being 0 in the !MEMCG_KMEM case. If __GFP_KMEMCG ever is used in another
> part of the VM (which would be unexpected but still) then the behaviour
> might differ too much between MEMCG_KMEM and !MEMCG_KMEM cases. As unlikely
> as the case is, it's not impossible.
> 
> For tracing __GFP_KMEMCG should have an entry in
> include/trace/events/gfpflags.h
> 
> Get rid of the CONFIG_MEMCG_KMEM check and update
> include/trace/events/gfpflags.h and then feel free to stick my Acked-by
> on it.
> 

Thanks, that is certainly doable.