On 06/08/2012 11:31 PM, Christoph Lameter wrote:

Please make this conditional on CONFIG_MEMCG or so. The bit can be useful
in particular on 32 bit architectures.

Looking at how __GFP_NOTRACK works - which is also ifdef'd, the bit it 
uses is skipped if that is not defined, which I believe is a sane thing 
to do.

Given that, I don't see the point of conditionally defining the memcg 
bit, It basically means that the only way we can reuse the bit saved is 
by making a future feature fundamentally incompatible with memcg.