On 08/17/2012 01:35 PM, Michal Hocko wrote:

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Above you said "Once enabled, can't be disabled." and now you can

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disable it? Say you are a leaf group with non accounted parents. This
will clear the flag and so no further accounting is done. Shouldn't
unlimited mean that we will never reach the limit? Or am I missing
something?

You are missing something, and maybe I should be more clear about that.
The static branches can't be disabled (it is only safe to disable them
from disarm_static_branches(), when all references are gone). Note that
when unlimited, we flip bits, do a transversal, but there is no mention
to the static branch.

My little brain still doesn't get this. I wasn't concerned about static
branches. I was worried about memcg_can_account_kmem which will return
false now, doesn't it.

Yes, it will. If I got you right, you are concerned because I said that
can't happen. But it will.

But I never said that can't happen. I said (ok, I meant) the static
branches can't be disabled.