Michal Hocko Messages: 109 Registered: December 2011
Senior Member
On Fri 17-08-12 11:01:06, Glauber Costa wrote:
> On 08/17/2012 11:02 AM, Michal Hocko wrote:
> > On Thu 09-08-12 17:01:16, Glauber Costa wrote:
> >> We can use jump labels to patch the code in or out when not used.
> >>
> >> Because the assignment: memcg->kmem_accounted = true is done after the
> >> jump labels increment, we guarantee that the root memcg will always be
> >> selected until all call sites are patched (see memcg_kmem_enabled).
> >
> > Not that it would be really important because kmem_accounted goes away
And just found out it doesn't go away completely, it just transforms
from bool to unsigned log (with flags). The rest still holds...
> > in a subsequent patch but I think the wording is a bit misleading here.
> > First of all there is no guanratee that kmem_accounted=true is seen
> > before atomic_inc(&key->enabled) because there is no memory barrier and
> > the lock serves just a leave barrier. But I do not think this is
> > important at all because key->enabled is what matters here. Even if
> > memcg_kmem_enabled is true we do not consider it if the key is disabled,
> > right?
> >
>
> Right.
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