Re: [patch] mm: memcontrol: avoid charge statistics churn during page migration

[Michal Hocko]

On Tue 05-08-14 09:12:23, Johannes Weiner wrote:
> On Tue, Aug 05, 2014 at 02:24:34PM +0200, Michal Hocko wrote:
> > On Mon 04-08-14 16:34:29, Johannes Weiner wrote:
> > > Charge migration currently disables IRQs twice to update the charge
> > > statistics for the old page and then again for the new page.
> > > 
> > > But migration is a seemless transition of a charge from one physical
> > > page to another one of the same size, so this should be a non-event
> > > from an accounting point of view.  Leave the statistics alone.
> > 
> > Moving stats to mem_cgroup_commit_charge sounds logical to me but does
> > this work properly even for the fuse replace page cache case when old
> > and new pages can already live in different memcgs?
> 
> We don't migrate if the new page is already charged.

Right you are.

Acked-by: Michal Hocko <mhocko@xxxxxxx>

-- 
Michal Hocko
SUSE Labs
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