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SubjectRe: [RFC] Shared page accounting for memory cgroup
* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-01-06 16:12:11]:

> On Wed, 6 Jan 2010 12:31:50 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> > > No. If it takes long time, locking fork()/exit() for such long time is the bigger
> > > issue.
> > > I recommend you to add memacct subsystem to sum up RSS of all processes's RSS counting
> > > under a cgroup. Althoght it may add huge costs in page fault path but implementation
> > > will be very simple and will not hurt realtime ops.
> > > There will be no terrible race, I guess.
> > >
> >
> > But others hold that lock as well, simple thing like listing tasks and
> > moving tasks, etc. I expect the usage of shared to be in the same
> > range.
> >
>
> And piles up costs ? I think cgroup guys should pay attention to fork/exit
> costs more. Now, it gets slower and slower.
> In that point, I never like migrate-at-task-move work in cpuset and memcg.
>
> My 1st objection to this patch is this "shared" doesn't mean "shared between
> cgroup" but means "shared between processes".
> I think it's of no use and no help to users.
>

So what in your opinion would help end users? My concern is that as
we make progress with memcg, we account only for privately used pages
with no hint/data about the real usage (shared within or with other
cgroups). How do we decide if one cgroup is really heavy?

> And implementation is 2nd thing.
>

More details on your concern, please!

--
Balbir


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