Re: [RFC][PATCH 4/7][memcg] memcg use ID in page_cgroup

[Vivek Goyal]

On Wed, Jul 28, 2010 at 12:21:28PM +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 28 Jul 2010 12:18:20 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
>  
> > > > Hmm, but page-allocation-time doesn't sound very good for me.
> > > > 
> > > 
> > > Why?
> > > 
> > 
> > As you wrote, by attaching ID when a page cache is added, we'll have
> > much chances of free-rider until it's paged out. So, adding some
> > reseting-owner point may be good. 
> > 
> > But considering real world usage, I may be wrong.
> > There will not be much free rider in real world, especially at write().
> > Then, page-allocation time may be good.
> > 
> > (Because database doesn't use page-cache, there will be no big random write
> >  application.)
> > 
> 
> Sorry, one more reason. memory cgroup has much complex code for supporting
> move_account, re-attaching memory cgroup per pages.
> So, if you take care of task-move-between-groups, blkio-ID may have
> some problems if you only support allocation-time accounting.

I think initially we can just keep it simple for blkio controller and
not move page charges across blkio cgroup when process moves.

Vivek
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