Re: [RFD][PATCH] memcg: Move Usage at Task Move

Daisuke Nishimura
2008-06-11T04:29:09Z

On Wed, 11 Jun 2008 13:14:37 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Wed, 11 Jun 2008 12:44:46 +0900 (JST)
> yamamoto@valinux.co.jp (YAMAMOTO Takashi) wrote:
>
> > > I'm now considering following logic. How do you think ?
> > >
> > > Assume: move TASK from group:CURR to group:DEST.
> > >
> > > == move_task(TASK, CURR, DEST)
> > >
> > > if (DEST's limit is unlimited)
> > > moving TASK
> > > return success.
> > >
> > > usage = check_usage_of_task(TASK).
> > >
> > > /* try to reserve enough room in destionation */
> > > if (try_to_reserve_enough_room(DEST, usage)) {
> > > move TASK to DEST and move pages AMAP.
> > > /* usage_of_task(TASK) can be changed while we do this.
> > > Then, we move AMAP. */
> > > return success;
> > > }
> > > return failure.
> > > ==
> >
> > AMAP means that you might leave some random charges in CURR?
> >
> yes. but we can reduce bad case by some way
> - reserve more than necessary.
> or
> - read_lock mm->sem while move.
>
I preffer the latter.
Though it's expencive, I think moving a task would not happen
so offen.

Thanks,
Daisuke Nishimura.