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

[Daisuke Nishimura]

On Wed, 11 Jun 2008 13:14:37 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com> wrote:
> On Wed, 11 Jun 2008 12:44:46 +0900 (JST)
> yamamoto at 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.
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