Re: [PATCH 02/11] mm,migration: Do not try to migrate unmappedanonymous pages

[KAMEZAWA Hiroyuki]

On Thu, 25 Mar 2010 18:09:34 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:

> > On Thu, 25 Mar 2010 08:32:35 +0000
> > Mel Gorman <mel@xxxxxxxxx> wrote:

> >  IIUC, the race in memory-hotunplug was fixed by this patch [2/11].
> > 
> >  But, this behavior of unmap_and_move() requires access to _freed_
> >  objects (spinlock). Even if it's safe because of SLAB_DESTROY_BY_RCU,
> >  it't not good habit in general.
> > 
> >  After direct compaction, page-migration will be one of "core" code of
> >  memory management. Then, I agree to patch [1/11] as our direction for
> >  keeping sanity and showing direction to more updates. Maybe adding
> >  refcnt and removing RCU in futuer is good.
> 
> But Christoph seems oppose to remove SLAB_DESTROY_BY_RCU. then refcount
> is meaningless now. I agree you if we will remove SLAB_DESTROY_BY_RCU
> in the future.
> 
removing rcu_read_lock/unlock in unmap_and_move() and removing
SLAB_DESTROY_BY_RCU is different story.

Thanks,
-Kame

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