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SubjectRe: [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages
On Thu, 25 Mar 2010 18:09:34 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> > On Thu, 25 Mar 2010 08:32:35 +0000
> > Mel Gorman <mel@csn.ul.ie> 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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