Re: [RFC][PATCH 0/1] Node-based reclaim/migration

["Paul Menage" <menage@google.com>]

On 11/30/06, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> > How does kswapd do this safely?
> >
> kswapd doesn't touches page->mapping after page_mapcount() goes down to 0.

OK, so we could do the same, and just assume that pages with a
page_mapcount() of 0 are either about to be freed or can be picked up
on a later migration sweep. Is it common for a page to have a 0
page_mapcount() for a long period of time without being freed or
remapped?

>
> I think one of the biggest concern will be performance impact. And this will
> touch objrmap core, it is good to start discussion with a patch.
>

I'll have a go. My initial thought is that the only performance impact
on the rmap core would be that unlink_anon_vma() would need one extra
check when determining whether to free an anon_vma

Paul

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