Re: [PATCH v2 1/4] mm: introduce compaction and migration for virtio ballooned pages

[Rafael Aquini <aquini@redhat.com>]

On Fri, Jun 29, 2012 at 04:31:57PM +0100, Mel Gorman wrote:
> On Thu, Jun 28, 2012 at 06:49:39PM -0300, Rafael Aquini wrote:
> > This patch introduces the helper functions as well as the necessary changes
> > to teach compaction and migration bits how to cope with pages which are
> > part of a guest memory balloon, in order to make them movable by memory
> > compaction procedures.
> > 
> > Signed-off-by: Rafael Aquini <aquini@redhat.com>
> 
> I have two minor comments but it is not critical they be addressed. If you
> doa V3 then fix it but if it is picked up as it is, I'm ok with that.
> From a compaction point of view;
> 
> Acked-by: Mel Gorman <mel@csn.ul.ie>
> 
Thanks Mel!

> > ---
> >  include/linux/mm.h |   16 ++++++++
> >  mm/compaction.c    |  110 +++++++++++++++++++++++++++++++++++++++++++---------
> >  mm/migrate.c       |   30 +++++++++++++-
> >  3 files changed, 136 insertions(+), 20 deletions(-)
> > 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index b36d08c..35568fc 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1629,5 +1629,21 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; }
> >  static inline bool page_is_guard(struct page *page) { return false; }
> >  #endif /* CONFIG_DEBUG_PAGEALLOC */
> >  
> > +#if (defined(CONFIG_VIRTIO_BALLOON) || \
> > +	defined(CONFIG_VIRTIO_BALLOON_MODULE)) && defined(CONFIG_COMPACTION)
> > +extern bool isolate_balloon_page(struct page *);
> > +extern bool putback_balloon_page(struct page *);
> > +extern struct address_space *balloon_mapping;
> > +
> > +static inline bool is_balloon_page(struct page *page)
> > +{
> > +        return (page->mapping == balloon_mapping) ? true : false;
> > +}
> > +#else
> > +static inline bool is_balloon_page(struct page *page)       { return false; }
> > +static inline bool isolate_balloon_page(struct page *page)  { return false; }
> > +static inline bool putback_balloon_page(struct page *page)  { return false; }
> > +#endif /* (VIRTIO_BALLOON || VIRTIO_BALLOON_MODULE) && COMPACTION */
> > +
> >  #endif /* __KERNEL__ */
> >  #endif /* _LINUX_MM_H */
> 
> isolate_balloon_page is only used in compaction.c and could declared static
> to compaction.c. You could move them all between struct compact_control
> and release_pages to avoid forward declarations.
> 
Sounds good, will do it.


> > <SNIP>
> > +/* putback_lru_page() counterpart for a ballooned page */
> > +bool putback_balloon_page(struct page *page)
> > +{
> > +	if (WARN_ON(!is_balloon_page(page)))
> > +		return false;
> > +
> > +	if (likely(trylock_page(page))) {
> > +		if(is_balloon_page(page)) {
> 
> Stick a space in there. Run checkpatch.pl if you haven't already. I suspect
> it would have caught this.
> 
Ugh! Sorry, that one has completely escaped me... :( I'll fix it right away.


> As I said, not worth spinning a V3 for :)
> 
I'll respin a v3 to address your suggestions and a couple extra points Minchan
has raised. If anything else pops up to your eyes, please, let me know.

Rafael

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