Re: [PATCH v3 06/21] mm: lruvec linking functions

[Konstantin Khlebnikov]

KAMEZAWA Hiroyuki wrote:
> On Thu, 23 Feb 2012 17:52:04 +0400
> Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>  wrote:
>
> > This patch adds links from page to its lruvec and from lruvec to its zone and node.
> > If CONFIG_CGROUP_MEM_RES_CTLR=n they just page_zone() and container_of().
> >
> > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
>
> small comments in below.
>
> > ---
> >   include/linux/mm.h     |   37 +++++++++++++++++++++++++++++++++++++
> >   include/linux/mmzone.h |   12 ++++++++----
> >   mm/internal.h          |    1 +
> >   mm/memcontrol.c        |   27 ++++++++++++++++++++++++---
> >   mm/page_alloc.c        |   17 ++++++++++++++---
> >   5 files changed, 84 insertions(+), 10 deletions(-)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index ee3ebc1..c6dc4ab 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -728,6 +728,43 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
> >   #endif
> >   }
> >
> > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > +
> > +/* Multiple lruvecs in zone */
> > +
> > +extern struct lruvec *page_lruvec(struct page *page);
> > +
> > +static inline struct zone *lruvec_zone(struct lruvec *lruvec)
> > +{
> > +	return lruvec->zone;
> > +}
> > +
> > +static inline struct pglist_data *lruvec_node(struct lruvec *lruvec)
> > +{
> > +	return lruvec->node;
> > +}
> > +
> > +#else /* CONFIG_CGROUP_MEM_RES_CTLR */
> > +
> > +/* Single lruvec in zone */
> > +
> > +static inline struct lruvec *page_lruvec(struct page *page)
> > +{
> > +	return&page_zone(page)->lruvec;
> > +}
> > +
> > +static inline struct zone *lruvec_zone(struct lruvec *lruvec)
> > +{
> > +	return container_of(lruvec, struct zone, lruvec);
> > +}
> > +
> > +static inline struct pglist_data *lruvec_node(struct lruvec *lruvec)
> > +{
> > +	return lruvec_zone(lruvec)->zone_pgdat;
> > +}
> > +
> > +#endif /* CONFIG_CGROUP_MEM_RES_CTLR */
> > +
> >   /*
> >    * Some inline functions in vmstat.h depend on page_zone()
> >    */
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index ddd0fd2..be8873a 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -159,10 +159,6 @@ static inline int is_unevictable_lru(enum lru_list lru)
> >   	return (lru == LRU_UNEVICTABLE);
> >   }
> >
> > -struct lruvec {
> > -	struct list_head pages_lru[NR_LRU_LISTS];
> > -};
> > -
> >   /* Mask used at gathering information at once (see memcontrol.c) */
> >   #define LRU_ALL_FILE (BIT(LRU_INACTIVE_FILE) | BIT(LRU_ACTIVE_FILE))
> >   #define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))
> > @@ -300,6 +296,14 @@ struct zone_reclaim_stat {
> >   	unsigned long		recent_scanned[2];
> >   };
> >
> > +struct lruvec {
> > +	struct list_head	pages_lru[NR_LRU_LISTS];
> > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > +	struct zone		*zone;
> > +	struct pglist_data	*node;
> > +#endif
>
> I don't think this #ifdef is very good ....this adds other #ifdefs in other headers.
> How bad if we remove this #ifdef and use ->zone, ->pgdat in lruvec_zone, lruvec_page
> always ?

This adds one dereference in lruvec_zone() if memcg is disabled in config.
We can remove ifdef from declaration and initialization, but keep optimized variant of lruvec_zone()

> There may be concerns to fit lruvec at el into cache-line...but this set will add
> a (big) hash here later..
>
> I'm sorry if you're asked to add this #ifdef in v1 or v2.
>
> Thanks,
> -Kame

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