Re: [PATCH v3 07/21] mm: add lruvec->pages_count

[Konstantin Khlebnikov]

KAMEZAWA Hiroyuki wrote:
> On Thu, 23 Feb 2012 17:52:08 +0400
> Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>  wrote:
>
> > Move lru pages counter from mem_cgroup_per_zone->count[] to lruvec->pages_count[]
> >
> > Account pages in all lruvecs, incuding root,
> > this isn't a huge overhead, but it greatly simplifies all code.
> >
> > Redundant page_lruvec() calls will be optimized in further patches.
> >
> > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
>
> Hmm, I like this but..a question below.
>
> > ---
> >   include/linux/memcontrol.h |   29 --------------
> >   include/linux/mm_inline.h  |   15 +++++--
> >   include/linux/mmzone.h     |    1
> >   mm/memcontrol.c            |   93 +-------------------------------------------
> >   mm/swap.c                  |    7 +--
> >   mm/vmscan.c                |   25 +++++++++---
> >   6 files changed, 34 insertions(+), 136 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 4822d53..b9d555b 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -63,12 +63,6 @@ extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> >   					gfp_t gfp_mask);
> >
> >   struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
> > -struct lruvec *mem_cgroup_lru_add_list(struct zone *, struct page *,
> > -				       enum lru_list);
> > -void mem_cgroup_lru_del_list(struct page *, enum lru_list);
> > -void mem_cgroup_lru_del(struct page *);
> > -struct lruvec *mem_cgroup_lru_move_lists(struct zone *, struct page *,
> > -					 enum lru_list, enum lru_list);
> >
> >   /* For coalescing uncharge for reducing memcg' overhead*/
> >   extern void mem_cgroup_uncharge_start(void);
> > @@ -212,29 +206,6 @@ static inline struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
> >   	return&zone->lruvec;
> >   }
> >
> > -static inline struct lruvec *mem_cgroup_lru_add_list(struct zone *zone,
> > -						     struct page *page,
> > -						     enum lru_list lru)
> > -{
> > -	return&zone->lruvec;
> > -}
> > -
> > -static inline void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru)
> > -{
> > -}
> > -
> > -static inline void mem_cgroup_lru_del(struct page *page)
> > -{
> > -}
> > -
> > -static inline struct lruvec *mem_cgroup_lru_move_lists(struct zone *zone,
> > -						       struct page *page,
> > -						       enum lru_list from,
> > -						       enum lru_list to)
> > -{
> > -	return&zone->lruvec;
> > -}
> > -
> >   static inline struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> >   {
> >   	return NULL;
> > diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> > index 8415596..daa3d15 100644
> > --- a/include/linux/mm_inline.h
> > +++ b/include/linux/mm_inline.h
> > @@ -24,19 +24,24 @@ static inline int page_is_file_cache(struct page *page)
> >   static inline void
> >   add_page_to_lru_list(struct zone *zone, struct page *page, enum lru_list lru)
> >   {
> > -	struct lruvec *lruvec;
> > +	struct lruvec *lruvec = page_lruvec(page);
> > +	int numpages = hpage_nr_pages(page);
> >
> > -	lruvec = mem_cgroup_lru_add_list(zone, page, lru);
> >   	list_add(&page->lru,&lruvec->pages_lru[lru]);
> > -	__mod_zone_page_state(zone, NR_LRU_BASE + lru, hpage_nr_pages(page));
> > +	lruvec->pages_count[lru] += numpages;
> > +	__mod_zone_page_state(zone, NR_LRU_BASE + lru, numpages);
> >   }
> >
> >   static inline void
> >   del_page_from_lru_list(struct zone *zone, struct page *page, enum lru_list lru)
> >   {
> > -	mem_cgroup_lru_del_list(page, lru);
> > +	struct lruvec *lruvec = page_lruvec(page);
> > +	int numpages = hpage_nr_pages(page);
> > +
> >   	list_del(&page->lru);
> > -	__mod_zone_page_state(zone, NR_LRU_BASE + lru, -hpage_nr_pages(page));
> > +	lruvec->pages_count[lru] -= numpages;
> > +	VM_BUG_ON((long)lruvec->pages_count[lru]<  0);
> > +	__mod_zone_page_state(zone, NR_LRU_BASE + lru, -numpages);
> >   }
> >
> >   /**
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index be8873a..69b0f31 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -298,6 +298,7 @@ struct zone_reclaim_stat {
> >
> >   struct lruvec {
> >   	struct list_head	pages_lru[NR_LRU_LISTS];
> > +	unsigned long		pages_count[NR_LRU_LISTS];
>
> In this time, you don't put the objects under #ifdef...why ?

It will make the code much uglier and does not speed up it at all.

> How do you handle duplication "the number of pages in LRU" of zone->vm_stat and this ?

I don't think this is totally bad, vmstat usually has per-cpu drift, these numbers will be exact.

> Thanks,
> -Kame

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