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

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Date:	Tue, 28 Feb 2012 10:09:49 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Hugh Dickins <hughd@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v3 06/21] mm: lruvec linking functions

KAMEZAWA Hiroyuki wrote:
> On Thu, 23 Feb 2012 17:52:04 +0400
> Konstantin Khlebnikov<khlebnikov@...nvz.org>  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@...nvz.org>
>
> 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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