linux-kernel - Re: [PATCH 3/7] mm: rework __isolate_lru

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Date:	Fri, 02 Mar 2012 09:51:27 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <jweiner@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter

KAMEZAWA Hiroyuki wrote:
> On Wed, 29 Feb 2012 13:15:47 +0400
> Konstantin Khlebnikov<khlebnikov@...nvz.org>  wrote:
>
>> This patch adds file/anon filter bits into isolate_mode_t,
>> this allows to simplify checks in __isolate_lru_page().
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>
> Hmm.. I like idea but..
>
>> ---
>>   include/linux/mmzone.h |    4 ++++
>>   include/linux/swap.h   |    2 +-
>>   mm/compaction.c        |    5 +++--
>>   mm/vmscan.c            |   27 +++++++++++++--------------
>>   4 files changed, 21 insertions(+), 17 deletions(-)
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index eff4918..2fed935 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -193,6 +193,10 @@ struct lruvec {
>>   #define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x8)
>>   /* Isolate for asynchronous migration */
>>   #define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x10)
>> +/* Isolate swap-backed pages */
>> +#define	ISOLATE_ANON		((__force isolate_mode_t)0x20)
>> +/* Isolate file-backed pages */
>> +#define	ISOLATE_FILE		((__force isolate_mode_t)0x40)
>>
>>   /* LRU Isolation modes. */
>>   typedef unsigned __bitwise__ isolate_mode_t;
>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>> index ba2c8d7..dc6e6a3 100644
>> --- a/include/linux/swap.h
>> +++ b/include/linux/swap.h
>> @@ -254,7 +254,7 @@ static inline void lru_cache_add_file(struct page *page)
>>   /* linux/mm/vmscan.c */
>>   extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
>>   					gfp_t gfp_mask, nodemask_t *mask);
>> -extern int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file);
>> +extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
>>   extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
>>   						  gfp_t gfp_mask, bool noswap);
>>   extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 74a8c82..cc054f7 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -261,7 +261,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
>>   	unsigned long last_pageblock_nr = 0, pageblock_nr;
>>   	unsigned long nr_scanned = 0, nr_isolated = 0;
>>   	struct list_head *migratelist =&cc->migratepages;
>> -	isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
>> +	isolate_mode_t mode = ISOLATE_ACTIVE | ISOLATE_INACTIVE |
>> +			      ISOLATE_FILE | ISOLATE_ANON;
>>
>>   	/* Do not scan outside zone boundaries */
>>   	low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
>> @@ -375,7 +376,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
>>   			mode |= ISOLATE_ASYNC_MIGRATE;
>>
>>   		/* Try isolate the page */
>> -		if (__isolate_lru_page(page, mode, 0) != 0)
>> +		if (__isolate_lru_page(page, mode) != 0)
>>   			continue;
>>
>>   		VM_BUG_ON(PageTransCompound(page));
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index af6cfe7..1b70338 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1029,27 +1029,18 @@ keep_lumpy:
>>    *
>>    * returns 0 on success, -ve errno on failure.
>>    */
>> -int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
>> +int __isolate_lru_page(struct page *page, isolate_mode_t mode)
>>   {
>> -	bool all_lru_mode;
>>   	int ret = -EINVAL;
>>
>>   	/* Only take pages on the LRU. */
>>   	if (!PageLRU(page))
>>   		return ret;
>>
>> -	all_lru_mode = (mode&  (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
>> -		(ISOLATE_ACTIVE|ISOLATE_INACTIVE);
>> -
>> -	/*
>> -	 * When checking the active state, we need to be sure we are
>> -	 * dealing with comparible boolean values.  Take the logical not
>> -	 * of each.
>> -	 */
>> -	if (!all_lru_mode&&  !PageActive(page) != !(mode&  ISOLATE_ACTIVE))
>> +	if (!(mode&  (PageActive(page) ? ISOLATE_ACTIVE : ISOLATE_INACTIVE)))
>>   		return ret;
>
> Isn't this complicated ?

But it doesn't blows my mind as old code does =)

Maybe someone can propose more clear variant?

>
>>
>> -	if (!all_lru_mode&&  !!page_is_file_cache(page) != file)
>> +	if (!(mode&  (page_is_file_cache(page) ? ISOLATE_FILE : ISOLATE_ANON)))
>>   		return ret;
>>
>>   	/*
>
> ditto.
>
> Where is simple  ?
>
> Thanks,
> -Kame
>

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