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

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Date:	Fri, 2 Mar 2012 14:17:39 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <jweiner@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter

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 ?

>  
> -	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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