linux-kernel - Re: [RFC][PATCH 02/10] zsmalloc: always keep per-class stats

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Date:	Thu, 4 Jun 2015 11:18:21 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCH 02/10] zsmalloc: always keep per-class stats

On Sat, May 30, 2015 at 12:05:20AM +0900, Sergey Senozhatsky wrote:
> always account per-class `zs_size_stat' stats. this data will
> help us make better decisions during compaction. we are especially
> interested in OBJ_ALLOCATED and OBJ_USED, which can tell us if
> class compaction will result in any memory gain.
> 
> for instance, we know the number of allocated objects in the class,
> the number of objects being used (so we also know how many objects
> are not used) and the number of objects per-page. so we can estimate
> how many pages compaction can free (pages that will turn into
> ZS_EMPTY during compaction).

Fair enough but I need to read further patches to see if we need
really this at the moment.

I hope it would be better to write down more detail in cover-letter
so when I read just [0/0] I realize your goal and approach without
looking into detail in each patch.

> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> ---
>  mm/zsmalloc.c | 49 ++++++++++++-------------------------------------
>  1 file changed, 12 insertions(+), 37 deletions(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index e615b31..778b8db 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -169,14 +169,12 @@ enum zs_stat_type {
>  	NR_ZS_STAT_TYPE,
>  };
>  
> -#ifdef CONFIG_ZSMALLOC_STAT
> -
> -static struct dentry *zs_stat_root;
> -
>  struct zs_size_stat {
>  	unsigned long objs[NR_ZS_STAT_TYPE];
>  };
>  
> +#ifdef CONFIG_ZSMALLOC_STAT
> +static struct dentry *zs_stat_root;
>  #endif
>  
>  /*
> @@ -201,25 +199,21 @@ static int zs_size_classes;
>  static const int fullness_threshold_frac = 4;
>  
>  struct size_class {
> +	spinlock_t		lock;
> +	struct page		*fullness_list[_ZS_NR_FULLNESS_GROUPS];
>  	/*
>  	 * Size of objects stored in this class. Must be multiple
>  	 * of ZS_ALIGN.
>  	 */
> -	int size;
> -	unsigned int index;
> +	int			size;
> +	unsigned int		index;
>  
>  	/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
> -	int pages_per_zspage;
> -	/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
> -	bool huge;
> -
> -#ifdef CONFIG_ZSMALLOC_STAT
> -	struct zs_size_stat stats;
> -#endif
> -
> -	spinlock_t lock;
> +	int			pages_per_zspage;
> +	struct zs_size_stat	stats;
>  
> -	struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS];
> +	/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
> +	bool			huge;
>  };
>  
>  /*
> @@ -439,8 +433,6 @@ static int get_size_class_index(int size)
>  	return min(zs_size_classes - 1, idx);
>  }
>  
> -#ifdef CONFIG_ZSMALLOC_STAT
> -
>  static inline void zs_stat_inc(struct size_class *class,
>  				enum zs_stat_type type, unsigned long cnt)
>  {
> @@ -459,6 +451,8 @@ static inline unsigned long zs_stat_get(struct size_class *class,
>  	return class->stats.objs[type];
>  }
>  
> +#ifdef CONFIG_ZSMALLOC_STAT
> +
>  static int __init zs_stat_init(void)
>  {
>  	if (!debugfs_initialized())
> @@ -574,23 +568,6 @@ static void zs_pool_stat_destroy(struct zs_pool *pool)
>  }
>  
>  #else /* CONFIG_ZSMALLOC_STAT */
> -
> -static inline void zs_stat_inc(struct size_class *class,
> -				enum zs_stat_type type, unsigned long cnt)
> -{
> -}
> -
> -static inline void zs_stat_dec(struct size_class *class,
> -				enum zs_stat_type type, unsigned long cnt)
> -{
> -}
> -
> -static inline unsigned long zs_stat_get(struct size_class *class,
> -				enum zs_stat_type type)
> -{
> -	return 0;
> -}
> -
>  static int __init zs_stat_init(void)
>  {
>  	return 0;
> @@ -608,7 +585,6 @@ static inline int zs_pool_stat_create(char *name, struct zs_pool *pool)
>  static inline void zs_pool_stat_destroy(struct zs_pool *pool)
>  {
>  }
> -
>  #endif
>  
>  
> @@ -1682,7 +1658,6 @@ static void putback_zspage(struct zs_pool *pool, struct size_class *class,
>  			class->size, class->pages_per_zspage));
>  		atomic_long_sub(class->pages_per_zspage,
>  				&pool->pages_allocated);
> -
>  		free_zspage(first_page);
>  	}
>  }
> -- 
> 2.4.2.337.gfae46aa
> 

-- 
Kind regards,
Minchan Kim
--
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